The principle of operation of the heat pump


IMG_22062015_162214Schematically, the heat pump can be represented as a system of three loops: the first, external, circulated teplootdatchik (heat transfer fluid that collects heat environment), the second – the refrigerant (a substance that evaporates, taking heat teplootdatchika, and condensed, giving heat heat sink) in the third – the heat sink (water heating and hot water supply of the building).

The outer loop (the collector) is laid in the ground or water (eg. Polyethylene) pipe, which circulates antifreeze – antifreeze. The source of low potential heat can serve as a ground, rock, lake, river, sea and even the output of warm air from the ventilation system of an industrial enterprise.

In the second loop, where the refrigerant circulates, as in household refrigerators, integrated heat exchangers – the evaporator and condenser, as well as devices that change the pressure of refrigerant – spraying it into the liquid phase reactor (narrow orifice) and compresses it in the gaseous state compressor.

Duty cycle is as follows. The liquid coolant is forced through the throttle, its pressure drops and it enters the evaporator, where the effervescence by the heat energy supplied by the collector of the environment. The gas, which has become the refrigerant sucked into the compressor, compressed and heated, is pushed into the condenser. The condenser is a heat-unit heat pump: heat is taken water in the heating circuit. When the gas is cooled and condensed to once again undergo a discharged in the expansion valve and back to the evaporator. After that, the duty cycle begins again.

To the compressor work (to maintain high pressure and circulation), it must be connected to electricity. But on each spent kilowatt hour of electricity the heat pump produces 2.5-5 kWh of thermal energy. The ratio of generated thermal energy and electrical consumption is called transformation coefficient (conversion coefficient or heat) and is indicative of the efficiency of the heat pump. This value depends on the difference in temperature level in the evaporator and condenser: the greater the difference, the smaller this value.

For this reason, the heat pump is to use as large as possible number of low-potential heat source, rather than attempting to achieve its strong cooling. In fact, while increasing the efficiency of the heat pump, since the weak cooling of the heat source is no significant difference in growth temperature. For this reason, heat pumps are made so that the mass of low-temperature heat source was much greater than the mass heated. This is one of the most important differences from traditional heat pump (fuel) sources of heat, which generated energy depends solely on the calorific value of the fuel. For this reason, a heat pump in a sense, “bound” to the low-potential heat source having a large mass. This problem can be solved by the introduction into the heat pump system of mass transfer, such as water pumping system. That’s the way the central heating system in Stockholm.

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