exchange rate Consumers and sources of heat production

Contents

Introduction

1 Diagrams and equipment of heat stations

1.1 Requirements for thermal points

1.2 Types of thermal points their characteristics

1.3 Heat station equipment

1.4 Consumer Thermal Power Supply Systems

14.1 Hot Water Supply System

1.4.2 Heating system

1.4.3 Air heating and ventilation system

1.5 Schematic diagrams of thermal points

2 Heat engineering calculation of recuperative heat exchanger

2.1 Initial data for recuperative calculation

heat exchanger

2.2 Recuperator Design Calculation

2.2.1 Estimate of heat exchange surface area and

sections for coolant movement

2.2.2 Definition of cross-sectional geometry

heat exchanger

2.2.3 Calculation of heat transfer coefficient and

heat exchange surface area

2.3 Heat Exchanger Span Calculation

Conclusion

List of used literature

Appendix 1 Initial data for recuperator calculation

Annex 2 Thermophysical properties of water at atmospheric pressure

Appendix 3 Recommended coolant rates

Appendix 4 Technical data of section heat exchangers

Appendix 5 Cross-sectional drawing of developed recuperator

Appendix 6 Longitudinal section drawing of developed recuperator

Introduction

Thermal energy is the most important component of a person's vital activity and a necessary condition for improving his living conditions. Reliability and cost-effectiveness of thermal power supply systems depends on rational operation of heat-generating plants, a properly designed thermal circuit, a heat energy producer, heat energy transfer facilities (heat network) and heat consumption systems, wide application of energy-saving technologies and unconventional heat-generating power plants using alternative energy sources, saving thermal energy. Energy saving and optimization of thermal energy production and distribution, adjustment of water and energy balances allow increasing the rate of development of thermal power engineering, improving technical and economic indicators of equipment of heat-generating plants.

For the rational use of thermal energy, its proper distribution both centrally and within an individual consumer plays an important role.

An important role in the rational use of thermal energy is the correct selection of heat exchange devices used in the transfer of thermal energy from one coolant to another. In this case, it becomes necessary not only to select the heat exchanger, but also its structural and span calculation, to determine the main dimensions of such a heat exchanger.

For control of heat consumption modes, transformation and regulation of coolant parameters, as well as for ensuring operability of elements of heat plants and employees for connection of these plants to the heat network and ensuring their operability, a heat station is used.

The correct arrangement of the heat station, maintaining its elements in working condition and optimal adjustment of the mode of operation of the heat station allows significantly reducing the cost of thermal energy for heating and heating water for hot water supply (HVA) needs, improving the room microclimate, reducing capital costs for laying heat networks, etc. This in turn increases the energy efficiency of production, reduces the cost of production and generally contributes to the achievement of the task of energy saving at the state level. In the end, all of the above allows for a relatively simple way to significantly reduce the costs of budgets at all levels, contain the increase in tariffs for thermal energy, increase the competitiveness of individual enterprises and the whole economy as a whole, and increase supply in the labor market.

The purpose of this course work is to study heat points and solve the technical problem of selecting and calculating a heat exchanger.

Diagrams and equipment of heat stations

1.1 Requirements for thermal points.

The thermal station is a complex of devices located in a separate room and consisting of elements of thermal power plants that provide connection of these plants to the thermal network, their operability, control of heat consumption modes, transformation, regulation of coolant parameters/

Heat points are divided into individual (ITP) and central (CTP) heat points.

Heat stations house equipment, instrumentation (hereinafter referred to as instrumentation), control and automation devices with the help of which:

1. Conversion of coolant type and (or) change of its parameters ;

2. Monitoring of coolant parameters;

3 Accounting of heat energy, coolant consumption;

4. Control of coolant flow rate and its distribution;

5. Protection against emergency increase of coolant parameters;

6. Filling and makeup of heat consumption systems;

7. Condensate collection, cooling, return and quality control;

8. Accumulation of thermal energy;

9 Water treatment for hot water supply systems.

All or part of the above functions can be implemented in the heat point. The choice of which functions will be implemented depends on what task this thermal point performs, what connection schemes are used for this particular thermal point, what coolant is used, and what initial costs the organization is ready to incur during the design and installation of the thermal point. However, in any case, heat stations must meet the technical requirements set forth by regulatory documents: technical operation rules for thermal power plants, SP 60.13330.2012 Heating, ventilation and air conditioning and several others.

Main requirements for thermal points:

- connection of heat points to the heat source, as well as distribution of thermal energy and specific scheme of connection of the heat point should ensure the most rational and economical use of heat, including minimization of coolant consumption;

- shut-off valves must be installed in the heat stations, separating the heat station from the heat source and shut-off valves on each branch to the heat consumers;

- air vents and drains shall be installed in the heat station to discharge air from the upper points and drain water and (or) steam condensate from the lower points;

- equipment for mechanical cleaning of suspended coolant particles (mains water) shall be installed at the inlet to the heat station, as well as in front of the control devices and metering devices. Such equipment is mainly filters of various types or mud machines;

- in thermal points it is not allowed to install jumpers between direct and return pipelines, as well as bypass lines around elevators, control valves, filters, thermal energy meters;

- thermal units shall be provided with the possibility of connection of systems for washing the heat point with its subsequent emptying (shut-off valves, connectors, pipes for compressed air supply, etc.). In normal operation, the heating station flushing line shall be disconnected and disconnected.

- connection of all drains to sewage shall be made with visible break..

1.2 Types of thermal points their characteristics

The type of heat station depends on what function it should provide, the number of supply systems, the number of heat consumers, the methods of placement and installation.

Heat points are of the following types:

- individual (hereinafter referred to as ITP);

- central (hereinafter referred to as CTP);

- unit ones (hereinafter referred to as FTP).

ITPs serve one consumer of thermal energy, most often small (up to 50 kW), although in some cases the ITP power can reach 2MW. The main task of ITP is to provide the consumer with heating and hot water. Usually, IT is placed in the basements or technical room, less often in a separate building. Heat carrier and tap water are supplied to ITR. The degree of automation of ITP depends on the tasks solved by the heat point, coolant parameters, the presence of maintenance personnel, etc. For example, throttle washers and pressure controllers and circulation pumps can be used to improve heat efficiency and temperature schedule. In the first case, it will be necessary to carry out thermal and hydraulic calculations of the thermal network, attract third-party organizations and still the result will be only approximate and when the coolant parameters change at the inlet to the ITP, there will be a violation of the heat supply mode of the building, which will not be so easy to restore. In the second case, despite the additional initial costs, the heat supply of the building will be much more reliable and will not require additional maintenance costs.

ITR consists of two circuits:

- the first is a heating circuit for maintaining a predetermined temperature in the heated room;

- secondary circuit is hot water supply circuit.

TSPs are used to provide heat to a group of buildings. CTP perform the function of providing consumers with hot and cold water supply and heat. The degree of automation of central heat stations is determined by the customer and technological needs. TSPs can use both a dependent and independent circuit for connecting to the thermal network. In a dependent scheme, the coolant is divided into a heating system and a WAN system within the heat point itself. In case of independent circuit the coolant is heated in the heat exchanger in the secondary circuit of the heat point by the incoming water from the heat network

Equipment of the central heat station (CTP) consists of the following elements:

1. Heaters (heat exchangers, recuperators) - sectional, multi-pass, block type, plate - depending on the design, for hot water supply, maintaining the required temperature and water head at the water separation points;

2. Circulating utility, fire, heating and standby pumps;

3. Mixing devices;

4. Thermal and water metering units;

5. Instrumentation and automation instrumentation;

6. Shut-off control valves;

7. Expansion membrane tank.

FTP has a block version. FTP may consist of one or more units mounted on one frame. Each module is a separate, independent and complete unit. However, regulation of the operation of such modules is general. FTUs can have both local control and regulation, and remote control.

FTUs can be used as both individual and central heat points.

To temporarily supply the consumer with thermal energy, a modular thermal station is also used, which is a mobile complex of devices for the temporary operation of the heating and hot water supply system. The modular heat station is delivered to the desired place by means of automobile or other mode of transport, and after use, it is returned for its intended purpose.

Heating stations and heating systems can be connected to central heating systems in a dependent and independent scheme. In a dependent scheme, network water is directly supplied to the heating system through the equipment of the heating station. In an independent scheme, network water from the main network is used to heat (in the heat exchanger) the internal heating system, which is supplied by pumps to the needs of the consumer.

1.4.2 Heating system

Heating system is a closed system of pipelines through which coolant is supplied to heating devices.

Depending on the type of connection of heating devices, there are heating systems: single-tube and double-tube.

Single tube systems are characterized by the fact that heating devices are connected in series. At the same time, each subsequent heating device will have a temperature lower than the previous one, which is a very serious drawback of such a system. It is possible to partially compensate for this disadvantage by increasing the heat transfer surface of each subsequent radiator or by increasing the speed of the coolant. Nevertheless, with a single-tube system, very high pipe savings are achieved, which has caused these systems to be quite common, especially in buildings with high storeys.

Two-pipe system consists of supply and return pipeline and each heating device is connected to supply pipeline, and cooled water is discharged through return pipeline.

Depending on the method of laying pipelines, heating systems are with upper wiring and lower wiring. In upper wiring systems, supply pipelines are located above heating devices, and in lower wiring systems, supply and return pipelines are located below heating devices.

Heating systems are available with vertical (if radiators are connected to vertically laid risers) and horizontal (if radiators are connected to horizontally laid risers) heating risers wiring. In systems with vertical wiring, it is necessary to provide for air removal from the upper sections of the thermal network

Heating systems are divided depending on direction of coolant movement into dead end (if coolant in supply and return pipelines moves towards each other) and with associated coolant movement.

The operation of heating systems, their types, methods of connecting heating devices must be known and taken into account during thermal and hydraulic calculations of heat networks, the choice of control valves, heat engineering calculation of the heat exchanger, the selection of its type and connection method.

1.4.3 Air heating and ventilation system

The air heating and ventilation system shall provide the design air exchange of the room and the specified indoor air temperature in accordance with the ambient air temperature and the design coolant temperature.

The main requirements for air heating and ventilation systems are given in the "Rules for technical operation of thermal power plants."

The air heating and ventilation system consists of the following parts

- air ducts, track system along which heated air is supplied to heated rooms;

- power plants (fans) provide movement of specified air volumes;

- control and automation system (a set of sensors, actuators that automate the processes of heating and air supply)

- air preparation unit (required for air filtration, heating, humidification)

The power of the air heating system heaters shall be calculated so that the heat received is sufficient to compensate for all heat losses in the room (through the external walls, through the ventilation system, through the floors and roof). Calorifers connected to steam heat networks are usually connected in parallel, and connected to water heat networks in series.

Heat engineering calculation of recuperative heat exchanger

2.1. Initial data for recuperative heat exchanger calculation

Initial data for recuperative heat exchanger calculation (Appendix 1) are taken according to variant No. 6:

Heating coolant - water;

Heated heat carrier - water;

Heating coolant temperature at the heat exchanger inlet;

Heating coolant temperature at the heat exchanger outlet;

Mass flow rate of heated coolant;

Temperature of heated heat carrier at the heat exchanger inlet;

Temperature of heated heat carrier at the heat exchanger outlet;

Required:

Develop a recuperator design that meets the initial requirements;

Perform structural calculation of the recuperator with determination of its main geometric dimensions;

Perform recuperator check calculation.

Conclusion

Thus, having considered various options and schemes for the use of thermal energy for domestic and industrial purposes, we can use the acquired knowledge for rational design and installation of thermal points of any purpose. The considered examples of heat points, heating, ventilation systems, existing and promising equipment of the heat point, allows us to acquire initial data on this type of equipment, on the principles of their selection and rational use

The above heat exchanger design calculation procedure gives an idea of the prerequisites and sequence of determining the main geometric dimensions of the recuperator corresponding to the initial design data. The given structural calculation of the heat exchanger showed the practical possibility of applying the acquired knowledge in the field of design and installation of heat exchangers

The considered method of test calculation of the heat exchanger allows to determine the temperatures of heating and heated heat carriers at the outlet of the recuperator, if their flow rates and initial temperatures are known, as well as the main geometric dimensions of the heat exchanger. This significantly reduces the costs of selecting and installing heat exchangers of all types, reduces the installation and adjustment time of these heat exchangers, which will ultimately have a positive impact on the competitiveness of the enterprise, on improving the energy efficiency of both the individual enterprise and the whole country.