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Evaluation of different evaporator concepts for thermally driven sorption heat pumps and chillers.

Author(s) : SCHNABEL L., WITTE K. T., KOWOL J., et al.

Summary

The ongoing development on more efficient thermally driven adsorption heat pump or chiller shows a strengthened need for improved evaporator concepts. Most of the market available adsorption systems use water as refrigerant, leading to an evaporation need in a temperature range between 3 to 20°C and a pressure range between 7.6 to 23.4 mbar respectively. Even though there is extensive literature on evaporation of water, data on water evaporation at low pressure conditions are still scarce. To close this gap research activities are carried out at Fraunhofer ISE within this field since a few years. The central requirements for the design of an evaporator are a high evaporation rate, low temperature differences between the cold water stream and the evaporating fluid and low pressure drops on the cold water side. These aspects can be evaluated at the evaporation test rig for various heat exchanger designs and operation conditions. This manuscript opposes experimental results of tube bundle heat exchangers (copper) with different kinds of microscopic and macroscopic surface structures. The central aspects of the evaluation are the operation mode (sprinkled versus partially flooded), the filling level for the partially flooded mode and the pressure drop. Smoothed tubes will be used as reference. First results on surface structured tubes showed the potential of increasing the evaporation rate using turbulence inducers. To evaluate those enhancements in a more application-orientated way eye is focused on the pressure drop in relation to the evaporation rate.

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Pages: 543-552

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Details

  • Original title: Evaluation of different evaporator concepts for thermally driven sorption heat pumps and chillers.
  • Record ID : 30001252
  • Languages: English
  • Source: Sources/sinks Alternative to the Outside Air for Heat Pump and Air-conditioning Techniques (Alternative Sources - AS), Padua, Italy, April 5-7, 2011. / International Sorption Heat Pump Conference (ISHPC11), Padua, Italy, April 6-8, 2011.
  • Publication date: 2011/04/06

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