Heat pumps for heating and hot water supply. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Heat pumps for heating and hot water supply. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

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A heat pump is a machine that allows transfer from a less heated body (environment) to a hotter one, due to the expenditure of mechanical energy. The processes occurring in heat pumps are the reverse of the processes carried out by the working fluid in the refrigeration machine. The limiting theoretical cycle of a heat pump is the reverse Carnot cycle.

Heat pumps are non-traditional renewable, environmentally friendly, economical energy sources and are designed to generate thermal energy used for heating and hot water supply for various facilities. During their operation, heat pumps use solar energy accumulated by the earth (ground water), as well as geothermal energy. In addition, heat pumps can be used to utilize the thermal energy of wastewater from cities, industrial facilities and treatment facilities. High energy conversion ratio (η>3.0) opens up broad prospects for the use of these settings.

According to the forecasts of the World Energy Council (WEC), from which it follows that by 2020, 75 percent of the public heating supply in developed countries will be provided by heat pumps. This forecast is justified by the practical organization of heat supply in a number of countries: for example, heat-pumped public heat supply in Sweden is about 50 percent, and in the USA it is close to 37 percent.

Russia has lagged far behind in the development of heat pump technology, and now it is necessary to make great efforts in this area. Heat production using HP is more profitable in Russia compared to all developed countries, primarily due to harsh climatic conditions.

Technically, a heat pump ("Freon boiler") is an installation that transfers heat from a low-temperature heat source to a high-temperature consumer (heating system) through an intermediary.

Any refrigeration unit works according to the same process. The source of heat will be any heat dissipated in nature or technogenic heat.

In the first case, as a rule, these are groundwater, thermal springs or non-freezing reservoirs, in the second - the heat of a cooling tower, ventilation emissions, industrial discharges, treatment facilities, etc. with a temperature of +5 to +40°C, which cannot be directly used for heating and hot water.

The efficiency of the HP is determined by the temperature of the source and is significantly higher than any type of boiler, and even more so electric heaters. Depending on the temperature, a source with 1 kW of consumed electricity HP allows you to issue from 3 to 7 kW of thermal power to the heating system, while the missing 2-6 kW are "taken" from the source. The payback period of HP, depending on the source temperature and the configuration of the installation, can be from several months to two years. HPs do not produce emissions into the atmosphere, thus being environmentally friendly installations compared to boilers.

Currently, the production and implementation of HP in Russia is concentrated mainly in two joint-stock companies, both located in Novosibirsk. These are CJSC Energia, which produces vapor-compression HPs with a capacity of 10 kW to 9 MW, both electric and driven by internal combustion engines and utilizes exhaust heat in HPs, and CJSC Teplosib, which develops absorption lithium bromide HPs with a unit thermal capacity of 25 kW or more. up to 5-10 MW.

Heat pumps manufactured by CJSC "Istochnik", compression type, single-stage, automated, with adjustable heat output, are designed to generate heat and energy (Fig. 8.1).

Heat pumps for heating and hot water supply
Fig.8.1. Heat pump diagram

Principle of operation based on the transformation (transfer) of heat from low-temperature environmental heat sources to a high-temperature heat consumer due to phase transformations of working substances (ozone-friendly freons K 22, K 134, K 142.)

appointment

Heat pumps are used:

for autonomous heat and hot water supply, as well as air conditioning and cooling of industrial and civil facilities;
for drying wood and cereals;
for heating water in swimming pools and fish farms;
for cooling and maintaining a constant water temperature of technological cycles, which will allow the replacement of polluting cooling towers.

Features

Main technical characteristics:

Heat output: 3 - 10 kW;
Average hourly electricity consumption: 0,86 - 2 kWh.

The HP is an exceptionally energy-efficient installation, it saves 268 kg of coal, 84 kg of fuel oil, 58 cubic meters. m of gas for each produced Gcal of heat.

Heat pumps operate fully automatically. The payback period for capital expenditures compared to electric boilers is 1 year, coal - 1 year, oil-fired boilers - 2-3 years. Table 8.1 gives the characteristics of heat pumps.

Table 8.1. Price and characteristics of heat pumps

(click to enlarge)

The power consumption from the mains and the heat output are given at temperatures:

heat source - +8°C;
heat supply - (58-43)°C.

When the temperature of the heat source increases above 80C, the price of kW output power decreases.

The system allows you to generate both electricity and heat at the same time.

HP service life before overhaul:

45000 hours for HP with reciprocating compressor;
60000 hours for HP with screw compressor.

Author: Magomedov A.M.

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