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Small heat pumps for ventilated houses and domestic hot water production.

Author(s) : PAUL J., SANTOS J. P. G. V.

Summary

The increase of the building codes and regulations concerning the energy use has led to the so-called low energy houses. In these modern well insulated and airtight houses, ventilation is mandatory, however, the exhaust air from the ventilation system has the potential to become an excellent heat source for a heat pump. The performance characteristics of heat pump systems are affected by the temperature lift between the cold and warm side, and small temperature lifts are favourable. Using a heat source such as the exhaust air that yields a constant temperature of some 20°C is beneficial. The heat from the exhaust air can be used as heat source by a heat pump to produce both air heating and water heating. Whereas the energy demand in such low energy houses has been heavily reduced over the time, the warm water demand has remained constant. Therefore the portion of energy used for producing domestic hot water in relation to the heating demand of such houses has drastically increased. Due to the odd Legionella problem the hot water temperature must be high, which implies a high condensing temperature and a low COP. The paper describes a method to produce hot water at 55°C with a condensing temperature of only 43°C by employing a suction gas heat exchanger and a refrigerant (R1270, propylene), which has a high superheat enthalpy and a high discharge temperature at the same time. Thus a COP of 3,11 for water heating and a COP of 3,46 for air heating can be achieved for a fully ventilated building at an ambient temperature of 5°C, which is quite good for a small heat pump with a heating capacity of some 2 kW. The heat pump is operated in the "bivalent" mode.

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Pages: 2008-2

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Details

  • Original title: Small heat pumps for ventilated houses and domestic hot water production.
  • Record ID : 2009-0396
  • Languages: English
  • Source: 8th IIR-Gustav Lorentzen Conference on Natural Working Fluids (GL2008)
  • Publication date: 2008/09/07

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