The absorption heat pumps: definition, principles of operation, types, advantages and disadvantages
The heat pump is an apparatus capable of transferring the heat present in a fluid at a lower temperature to another fluid at a higher temperature.
The heat pump must therefore its name to the fact that it provides to raise the heat from a lower level to a higher level of temperature, thus reversing the natural flow of heat that in nature, however, flows from a higher temperature level to a lower one.
Currently, commercially available are two different types of heat pumps:
- Electrical, operating by means of an electrically powered compressor;
- Absorption, operating by means of a burner fed with methane or LPG.
Let us now analyze, in particular, the features and benefits, in terms of eco-friendliness, the heat pump absorption.
As the normal boilers used for heating domestic environments, the absorption heat pumps are able to provide both hot water for heating and sanitary (ie the hot water used in the bathroom and kitchen), up to a maximum temperature of 70 degrees, both cold water for summer air conditioning, up to 3 degrees, using the same traditional hydraulic pipes which distribute the hot water.
Since then in part of a condensing boiler and in part of a heat pump, are added so the heat produced by the combustion of the gas to the one retrieved from the external environment, resulting in a significantly more efficient synthesis of the advantages offered individually by the two forms of the most common heating (condensing boiler and electric heat pump).
The advantage of using a heat pump absorption thus derives from its ability to provide more energy than was used for its operation, since it is able to recover the heat from the outside, out of the assets of renewable energy potential contained in the so-called 'cold sources', ie the external means by which you can extract the heat:
- The air, through pumps aerothermal: the air, as the source, has the advantage of being available everywhere but the power delivered by the heat pump decreases with the lowering of its temperature.
- The water (groundwater, river or lake, if present in the vicinity of the premises to be heated and reduced depth) through hydrothermal pumps: water guarantees the performance of the pump without suffering the outside weather conditions, but it requires a cost due to the additional supply system and its treatment.
- The soil, through geothermal pumps: as cold source, has the advantage of being subjected to minor changes in temperature than the air and its heat is absorbed by means of geothermal probes, consisting of special piping, or horizontal (requiring an extension of land equal to about 2 times the surface area to be heated and are buried at a maximum depth of 1/1, 5 meters to not be affected too much of changes in outside air temperature and to maintain the beneficial effects of insolation) or vertical ( several meters long, does not require large extensions, such as the horizontal ones, but the drilling of deep wells in which they can be inserted).
The fluid, air or water that, when one gives the heat produced and recovered from the outside instead it says 'heat sink'. The transfer of heat to the air can occur through:
- Fan, ie structures cabinet in which the air circulates through radiators;
- Funnels, ie nozzles spread that transfer the hot air in the different local.
The transfer of heat to the water, however, can occur through:
- The heating coils with a floor (low temperature system);
- The installation of conventional radiators (plant at high temperature).
The thermal performance of the heat pump varies depending on the temperature of the cold source and the heat sink: more these values differ from each other, the more the thermal efficiency decreases and vice versa. E 'therefore essential to assess the correct sizing of the system, depending on the type of building and use, so that the cost of installation, certainly not insignificant, does not outweigh the benefits in terms of energy savings: the proven reliability of this type of systems, alternative to traditional, can really ensure significant benefits in the reduction of energy consumption, resulting in a positive impact on the environment.
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