New Stiebel Eltron Guide to heat pumps 
(10/01/2007)
Modern heat pumps save energy and reduce emissions. Heat is a basic human need. When considering heating, many people today think not only of economy, but also of the environment. The development of heat pumps has proven that you can certainly combine the two to excellent effect. Heat pumps utilise energy that is always available in the air, in water and underground and convert that energy into available heat. What is good about this method of yielding heat is that you can always obtain it without damaging the environment. The heat pump is regulated subject to the outside temperature.
What is good about this method of yielding heat is that you can always obtain it without damaging the environment. The heat pump is regulated subject to the outside temperature.
This control unit safeguards the selected set temperature. As a result, the heat pump achieves an excellent ration of “harvested” heat to the expended primary energy. To put it into figures: Each kWh electrical energy spent generates up to 5 kWh available energy, subject to the respective heat source, i.e. from the air, from the groundwater and the ground of your own property.
The compact design requires little space and ensures an easy installation. The lowest installation effort secures the air/water heat pump the top prize for easy installation. With installation internally or externally, it can yield heat for domestic heating from outside air down to a temperature of -20 °C. Future purchasing decisions will increasingly favour products with sound environmental credentials.
Heat pumps from STIEBEL ELTRON already enable the basic premise of heating an apartment or entire houses with environmentally responsible and cost-effective methods to be achieved.
How does a heat pump work?
Heat pump principle
The most important contribution to the heat pump function is made by the refrigerant (in the following the “process medium”). This evaporates at low temperatures. If you route outside air or water to a heat exchanger (evaporator), in which the process medium circulates, then that refrigerant extracts the required evaporation heat from the heat source and changes from the liquid into the gaseous state. During this process, the heat source cools down by a few degrees.
A compressor draws the process medium in and compresses it. The increase in pressure also raises the temperature, in other words, the process medium is “pumped” to a higher temperature level. That requires electrical energy. As the compressor is of the suction gas-cooled design, this energy (motor heat) is not lost, but reaches the downstream condenser together with the compressed process medium. Here, the process medium transfers its absorbed energy to the circulating system of the hot water heating system by being returned into the liquid state again. An expansion valve reduces the still prevalent pressure and the circular process starts again.
Heat pump coefficient of performance
The coefficient of performance eHP is equal to the quotient of heating output QHP and electrical power consumption PHP in accordance with the following equation: eHP = QHP / PHP
It provides a factor, by which the yield is greater than the expenditure. The coefficient of performance is subject to the temperature of the heat source and that of the heat consumer. The higher the heat source temperature and the lower the heat consumer temperature, the higher the coefficient of performance. It relates, as current value, always to a specific operating condition.
Read part 2 of this article: Energy sources for heat pumps
Related categories: Heating, ventilation, refrigeration
