Fundamentals of hydraulics and heat engineering for college. Fundamentals of hydraulics and heat engineering. Monitoring and evaluation of results Mastering the academic discipline

Regional budgetary educational institution

secondary vocational education

"Kursk Assembly College"

WORKING PROGRAM OF THE EDUCATIONAL DISCIPLINE

OP 06.

the main professional educational program of secondary vocational education in the specialty

140102 Heat supply and heat engineering equipment

(basic training)

Kursk

REVIEWED AND APPROVED

at a meeting of the Central Committee of the OPD

Protocol No._____

"____" _____________ 2012

Chairman of the Central Committee Stanar A.M.

AGREED

__________________

Deputy Director for SD O.B. Grunev

"____" ______________ 2012

Work program of the discipline"Theoretical Foundations of Heat Engineering and Hydraulics" developed on the basis of:

Federal state educational standard in the specialty of secondary vocational education(basic training), which is part of the enlarged group of specialties 140000 Energy, power engineering and electrical engineering, approved by order of the Ministry of Education and Science of the Russian Federation dated February 15, 2010, No. 114.

Developer:

A.A. Katalnikova, teacher of OBOU SPO "Kursk Assembly College".

CONTENT

page

PASSPORT OF THE WORKING PROGRAM OF THE EDUCATIONAL DISCIPLINE

STRUCTURE and content of the EDUCATIONAL DISCIPLINE

conditions for the implementation of the work program of the academic discipline

Monitoring and evaluation of results Mastering the academic discipline

1. passport of the working PROGRAM of the EDUCATIONAL DISCIPLINE

Theoretical foundations of heat engineering and hydraulics

1.1. Scope of the work program

The work program of the academic discipline is part of the main professional educational program in accordance with the Federal State Educational Standard in the specialty SPO140102 "Heat supply and heat engineering equipment" (basic training), which is part of the enlarged group of specialties 140000 Power engineering, power engineering and electrical engineering.

The work program of the academic discipline can be used in additional vocational education and training of employees in the field of heat supply and heat engineering equipmentin the presence of secondary (complete) general education. Work experience is not required.

1.2. The place of the academic discipline in the structure of the main professional educational program: discipline is in professional cycle, refers to general professional disciplines.

1.3. Goals and objectives of the academic discipline - requirements for the results of mastering the academic discipline.

be able to :

perform thermal calculations:

Thermodynamic cycles of heat engines and thermal power plants;

fuel consumption; heat and steam for power generation;

Efficiency coefficients of thermodynamic cycles of heat engines and thermal power plants;

Heat loss through building envelopes, insulation of pipelines and heat engineering equipment;

Thermal and material balances, heating surface area of heat exchangers;

Determine the parameters in the hydraulic calculation of pipelines, air ducts;

Build characteristics of pumps and fans.

As a result of mastering the academic discipline, the student mustknow :

Parameters of the state of the thermodynamic system, units of measurement and the relationship between them;

Basic laws of thermodynamics, processes of changing the state of ideal gases, water vapor and water;

Cycles of heat engines and thermal power plants;

Basic laws of heat transfer;

Physical properties of liquids and gases;

Laws of hydrostatics and hydrodynamics;

Main tasks and procedure for hydraulic calculation of pipelines;

Types, devices and characteristics of pumps and fans.

1.4. The number of hours for mastering the work program of the academic discipline:

the maximum study load of a student is 180 hours, including:

obligatory classroom teaching load of the student 120 hours;

independent work of the student 60 hours.

2. STRUCTURE AND CONTENT OF THE EDUCATIONAL DISCIPLINE

2.1. Volume of academic discipline and types of educational work

including:

educational - individual work of the student;

preparation of abstracts;

registration of laboratory work;

systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks;

problem solving, exercise

Final certification in the form exam

2.2. Thematic plan and content of the discipline

Theoretical foundations of heat engineering and hydraulics

A brief historical review and the current level of development of hydraulics and heat engineering.

The role of domestic scientists in the development of these sciences.

Section 1.Physical properties of liquids and gases

Topic 1.1.

Physical properties of liquids and gases

Physical properties of liquids: density, specific gravity, specific volume, the relationship between them, compressibility, viscosity, dependence on temperature and pressure.

Independent work

Section 2. Fundamentals of hydrostatics

Topic 2.1

hydrostatic pressure. Basic equation of hydrostatics.

Forces acting inside the fluid. Hydrostatic pressure at a point, its properties, units of measurement. Absolute and gauge pressure.

Basic equation of hydrostatics. Physical essence and graphic representation of the equation of hydrostatics. Heads. Instruments for measuring pressure..

Laboratory works

Measurement of pressure with a piezometer and manometer. Conversion of pressure units.

Workshops

Solving problems for compiling an equation for the equilibrium of a liquid

Independent work:

Topic 2.2. Forces of liquid and gas pressure on flat and curved walls.

Pascal's law. Hydraulic press, hydraulic jack.

The force of hydrostatic pressure on flat surfaces. center of pressure. hydrostatic paradox. Graphical method for determining the force of hydrostatic pressure

Force of hydrostatic pressure on a cylindrical surface. The formula for calculating pipes for strength. Law of Archimedes. Melting of bodies and their stability.

Workshops

Solving problems of determining the pressure force on various surfaces, determining the thickness of the pipe wall

Independent work of students:

Registration of practical work

Section 3. Fundamentals of hydrodynamics

Topic 3.1. Basic laws of fluid motion

Types of fluid motion: steady, unsteady, uniform, non-uniform. The concept of fluid flow. Fluid flow, flow elements. Velocity and fluid flow. Flow continuity equation.

Bernoulli's equation, its geometric and energetic meaning.

Laboratory works

Study of the Bernoulli equation. Construction of pressure and piezometric lines.

Independent work:

Registration of laboratory works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Topic 3.2. Hydraulic resistance

Hydraulic resistance and their types. Modes of fluid motion.

Reynolds criterion. Characteristics of laminar and turbulent fluid motion. Loss of pressure along the length of the flow and in local resistances (shut-off valves, when expanding and narrowing the flow, changing the direction of the flow). Calculation of head loss in case of sudden expansion of flow. Coefficient of hydraulic friction, its determination in laminar and turbulent modes of fluid motion.

Laboratory works

Determination of two modes of fluid motion. Determination of the Reynolds number.

Determination of head loss along the length, coefficient of hydraulic friction.

Determination of local pressure losses, local resistance coefficient.

Independent work

Registration of laboratory works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks;

Topic 3.3. Hydraulic calculation of pipelines

Pipelines and their types. Hydraulic calculation of simple and complex pipelines. Water hammer in pipelines (direct and indirect).

Calculation of non-pressure and short pipelines.

Workshops

- Calculation of a simple pipeline

Independent work:

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Preparation of abstracts

Approximate topics of abstracts:

Modern methods of protecting pipelines from hydraulic shock.

The phenomenon of cavitation during the flow of liquid in pipes.

Measures applied to prevent cavitation.

Topic 3.4. Fluid flow through holes and nozzles

The flow of liquid from holes at a constant pressure. The concepts of "hole in a thin wall" and "small hole". Types of nozzles. The flow of liquid through nozzles at a constant pressure.

Workshops

Determination of the flow rate of liquid when flowing out of the hole and through the nozzles

Independent work:

- registration of practical work

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks;

Test work on section 3. Fundamentals of hydrodynamics

Section 4 Pumps and fans

Topic 4.1. Types and principle of operation of pumps

Centrifugal pumps, their types, principle of operation. Full head, ultimate suction lift. Feed, pressure, power and efficiency of a centrifugal pump, their definition. The dependence of these parameters on the engine speed.

Proportional formulas. Characteristics of centrifugal pumps and pressure pipelines. Parallel and series operation of centrifugal pumps. Piston pumps, their types, principle of operation. Jet pumps.

Practical work

Characterization of a centrifugal pump

Independent work:

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks;

Educational - individual work of the student.

Topic 4.2. Types and principle of operation of fans

Centrifugal and axial fans, their types and principle of operation. Capacity, pressure, power consumption and fan efficiency. Dependence of fan parameters on engine speed.

Practical work

Construction of characteristics of a centrifugal fan.

Independent work:

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks;

Section 5. Fundamentals of technical thermodynamics

Topic 5.1. Fundamentals of technical thermodynamics. gas laws. gas mixtures.

Thermal and mechanical energy. Basic thermodynamic parameters of the state of the working fluid. Ideal and real gas. Molecular-kinetic theory of gases.

Gas mixture, its composition. Partial pressure and reduced volume of gas mixture components. Dalton's Law. The ratio between the mass and volume compositions of the mixture.

Independent work:

systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Topic 5.2. Heat capacity

Heat capacity and amount of heat. Constant and variable heat capacity. Average and true heat capacity. Heat capacity of the gas mixture

Workshops:

Determination of the volumetric heat capacity of air at constant pressure

Independent work

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Topic 5.3. The laws of thermodynamics. Thermodynamic processes.

The first law of thermodynamics is the law of conservation and transformation of thermal and mechanical energy. Units of measurement of heat and work. Enthalpy of gas. Analysis of the main thermodynamic processes of changing the state of ideal gases: isochoric, isobaric, isothermal, adiabatic, polytropic. The equation of state of thermodynamic processes, their representation on the pv - diagram. Definition of work, change in internal energy and amount of heat.

The second law of thermodynamics. Circular processes or cycles. Thermal efficiency of the cycle. Equilibrium and non-equilibrium state of the working fluid. Reversible and irreversible processes and cycles. The ideal Carnot cycle, its image on the pv - diagram. The second law of thermodynamics for reversible and irreversible processes. Entropy is its physical meaning. Ts-diagram. The third law of thermodynamics.

Workshops:

Thermodynamic calculation of cycles and determination of their thermal efficiency coefficients (COP), depict cycles on pv and Ts - diagrams.

Independent work

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Solving problems, doing exercises

Topic 5.4. Gas cycles

Internal combustion engines. ICE cycles with different methods of heat supply. Their representation on pv and Ts - diagrams. Thermal efficiency of internal combustion engine cycles. Gas turbine installations. Gas turbine cycles with different methods of heat supply. Their representation on pv and Ts - diagrams. Thermal efficiency of gas turbine cycles. Thermodynamic fundamentals of compressor operation. Image of the compressor cycle on pv and Ts - diagrams.

Workshops:

Comparison of thermal efficiency of ICE and GTU cycles with different methods of heat supply.

Independent work

registration of practical work;

Solving problems, doing exercises

Topic 5.5. real gases. Water vapor and its properties

Property of real gases. Characteristic equation of real van der Waals gases. Water vapor is like a real gas. Vaporization, evaporation, boiling, condensation, sublimation, desublimation.

Saturated water vapor. Dry and wet saturated steam. superheated steam. Dryness degree. Humidity and overheating. Boundary curves and critical point. Tables of thermodynamic properties of water and steam.

Workshops:

Determination of steam parameters using tables.

Calculation of wet saturated steam parameters using steam tables and mathematical dependencies.

Independent work

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks;

Topic 5.6. Thermodynamic processes of water vapor

The main processes of changing the state of water vapor: isobaric, isochoric, isothermal and adiabatic. Image of the main thermodynamic processes of water vapor on pv and Ts - diagrams.

Determination of the amount of heat, changes in internal energy, enthalpy, entropy and specific volume of water vapor in each thermodynamic process.

Workshops:

Calculation of the processes of changing the state of water vapor using tables and diagrams.

Independent work

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks;

Solving problems, doing exercises.

Topic 5.7. Expiration and throttling of gases and vapors

General concepts of expiration. Push work and disposable work.

Velocity and critical velocity of the outflow, second mass flow of gas. The dependence of the outflow on the ratio of pressures. Practical application of expiration. Combined Laval nozzle.

The throttling process and its features. Technical application of throttling.

Workshops:

Determination of parameters and characteristics of water vapor during outflow and throttling

Independent work

registration of practical work;

Abstract preparation.

Approximate topics of abstracts:

Combined Laval nozzle;

Practical application of the throttling process;

Technical application of the expiration process.

Topic 5.8. Cycles of steam turbine installations.

Scheme of a steam turbine plant. The Rankine cycle is an ideal steam-water cycle of a thermal power plant, the image of the cycle on pv and Ts - diagrams. Regenerative cycle of a steam turbine plant. Steam reheat cycle. Binary and steam-gas cycles of thermal power plants.

Workshops:

Image of cycles of steam turbine plants on pv and Ts - diagrams

Independent work

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Section 6. Fundamentals of heat transfer

Topic 6.1. Basic provisions of the theory of heat transfer.

The process of heat transfer by conduction, convection and radiation. The concept of heat transfer. Heat transfer through a flat single-layer wall. Fourier law

Heat transfer by thermal conduction through a multilayer flat wall. Heat transfer by thermal conduction through a multilayer cylindrical wall.

Workshops:

Determination of the thermal conductivity coefficient and calculation of the amount of heat transferred by thermal conductivity through walls of various shapes.

Independent work

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Topic 6.2. convective heat transfer. Heat dissipation and heat transfer.

Basic provisions of convective heat transfer. Heat transfer between a flat wall and a liquid. Heat transfer coefficient, its physical meaning Heat transfer through a multilayer wall and cylindrical walls. Heat transfer coefficient, its physical meaning.

Workshops:

Calculation of the amount of heat transferred from the coolant to the walls of various shapes.

Independent work

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Topic 6.3. Heat transfer with free fluid movement, forced longitudinal and transverse flow around pipes, changes in the state of aggregation of matter.

Factors that determine the free movement of fluid. Distribution of temperatures and velocities in the boundary layer. The nature of fluid movement along a vertical wall, near horizontal pipes and plates. The equation for determining the heat transfer coefficient, the conditions for its application.

Heat transfer during longitudinal flow around smooth pipes in turbulent mode. Heat transfer coefficient. The process of heat transfer in the transverse flow around pipes. Chess and in-line arrangement of pipes in bundles. criterion equation.

Conditions for the occurrence of condensation. Thermal resistance during steam condensation. Determination of the heat transfer coefficient during condensation. Boiling condition. The heat transfer coefficient during boiling and its dependence on various factors.

Workshops:

Calculation of the heat transfer coefficient using criterion equations in various cases of convective heat transfer.

Independent work

Registration of practical works;

Problem solving exercises;

Topic 6.4. Basic concepts and laws of thermal radiation. Heat transfer by radiation between bodies.

Properties of thermal radiation. Absorbing, reflecting and transmitting capacity of bodies. Basic laws of thermal radiation: laws of Planck, Stefan-Boltzmann, Lambert, Kirchhoff. Various cases of heat transfer by radiation.

Workshops:

Calculation of the amount of radiant heat, the degree of blackness of the surface of bodies. emissivity and absorption capacity of bodies.

Independent work

Registration of practical works;

Systematic study of class notes, educational and special literature on questions to paragraphs, chapters of textbooks

Topic 6.5. Heat exchangers.

Purpose and classification of heat exchangers. The principle of operation of surface and mixing heat exchangers. The main schemes of movement of heat carriers. Equation of heat balance and heat transfer in a heat exchanger. Heat transfer coefficient of the heat exchanger. Determination of the heating surface of the heat exchanger.

Workshops:

Drawing up the equation of heat balance and heat transfer in heat exchangers.

Independent work

registration of practical work;

Individual educational work of students

Control work in section 6. Fundamentals of heat transfer

To characterize the level of mastering the educational material, the following designations are used:

1. - introductory (recognition of previously studied objects, properties);

2. - reproductive (performance of activities according to a model, instructions or under guidance);

3. - productive (planning and independent performance of activities, solving problematic tasks).

3. conditions for the implementation of the discipline program

3.1. Minimum Logistics Requirements

The implementation of the academic discipline requires the presence of a laboratoryhydraulics, heat engineering and aerodynamics.

Study room equipment:

seats by the number of students;

a teacher's workplace equipped with a personal computer with licensed or free software, relevant sections of the program and connected to the Internet and means of outputting sound information;

a set of teaching aids "Fundamentals of hydraulics, heat engineering and aerodynamics";

three-dimensional models of pumps and fans;

virtual laboratory "Hydraulics";

scanner;

Printer.

Technical training aids:

multimedia projector or multimedia board;

photo and/or video camera;

webcam.

3.2. Information support of training

Main sources:

1. O.N. Bryukhanov, V.A. Zhila. Fundamentals of hydraulics, heat engineering and aerodynamics. - M.: Infra-M, 2010.

2. I.A. Pribytkov, I.A. Levitsky. Theoretical foundations of heat engineering. - M .: Publishing Center "Academy", 2004.

Additional sources:

IN AND. Kalitsun. Hydraulics, water supply and sewerage. – M.: Stroyizdat, 2000.

V.I.Kalitsun, E.V. , K.I. . Fundamentals of hydraulics, heat engineering and aerodynamics. – M.: Stroyizdat, 2005.

V.N. Lukanin. Heat engineering. - M .: Higher School, 1999.

Internet resources:

http://twt.mpei.ru/GDHB/OGTA.html

4. Control and evaluation of the results of mastering the discipline

Monitoring and evaluation the results of mastering the academic discipline is carried out by the teacher in the process of conducting practical classes and laboratory work, testing, as well as the implementation of individual tasks and projects by students.

Learning Outcomes

(learned skills, acquired knowledge)

Forms and methods of monitoring and evaluating learning outcomes

should be able to:

perform thermal calculations:

Thermodynamic cycles of heat engines and thermal power plants;

Protection of practical work

fuel consumption; heat and steam for power generation;

Test work on the topic

Efficiency coefficients of thermodynamic cycles of heat engines and thermal power plants;

Protection of practical work

Heat loss through building envelopes, insulation of pipelines and heat engineering equipment;

Protection of practical work

Thermal and material balances, heating surface area of heat exchangers;

Protection of practical work

Determine the parameters in the hydraulic calculation of pipelines, air ducts;

Test work on the topic

Build characteristics of pumps and fans.

Checking the performance of independent homework

Survey on individual assignments

As a result of mastering the academic discipline, the student must know:

Parameters of the state of the thermodynamic system, units of measurement and the relationship between them;

Basic laws of thermodynamics, processes of changing the state of ideal gases, water vapor and water;

Cycles of heat engines and thermal power plants;

Evaluation of the performance of oral and written exercises

Test

Physical properties of liquids and gases;

Frontal and individual survey during the classroom

Laws of hydrostatics and hydrodynamics;

Evaluation of the frontal and individual survey during the classroom.

Analysis of the results of written testing.

Test

Main tasks and procedure for hydraulic calculation of pipelines;

Independent work check

Types, devices and characteristics of pumps and fans.

Analysis of the results of written testing

Developer:

OBOU SPO "KMT" _________ __ teacher _____ __ A.A. Katalnikova

Experts:

OBOU SPO "KMT" ________ _ Methodist ___ ____ M. G. Denisova _____

____________________ _______ ___________________ _________________________

(place of work) signature (position held) (initials, surname)

The methodical manual "Basic laws of hydraulics" is a short theoretical course that sets out the basic terms and provisions.

The manual is recommended to help students of the specialty "Installation and operation of gas supply systems and equipment" in classroom or extracurricular independent work and the teacher of the disciplines "Fundamentals of hydraulics, heat engineering and aerodynamics", "Hydraulics".

At the end of the manual there is a list of questions for self-study and a list of literature recommended for study.

Download:

Preview:

Methodical development

in the discipline "Fundamentals of hydraulics, heat engineering and aerodynamics":

"Basic laws of hydraulics"

annotation

The methodical manual "Basic laws of hydraulics" is a short theoretical course that sets out the basic terms and provisions.

At the end of the manual there is a list of questions for self-study and a list of literature recommended for study.

Introduction…………………………………………………………………….....4

Hydrostatics, basic concepts………………………………………......5
The basic equation of hydrostatics…………………………………………7
Types of hydrostatic pressure .................................................................... ........eight
Pascal's law, application in practice………………………………...9
Law of Archimedes. Bodies floating condition………………………………..11
Hydrostatic paradox……………………………………………..13
Hydrodynamics, basic concepts………………………………………..14
The equation of continuity (continuity)………………………………16
Bernoulli's equation for an ideal fluid…………………….......17
Bernoulli's equation for a real fluid………………………….20
Questions for self-preparation of students………………..22

Conclusion…………………………………………………………………...23

References……………………………………………………..............24

Introduction

This manual covers the sections "Hydrostatics" and "Hydrodynamics" of the discipline "Fundamentals of hydraulics, heat engineering and aerodynamics". The manual outlines the basic laws of hydraulics, discusses the basic terms and provisions.

The material is presented in accordance with the requirements of the curriculum of this discipline and the educational and methodological complex in the specialty "Installation and operation of gas supply systems and equipment."

The manual is a theoretical course, it can be used in the study of individual topics of the academic discipline, as well as for extracurricular independent work.

Please note that the final stage of this methodological manual is a list of questions for self-preparation of students on all the topics presented.

1. Hydrostatics, basic concepts

Hydrostatics is a branch of hydraulics that studies the laws of equilibrium of fluids and their interaction with bounding surfaces.

Consider a liquid in a state of absolute equilibrium, i.e. at rest. Let us single out some infinitesimal volume inside the liquidΔ V and consider the forces acting on it from the outside.

There are two types of external forces - surface and volumetric (mass).

Surface forces are the forces acting directly on the outer surface of the selected volume of liquid. They are proportional to the area of this surface. Such forces are due to the influence of neighboring volumes of liquid on a given volume or the influence of other bodies.

Volume (mass) forcesare proportional to the mass of the selected volume of liquid and act on all particles inside this volume. Examples of body forces are gravity, centrifugal force, inertia force, etc.

To characterize the internal forces acting on a selected volume of liquid, we introduce a special term. To do this, consider an arbitrary volume of liquid in equilibrium under the action of external forces.

We select a very small area inside this volume of liquid. The force acting on this area is normal (perpendicular) to it, then the ratio:

represents the average hydrostatic pressure occurring at the siteΔω . Otherwise, it can be characterized that under the action of external forces, a stressed state of the liquid occurs, characterized by the occurrence of hydrostatic pressure.

To determine the exact value of p at a given point, it is necessary to determine the limit of this ratio at. which will determine the true hydrostatic pressure at a given point:

The dimension of [p] is equal to the dimension of voltage, i.e.

[p]= [Pa] or [kgf/m 2 ]

Hydrostatic pressure properties

On the outer surface of the liquid, the hydrostatic pressure is always directed along the internal normal, and at any point inside the liquid, its value does not depend on the angle of inclination of the platform on which it acts.

A surface in which the hydrostatic pressure is the same at all points is calledequal pressure surface. These surfaces includefree surface, i.e., the interface between a liquid and a gaseous medium.

Pressure is measured for the purpose of continuous monitoring and timely regulation of all technological parameters. For each technological process, a special regime map is developed. There are cases when, with an uncontrolled increase in pressure, a multi-ton drum of an energy boiler flew away like a soccer ball for several tens of meters, destroying everything in its path. The decrease in pressure does not cause damage, but leads to:

defective products;
fuel overrun.

Basic equation of hydrostatics

Figure 1 - Demonstration of the basic equation of hydrostatics

For any point of a fluid in a state of equilibrium (see Fig. 1), the equality

z+p/γ = z 0 +p 0 /γ = ... = H ,

where p is the pressure at a given point A (see Fig.); p 0 - pressure on the free surface of the liquid; p/γ and p 0 /γ is the height of the liquid columns (with specific gravity γ) corresponding to the pressures at the considered point and on the free surface; z and z 0 - coordinates of point A and the free surface of the liquid relative to an arbitrary horizontal comparison plane (x0y); H - hydrostatic head. From the above formula follows:

p = p 0 +γ(z 0 -z) or p = p 0 +γ h

where h is the immersion depth of the considered point. The above expressions are calledthe basic equation of hydrostatics. The value γ h representsliquid column weight height h.

Conclusion: hydrostatic pressure p at a given point is equal to the sum of the pressure on the free surface of the liquid p 0 and the pressure produced by a liquid column with a height equal to the point's immersion depth.

3. Types of hydrostatic pressure

Hydrostatic pressure is measured in the SI - Pa system. In addition, hydrostatic pressure is measured in kgf/cm 2 , the height of the liquid column (in m water column, mm Hg, etc.) and in physical (atm) and technical (at) atmospheres.

absolute called the pressure created on the body by a single gas without taking into account other atmospheric gases. It is measured in Pa (pascals). Absolute pressure is the sum of atmospheric and gauge pressures.

barometric(atmospheric) refers to the pressure of gravity on all objects in the atmosphere. Normal atmospheric pressure is created by a 760 mm column of mercury at a temperature of 0°C.

vacuum called the negative difference between measured and atmospheric pressure.

Difference between absolute pressure p and atmospheric pressure p a is called excess pressure and is denoted by p hut:

p izb \u003d p - p a

R izb / γ \u003d (p - p a) / γ \u003d h p

h p in this case is calledpiezometric height, which is a measure of excess pressure.

On fig. 2 a) shows a closed reservoir with a liquid, on the surface of which the pressure p 0 . Piezometer connected to the tank P (see figure below) determines the excess pressure at the point BUT .

Absolute and gauge pressures, expressed in atmospheres, are denoted respectively ata and ati.

Vacuum pressure, or vacuum, - lack of pressure to atmospheric (pressure deficit), i.e. the difference between atmospheric or barometric and absolute pressure:

p wak \u003d p a - p

R wack /γ = (p a - p)/γ = h wak

where h vac - vacuum height, i.e. vacuum gauge reading AT connected to the reservoir shown in fig. 2 b). Vacuum is expressed in the same units as pressure, as well as fractions or percentages of the atmosphere.

Figure 2 a - Piezometer readings Figure 2 b - Vacuum gauge readings

From the last two expressions it follows that the vacuum can vary from zero to atmospheric pressure; maximum h value wack at normal atmospheric pressure (760 mm Hg) is equal to 10.33 m of water. Art.

4. Pascal's law, its application in practice

According to the basic equation of hydrostatics, the pressure on the liquid surface p 0 is transmitted to all points of the volume of the liquid and in all directions equally. This is what Pascal's law.

This law was discovered by the French scientist B. Pascal in 1653. It is sometimes called the fundamental law of hydrostatics.

Pascal's law can be explained in terms of the molecular structure of matter. In solids, molecules form a crystal lattice and vibrate around their equilibrium positions. In liquids and gases, molecules are relatively free, they can move relative to each other. It is this feature that allows you to transfer the pressure produced on a liquid (or gas) not only in the direction of the force, but in all directions.

Pascal's law has found wide application in modern technology. The work of modern superpresses is based on Pascal's law, which allows creating pressures of the order of 800 MPa. Also, this law is the basis for the operation of hydraulic automation systems that control spacecraft, jet airliners, numerically controlled machines, excavators, dump trucks, etc.

Pascal's law is not applicable in the case of a moving liquid (gas), as well as in the case when the liquid (gas) is in a gravitational field; for example, it is known that atmospheric and hydrostatic pressure decreases with height.

Figure 3 - Demonstration of Pascal's law

Consider the most famous device that uses Pascal's law in principle. This is a hydraulic press.

The basis of any hydraulic press are communicating vessels in the form of two cylinders. The diameter of one cylinder is much smaller than the diameter of the other cylinder. The cylinders are filled with liquid, such as oil. From above they are tightly closed by pistons. As can be seen from fig. 4 below, single piston area S 1 many times smaller than the area of the other piston S 2 .

Figure 4 - Communicating vessels

Suppose a force is applied to a small piston F1 . This force will act on the liquid, distributing over the area S1 . The pressure exerted by a small piston on a liquid can be calculated by the formula:

According to Pascal's law, this pressure will be transmitted unchanged to any point in the fluid. This means that the pressure exerted on the large piston p 2 will be the same:

This implies:

Thus , the force acting on the large piston will be so many times greater than the force applied to the small piston, how many times the area of the large piston is greater than the area of the small piston.

As a result, the hydraulic machine allows you to get gain in strength equal to the ratio of the area of the larger piston to the area of the smaller piston.

5. Law of Archimedes. Bodies floating condition

A body immersed in a liquid, in addition to gravity, is affected by a buoyant force - the Archimedes force. The fluid presses on all faces of the body, but the pressure is not the same. After all, the lower face of the body is immersed in the liquid more than the upper, and the pressure increases with depth. That is, the force acting on the lower face of the body will be greater than the force acting on the upper face. Therefore, a force arises that tries to push the body out of the liquid.

The value of the Archimedean force depends on the density of the liquid and the volume of that part of the body that is directly in the liquid. The Archimedes force acts not only in liquids, but also in gases.

Law of Archimedes : a body immersed in a liquid or gas is subjected to a buoyant force equal to the weight of the liquid or gas in the volume of the body.

The Archimedes force acting on a body immersed in a liquid can be calculated by the formula:

where ρ w is the liquid density, V Fri is the volume of the part of the body immersed in the liquid.

Two forces act on a body that is inside a liquid: the force of gravity and the force of Archimedes. Under the influence of these forces, the body can move. There are three conditions for floating bodies (Fig. 5):

if gravity is greater than the Archimedean force, the body will sink, sink to the bottom;
if the force of gravity is equal to the force of Archimedes, then the body can be in equilibrium at any point in the fluid, the body floats inside the fluid;
if the force of gravity is less than the Archimedean force, the body will float, rising up.

Figure 5 - Conditions for floating bodies

Archimedes' principle is also used for aeronautics. The Montgolfier brothers created the first hot air balloon in 1783. In 1852, the Frenchman Giffard created an airship - a controlled balloon with an air rudder and propeller.

6. Hydrostatic paradox

If the same liquid is poured to the same height into vessels of different shapes, but with the same bottom area, then, despite the different weight of the poured liquid, the pressure force on the bottom is the same for all vessels and is equal to the weight of the liquid in the cylindrical vessel.

This phenomenon is calledhydrostatic paradoxand is explained by the property of a liquid to transmit pressure produced on it in all directions.

In vessels of various shapes (Fig. 6), but with the same bottom area and the same liquid level in them, the pressure of the liquid on the bottom will be the same. It can be calculated:

P = p ⋅ S = g ⋅ ρ ⋅ h ⋅ S

S - bottom area

h is the height of the liquid column

Figure 6 - Vessels of various shapes

The force with which the liquid presses on the bottom of the vessel does not depend on the shape of the vessel and is equal to the weight of the vertical column, the base of which is the bottom of the vessel, and the height is the height of the liquid column.

In 1618, Pascal amazed his contemporaries by breaking a barrel with just a mug of water poured into a thin tall tube inserted into the barrel.

7. Hydrodynamics, basic concepts

Hydrodynamics is a section of hydraulics that studies the laws of motion of fluids under the action of applied external forces and their interaction with surfaces.

The state of a moving fluid at each of its points is characterized not only by density and viscosity, but also, most importantly, by the velocity of fluid particles and hydrodynamic pressure.

The main object of study is the fluid flow, which is understood as the movement of a fluid mass bounded in whole or in part by some surface. The bounding surface can be solid (for example, river banks), liquid (interface between states of aggregation), or gaseous.

Fluid flow can be steady and unsteady. Steady-state movement is such a movement of a fluid in which at a given point in the channel the pressure and speed do not change with time

υ = f(x, y, z) and p = f(x, y, z)

Motion, in which the speed and pressure change not only from the coordinates of space, but also from time, is called unsteady or non-stationary υ \u003d f (x, y, z, t) and p \u003d f (x, y, z, t)

An example of a steady motion is the outflow of a liquid from a vessel with a constant level maintained through a conical tube. The speed of the fluid in different sections of the tube will vary, but in each of the sections this speed will be constant, not changing in time.

If, in such an experiment, the liquid level in the vessel is not maintained constant, then the movement of the liquid along the same conical tube will have an unsteady (unsteady) character, since the velocity in the tube sections will not be constant in time (it will decrease with decreasing liquid level in the vessel).

Distinguish between pressure and non-pressure fluid movement. If the walls completely restrict the fluid flow, then the movement of the fluid is called pressure (for example, the movement of fluid through completely filled pipes). If the restriction of the flow by the walls is partial (for example, the movement of water in rivers, canals), then such movement is called non-pressure.

The direction of velocities in the flow is characterized by a streamline.
Streamline - an imaginary curve drawn inside the fluid flow in such a way that the velocities of all particles located on it at a given moment of time are tangent to this curve.

Figure 7 - Current line

The streamline differs from the trajectory in that the latter reflects the path of any one particle over a certain period of time, while the streamline characterizes the direction of movement of a set of fluid particles at a given time. With steady motion, the streamline coincides with the trajectories of motion of fluid particles.

If in the cross section of the fluid flow to select an elementary area∆S and draw a streamline through the points of its contour, then you get the so-called current tube . The fluid inside the current tube formsan elementary trickle. The fluid flow can be considered as a set of all moving elementary jets.

Figure 8 - Current tube

The living section ω (m²) is the cross-sectional area of the flow, perpendicular to the direction of flow. For example, the living section of a pipe is a circle.

Wetted perimeter χ ("chi") - part of the perimeter of the living section, bounded by solid walls (in the figure it is highlighted by a thickened line).

Figure 9 - Living section

Hydraulic flow radius R - the ratio of the open area to the wetted perimeter

The flow rate Q is the volume of liquid V flowing per unit time t through the open area ω.

The average flow velocity υ is the velocity of the liquid, determined by the ratio of the liquid flow rate Q to the open area ω

Since the speed of movement of various particles of a liquid differs from each other, therefore, the speed of movement is averaged. In a round pipe, for example, the velocity on the axis of the pipe is maximum, while at the walls of the pipe it is equal to zero.

Continuity (continuity) equation

The equation of the continuity of flows follows from the law of conservation of matter and the constancy of the flow rate of the liquid throughout the flow. Imagine a pipe with a variable free cross section.

Figure 10 - Demonstration of the jet continuity equation

The fluid flow through the pipe in any of its sections is constant, because the law of conservation of energy is satisfied. We also assume that the fluid is incompressible. So Q 1 = Q 2 = const, whence

ω 1 υ 1 = ω 2 υ 2

Or another way to write this equation is:

Those. average speeds v1 and v2 are inversely proportional to the corresponding areas of living sections w 1 and w 2 fluid flow.

So, the continuity equation expresses the constancy of the volume flow Q , and the condition of fluid jet continuity along the length of the steady fluid flow.

9. Bernoulli's equation for an ideal fluid

Daniel Bernoulli's equation, obtained in 1738, shows the relationship between pressure p, average velocity υ and piezometric height z in various sections of the flow and expresses the law of conservation of energy in a moving fluid.

Consider a pipeline of variable diameter located in space at an angle β (see Fig. 10)

Figure 11 - Demonstration of the Bernoulli equation for an ideal fluid

Let us randomly choose two sections on the pipeline section under consideration: section 1-1 and section 2-2. Up the pipeline from the first section to the second one moves a liquid with a flow rate Q.

To measure the pressure of a liquid, piezometers are used - thin-walled glass tubes in which the liquid rises to a height. In each section, piezometers are installed, in which the liquid level rises to different heights.

In addition to piezometers, in each section 1-1 and 2-2, a tube is installed, the bent end of which is directed towards the fluid flow, which is called the Pitot tube. The liquid in the pitot tubes also rises to different levels as measured from the piezometric line.

The piezometric line can be constructed as follows. If we put several of the same piezometers between sections 1-1 and 2-2 and draw a curve through the readings of the liquid levels in them, we will get a broken line (shown in the figure).

But the height of the levels in Pitot tubes relative to an arbitrary horizontal line 0-0 (the reference plane of coordinates), called the plane of comparison, will be the same.

If a line is drawn through the readings of the liquid levels in the Pitot tubes, then it will be horizontal and will reflect the level of the total energy of the pipeline.

For two arbitrary sections 1-1 and 2-2 of the flow of an ideal fluid, the Bernoulli equation has the following form:

Since sections 1-1 and 2-2 are taken arbitrarily, the resulting equation can be rewritten differently:

The formulation of the equation is as follows:

The sum of the three terms of the Bernoulli equation for any section of the flow of an ideal fluid is a constant value.

From an energy point of view, each term in the equation represents certain types of energy:

z1 and z2 - specific position energies characterizing the potential energy in sections 1-1 and 2-2;- specific pressure energies characterizing the potential energy of pressure in the same sections;- specific kinetic energies in the same sections.

It turns out that the total specific energy of an ideal fluid in any section is constant.

There is also a formulation of the Bernoulli equation from a geometric point of view. Each term of the equation has a linear dimension. z 1 and z 2 - geometric heights of sections 1-1 and 2-2 above the comparison plane;- piezometric heights;- high-speed heights in the specified sections.

In this case, the Bernoulli equation can be read as follows: the sum of the geometric, piezometric and velocity heights for an ideal fluid is a constant.

10. Bernoulli's equation for a real fluid

The Bernoulli equation for the flow of a real fluid is different from the Bernoulli equation for an ideal fluid.

When a real viscous fluid moves, friction forces arise, for example, due to the fact that the surface of the pipeline has a certain roughness, to overcome which the fluid expends energy. As a result, the total specific energy of the liquid in section 1-1 will be greater than the total specific energy in section 2-2 by the value of the lost energy.

Figure 12 - Demonstration of the Bernoulli equation for a real fluid

Lost energy (lost head) are denotedhas a linear dimension.

The Bernoulli equation for a real fluid will look like:

As the fluid moves from section 1-1 to section 2-2, the lost head increases all the time (the lost head is marked with vertical shading).

Thus, the level of initial energy, which the liquid has in the first section, for the second section will be the sum of four components: geometric height, piezometric height, velocity height and lost head between sections 1-1 and 2-2.

In addition, two more coefficients α appeared in the equation 1 and α 2 , which are called Coriolis coefficients and depend on the fluid flow regime (α = 2 for laminar regime, α = 1 for turbulent regime).

Lost Heightconsists of the head loss along the length of the pipeline, caused by the friction force between the layers of the liquid, and the losses caused by local resistances (changes in the flow configuration, for example, a gate valve, a pipe turn)

H lengths + h places

With the help of the Bernoulli equation, most problems of practical hydraulics are solved. To do this, choose two sections along the length of the flow, so that for one of them the values \u200b\u200bof p, ρ are known, and for the other section one or the values \u200b\u200bare to be determined. With two unknowns for the second section, the equation of constancy of fluid flow υ is used 1 ω 1 = υ 2 ω 2 .

11. Questions for self-preparation of students

What forces cause a body to float in water? Explain the conditions under which a body begins to sink.
What do you think is the difference between an ideal liquid and a real one? Does an ideal liquid exist in nature?
What types of hydrostatic pressure do you know?
If we determine the hydrostatic pressure at a point in the liquid at a depth h , then what forces will act on this point? Name and explain your answer.
What physical law underlies the continuity equation and the Bernoulli equation? Explain the answer.
Name and briefly describe the devices, the principle of which is based on Pascal's law.
What is the physical phenomenon called the hydrostatic paradox?
Coriolis coefficient, average flow rate, pressure, head loss along the length of the pipeline .... Explain which equation relates all these quantities, and what is not already indicated in this listing.
Name the formula relating specific gravity and density.
The fluid jet continuity equation plays a rather important role in hydraulics. What kind of liquid is it true for? Explain your answer.
Name the names of all the scientists named in this methodological manual, and briefly explain their discoveries.
Do ideal fluid, streamline, vacuum exist in the world around us? Explain your answer.
Name the devices for measuring various types of pressure according to the scheme: “Type of pressure ... .. - device ... ..”.
Give examples from everyday life, types of pressure and non-pressure movement of a fluid, stationary and unsteady.
For what purposes are piezometers, barometers, and pitot tubes used in practice?
What happens if, when measuring pressure, it is found that it is much higher than the normative values? What if it's less? Explain your answer.
What is the difference between the objects of study of the sections "hydrostatics" and "hydrodynamics"?
Explain the geometric and energetic meaning of the Bernoulli equation?
Wetted perimeter, clear section... Continue this list and explain what the listed terms characterize.
List what laws of hydraulics you learned from this methodological manual, and what physical meaning do they carry?

Conclusion

I hope that this manual will help students to better understand the educational material of the disciplines "Hydraulics", "Fundamentals of Hydraulics, Thermal Engineering and Aerodynamics" and, most importantly, to get an idea of the most "bright" moments of the discipline being studied, i.e. about the fundamental laws of hydraulics. The operation of many devices that we use at work and in everyday life are based on these laws, often without even realizing it.

Sincerely, Markova N.V.

Bibliography

Bryukhanov O.N. Fundamentals of hydraulics and heat engineering: A textbook for students. inst. avg. prof. education / Bryukhanov O.N., Melik-Arakelyan A.T., Korobko V.I. - M.: ITs Academy, 2008. - 240 p.
Bryukhanov O.N. Fundamentals of Hydraulics, Heat Engineering and Aerodynamics: A Textbook for Students. inst. avg. prof. education / Bryukhanov O.N., Melik-Arakelyan A.T., Korobko V.I. - M.: Infra-M, 2014, 253 p.
Gusev A. A. Fundamentals of hydraulics: A textbook for students. inst. avg. prof. education / A. A. Gusev. - M.: Yurayt Publishing House, 2016. - 285 p.
Ukhin B.V. Hydraulics: A textbook for students. inst. avg. prof. education / Ukhin B.V., Gusev A.A. - M.: Infra-M, 2013, 432 p.

MINISTRY OF AGRICULTURE AND FOOD OF THE REPUBLIC OF BELARUS

EE "GORODOKSKY STATE AGRARIAN AND TECHNICAL COLLEGE"

BASICS OF HEAT ENGINEERING AND HYDRAULICS

allowance for students of the correspondence department

in questions and answers

partI

Town

"Reviewed"

at a meeting of the methodological commission

general professional disciplines

Protocol No. ____ dated ________________

Chairman: ________

The manual is intended for students of the correspondence department of specialties 2-74 06 01 "Technical support of agricultural production processes" and 2-74 06 31 "Power supply of agricultural production" for independent study of the discipline "Fundamentals of heat engineering and hydraulics".

Introduction. 5

Fuel and energy complex of the Republic of Belarus. 6

Working body and its parameters.. 11

Basic gas laws.. 12

Basic equations of thermodynamics. fourteen

gas mixtures. Dalton's Law. sixteen

Heat capacity: its types, calculation of heat consumption for heating. eighteen

Heat capacity in processes at constant pressure and at constant volume 19

The first law of thermodynamics and its analytical expression. 21

The concept of a thermodynamic process, their types.. 22

isochoric process. Its graph in - coordinates and basic equations 23

isobaric process. Its plot in - coordinates and basic equations 24

isothermal process. Its plot in - coordinates and basic equations 26

adiabatic process. Its plot in - coordinates and basic equations 28

circular process. Its schedule and efficiency.. 30

Carnot cycle and its efficiency.. 31

Water vapor. Basic definitions. 33

The process of vaporization in - coordinates. 35

The ideal cycle of a steam power plant and its efficiency.. 37

C. Their classification. 40

Ideal cycles for D.V.S. Their efficiency.. 42

Real ICE cycles, power determination. 45

Heat balance and specific fuel consumption in internal combustion engines.. 48

Operation diagram and indicator diagram of a single-stage compressor 49

The indicator diagram of a virtual compressor. 51

Multistage reciprocating compressors.. 53

The concept of the operation of centrifugal, axial and rotary compressors 56

Heat transfer methods. 58

Heat transfer by thermal conduction through a single-layer flat wall 60

Heat conduction through a multilayer wall. 62

Heat conduction through cylindrical walls. 64

convective heat transfer. 66

Heat transfer by radiation.. 67

Heat exchangers. Their types.. 70

Fundamentals of calculation of heat exchangers. 72

Complex heat transfer through a flat wall. 75

Heat transfer through a cylindrical wall. 78

Introduction

The discipline "Fundamentals of Heat Engineering and Hydraulics" provides for the study by students of the basics of thermodynamics and hydraulics, the principles of operation of boilers and drying plants, internal combustion engines, compressors, refrigeration machines, solar water heaters and pumps. The main energy problem facing science is to improve the technical and economic performance of heat engineering and power equipment, which will undoubtedly lead to a reduction in fuel consumption and an increase in efficiency.

Thermal power engineering - the main branch of industry and agriculture, which is engaged in the conversion of natural thermal resources into thermal, mechanical and electrical energy. An integral part of the thermal power industry is technical thermodynamics, which deals with the study of physical phenomena associated with the transformation of heat into work. Based on the laws of thermodynamics, calculations are made for heat engines, heat exchangers. The conditions for the greatest efficiency of power plants are determined. A great contribution to the development of heat engineering was made by those who created the classic works on thermodynamics.

Systematized the laws of convective and radiant heat transfer.

They laid the foundations for the design and construction of steam boilers and engines.

Knowledge of the laws of technical thermodynamics and the ability to apply them in practice makes it possible to improve the operation of heat engines and reduce fuel consumption, which is very important at the present time, when prices for hydrocarbon raw materials are increasing and consumption volumes are increasing.

Question 1

Fuel and energy complex of the Republic of Belarus

The highest priority of the energy policy of the Republic of Belarus, along with the sustainable provision of the country with energy carriers, is the creation of conditions for the functioning and development of the economy with the most efficient use of fuel and energy resources.

Own reserves of fuel and energy resources in the Republic of Belarus are insufficient and amount to approximately 15-20% of the consumed amount. In sufficient quantities there is peat and wood, brown coal, slates are rather low-calorie.

Oil is produced in the Republic of Belarus about 2 million tons per year. Gas about 320-330 thousand tons of fuel equivalent The remaining energy carriers are purchased abroad, mainly from Russia.

The price of energy carriers has seriously increased. So for 1000 m3 of gas 115u. e, oil - for one ton 230 c.u. e. In a year Belarus buys about 22 billion natural gas and about 18 million oil. So that the country's energy security does not depend on one supplier, negotiations are underway with Azerbaijan, the Middle East, Venezuela, which in the future will sell hydrocarbon raw materials in the form of oil.

At present, the government and the energy saving committee put great emphasis on the use of local fuels, and by 2010 they should reduce the consumption of purchased energy resources by 20-25%.

Peat.

More than 9,000 peat deposits have been explored in the republic with a total area within the boundaries of the industrial depth of the deposit of 2.54 million hectares and initial peat reserves of 5.65 billion tons. To date, the remaining geological reserves are estimated at 4.3 billion tons, which is 75% from the original ones.

The main reserves of peat lie in deposits used by agriculture (1.7 billion tons and 39% of the remaining reserves) or attributed to nature protection objects (1.6 billion tons or 37%).

Peat resources included in the developed fund are estimated at 260 million tons, which is 6% of the remaining reserves. The reserves recoverable during the development of deposits are estimated at 110-140 million tons.

Burning shale.

The predicted reserves of oil shale (Lubanskoye and Turovskoye deposits) are estimated at 11 billion tons, industrial - 3 billion tons. t.

The most studied is the Turovskoye deposit, within which the first mine field with reserves of 475-697 million tons was previously explored, 1 million tons of such shale is equivalent to about 220 thousand tons. here. Calorific value - 1000-1500 kcal / kg, ash content -75%, resin yield 6 - 9.2%, sulfur content 2.6%

According to their quality indicators, Belarusian oil shale is not an efficient fuel due to the high ash content and low calorific value. They require preliminary thermal processing with the release of liquid and gaseous fuels. Taking into account the fact that the cost of the products obtained is higher than world prices and oil, as well as taking into account environmental damage due to the emergence of huge ash dumps and the content of carcinogenic substances in the ash. The extraction of shale and the forecast period is inappropriate.

Brown coals.

The total reserves of brown coal is 151.6 million tons

Two deposits of the Zhitkovichskoye field have been explored in detail and prepared for industrial development: Severnaya (23.5 million tons) and Naidinskaya (23.1 million tons), two other deposits (South - 13.8 million tons and Kolmenskaya - 8.6 million tons). .t) explored beforehand.

The use of brown coal is possible in combination with peat in the form of briquettes.

Estimated cost of coal reserves is estimated at 2 tons of fuel equivalent. in year.

Firewood.

In general, in the republic, the annual volume of centralized procurement of firewood and sawmill waste is about 0.94 - 1.00 million tons of fuel equivalent. m. Part of the firewood is supplied to the population through self-procurement, the volume of which is estimated at the level

0.3-0.4 million tons of equivalent fuel

The maximum capacity of the republic for the use of firewood as fuel can be determined based on the natural annual growth of wood, which is approximately estimated at 25 million cubic meters. m or 6.6 mln. tons per year (if you burn everything that grows), including in contaminated areas. Gomel region - 20 thousand cubic meters. m or 5.3 thousand tce To use wood from these areas as fuel, it is necessary to develop and implement gasification technologies and equipment. Taking into account the fact that by 2015 it is planned to double the harvesting of wood for the production of thermal energy, the projected annual volume of wood fuel by 2010 may increase to 1.8 million tons of fuel equivalent.

Renewable energy sources.

The potential capacity of all watercourses in Belarus is 850 MW, including technically available capacity - 520 MW, and economically viable - 250 MW. Due to hydro resources, by 2010 it is possible to generate 40 million kWh and, accordingly, to displace 16 thousand tons of fuel equivalent.

On the territory of the Republic of Belarus, 1840 sites have been identified for the placement of wind turbines with a theoretical potential of 1600 MW and an annual electricity generation of 16 thousand tons of fuel equivalent.

However, in the period up to 2015, the technically possible and economically feasible use of the wind potential will not exceed 5% of the installed capacity e and will amount to 720-840 million kWh.

World reserves of energy carriers.

The theoretical foundations of refrigeration plant and machine processes as well as air conditioning concepts are mainly based on two fundamental sciences: thermodynamics and hydraulics.

Definition 1

Thermodynamics is a science that studies the patterns of transformation of internal energy into various chemical, physical and other processes considered by scientists at the macro level.

Thermodynamic provisions are based on the first and second laws of thermodynamics, which were first formulated at the beginning of the 19th century and became the development of the foundations of the mechanical hypothesis of heat, as well as the law of transformation and conservation of energy, formulated by the great Russian researcher M.V., Lomonosov.

The main direction of thermodynamics is technical thermodynamics, which studies the processes of mutual transformation of heat into work and the conditions under which these phenomena occur most efficiently.

Definition 2

Hydraulics is a science that studies the laws of equilibrium and movement of fluids, as well as developing methods for using them to solve complex engineering problems.

The principles of hydraulics are often used in solving many issues related to the design, engineering, operation and construction of various hydraulic pipelines, structures and machines.

The outstanding founder of hydraulics is the ancient Greek thinker Archimedes, who wrote the scientific work “On Floating Bodies”. Hydraulics as a science arose much earlier than thermodynamics, which is directly related to the social intellectual activity of man.

Development of hydraulics and thermodynamics

Figure 1. Hydraulic flow measurement. Author24 - online exchange of student papers

Hydraulics is a complex theoretical discipline that carefully studies issues related to the mechanical movement of various fluids in natural and man-made conditions. Since all elements are considered as indivisible and continuous physical bodies, hydraulics can be considered one of the sections of continuum mechanics, to which it is customary to include a special substance - liquid.

Already in ancient China and Egypt, people were able to build dams and water mills on rivers, irrigation systems in huge rice fields, in which powerful water-lifting machines were used. Rome, six centuries BC. e. a water pipe was built, which speaks of the ultra-high technical culture of that time. The first treatise on hydraulics should be considered the teachings of Archimedes, who was the first to invent a machine for lifting water, which was later called the “Archimedean screw”. It is this device that is the prototype of modern hydraulic pumps.

The first pneumatic concepts arose much later than hydraulic ones. Only in the XVIII century. n. e. in Germany, a machine for the "movement of gas and air" was introduced. With the development of technology, hydraulic systems were modernized and the scope of their practical application quickly expanded.

In the development of thermodynamics in the 19th century, scientists distinguish three main periods, each of which had its own distinctive properties:

the first one was characterized by the formation of the first and second thermodynamic principles;
the second period lasted until the middle of the 19th century and was distinguished by the scientific works of outstanding European physicists such as the Englishman J. Joule, the German researcher Gottlieb, and W. Thomson;
The third generation of thermodynamics is opened by the famous Austrian scientist and member of the St. Petersburg Academy of Sciences Ludwig Boltzmann, who, through numerous experiments, established the relationship between the mechanical and thermal forms of motion.

Further, the development of thermodynamics did not stand still, but advanced at an accelerated pace. Thus, the American Gibbs developed chemical thermodynamics in 1897, that is, he made physical chemistry an absolutely deductive science.

Basic concepts and methods of two scientific directions

Figure 2. Hydraulic resistance. Author24 - online exchange of student papers

Remark 1

The subject of research in hydraulics is the basic laws of equilibrium and the chaotic movement of fluids, as well as methods for activating hydraulic systems for water supply and irrigation.

All these postulates were known to man long before our era. The term "fluid" in fluid mechanics has a broader meaning than is commonly believed in thermodynamics. The concept of "fluid" includes absolutely all physical bodies that can change their shape under the influence of arbitrarily small forces.

Therefore, this definition means not only ordinary (drop) liquids, as in thermodynamics, but also gases. Despite the difference in the branches of physics under study, the laws of motion of dropping gases and liquids under certain conditions can be considered the same. The main of these conditions is the speed indicator compared to the same sound parameter.

Hydraulics studies primarily the flow of fluids in various channels, that is, flows limited by dense walls. The concept of "channel" includes all devices that restrict the flow itself, including the flow parts of pumps, pipelines, gaps and other elements of hydraulic concepts. Thus, in hydraulics, mainly internal flows are studied, and in thermodynamics, external ones.

Remark 2

The subject of thermodynamic analysis is a system that can be separated from the environment by some control surface.

The research method in thermodynamics is a macroscopic method.

To accurately characterize the macrostructural properties of the system, the values of the macroscopic concept are used:

nature:
temperature;
pressure;
specific volume.

The peculiarity of the thermodynamic method lies in the fact that its base is the only fundamental law of nature - the law of transformation and conservation of energy. This means that all the key relationships that form the basis of the mathematical apparatus are derived only from this position.

Fundamentals of hydraulics and thermodynamics

When studying the basics of hydraulics and thermodynamics, it is necessary to rely on the representations of those sections of physics that will help to better master and understand the principle of the functionality of hydraulic machines.

All physical bodies are made up of atoms that are in constant motion. Such elements attract at a relatively short distance and repel at a fairly close one. At the center of the smallest particle is a positively charged nucleus, around which electrons randomly move, forming electron shells.

Definition 3

A physical quantity is a quantitative description of the properties of a material body, which has its own unit of measurement.

Almost a century and a half ago, the German physicist K. Gauss proved that if you choose independent units of measurement for several parameters, then on their basis, by means of physical laws, it is possible to establish units of quantities included in absolutely any section of physics.

The unit of speed in hydraulics is a derived unit of concept derived from the system units of the meter and second. The considered physical quantities (acceleration, speed, weight) are determined in thermodynamics using the basic units of measurement and have a dimension. Despite the presence of molecular forces, water molecules are always in constant motion. The higher the temperature of a liquid, the faster its constituent parts move.

Let us dwell in more detail on some physical properties of liquids and gases. Liquids and gases in a hydraulic system can easily deform while retaining their original volume. In a thermodynamic system, things look completely different. For such a deformation in thermodynamics, it is not necessary to perform any mechanical work. This means that the elements operating in a certain concept weakly resist a probable shift.