What is a mechanical refrigeration system?
A mechanical refrigeration system is a cooling loop with a compressor, condenser, evaporator and expansion valve as main parts. It is a system that moves thermal energy (heat) from one place (where you do not want it) to another place (where you can drop it). A chiller for example subtracts heat from water and moves it to the outside air.Cooling is negative heating
This means that the same chiller moves cold from outside to the water to reduce the water in temperature. But you can also say that is heating the ambient air by subtracting heat from the water.The difference
These units are almost identical, it is the way how they are used. The chiller is primarily used for cooling with heat as waste while the heat pump is used for heating with cold as a rest product. Although the main parts of a heat pump and cooling system are the same, the design and controls are specific for the purpose of heating or cooling.Reversible
Small heat pumps are usually reversible. This means the refrigerant flow can be reversed, so the unit can function as a heater and be used for cooling. Very practical for domestic use: in winter it is a heater and during summer the use is for cooling. One unit with two functions.
Design limitations
In general the lower the temperature difference between the evaporator and the condenser, the more efficient the cycle is. Temperature limitations on the condenser (high-temperature side) mainly depend on the used refrigerant. A maximum temperature of 55 °C is normal but special units may go up to 70°C, but at the cost of high compressor power input.Modern heat pumps
Heat pumps have been available for decades. However, due to the impact of CO2 emissions from fossil fuels on climate change, there is now a booming interest in this technology. Heat pump units are a logical and modern solution for providing air or fluid at moderate temperatures. When powered by green electricity, their operation is climate neutral. Implementing heat pumps requires a fresh perspective on system design, presenting an exciting challenge for engineers.
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