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What´s that and how do they work?>
Improvements in energy efficiency, leading to lower environmental pollution, particularly by CO2, can be achieved in many ways. The heat pump, which can be used for heating and cooling buildings as well as in many industrial processes, offers the best prospects for attaining these goals in a wide variety of appropriate applications.
By upgrading low temperature heat, enabling it to be used at a higher temperature, the heat pump can use fossil fuel resources more effectively than conventional heating methods.
The heat pump is the only known process that recirculates environmental or waste heat back into a heat production process, and therefore can dramatically reduce the demand for fossil fuels as well as NOx, hydrocarbons, acid rain and CO2-emissions.
Detailed studies have shown that electric- or gas-driven heat pumps would reduce emissions of CO2 and other pollutants associated with space heating in Europe by between 30 % and 50 %, depending upon the conditions of use.
The vast majority of heat pumps operate on the vapour compression cycle , which can accommodate electric motor or gas engine drives. A growing minority of heat pumps employ what is called the absorption cycle. They predominantly use gas as fuel and are directly-fired. Many other methods exist, but are not yet widely applied.
Source: Brochure \"Heat Pumps - an option for an energy efficient and clean society\" of the Commission of the European Communities.
The vapour compression cycle is used in the majority of heat pumps, and the use of electric motor drives dominates such units. The principal components in the basic vapour compression cycle circuit are shown in the figures opposite. These comprise an evaporator and condenser, the compressor and its drive and an expansion valve. Not to be omitted is the working fluid, or refrigerant, which circulates around the system.
The fluid is evaporated at low temperature and pressure in the evaporator, using heat from the heat source. The vapour is then compressed, raising its temperature before proceeding to the condenser, which gives out useful heat by condensing the working fluid at this higher temperature. The flow of the fluid through the expansion valve reduces the pressure to that of the level in the evaporator.
The net heat output at the condenser is effctively the sum of that taken in at the evaporator, and the heat equivalent of the work of compression put in by the drive. This leads to an energy \"bonus\" which sets the heat pump apart from other heating methods - the heat delivered is greater than that which could result from fully effective use of the primary energy alone.
In the case of a gas engine drive heat may be recovered from the water jacket and exhaust to supplement that delivered at the condenser.
The absorpotion cycle is not expainded by me, because it would exceed our time.
How are heat pumps judged?
When you buy an automobile, you ask for the power.
Heat pumps are judges by there performance number, this number is usually bigger than 1 and means, e.g. with a number from 3, that 1 Wh electrical energy supplies the water an energy of 3 Wh. An direct heater work with an performance number from maximal 1, because they don´t use the environment heat.
Why is there a compressor in use?
The reason for using a compressor is that the refrigerant energy output becomes bigger because of the higher pressure. This circumstance is the same as it is with water. That means that the refrigerant is able to give more energy to the used medium.
Importent is that the refrigerant is converted to low pressure as it is at the evaporator, after the condenser again, otherways you will have a problem with the huge losses.
If you want to see an heat pump modell, you should go to the mechanical installations in our school.
Placement in real life:
Vocabulary:
heat pump Wärmepumpe
environment Umgebung
prospect Aussicht
to attain erreichen, erzielen
appropriate geeignet
associate kombinieren
the vast majority große Mehrheit, enorme Mehrheit
accommodate hier: unterbringen, beinhalten
minority Minderheit
expansion valve, throttl valve Expansionsventil
not to be omitted nicht zu (verabsäumen, vernachläßigen) ist
performance number Leistungsziffer, Arbeitszahl
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