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Analysis of the part load behaviour of sorption chillers with thermally driven solution pumps.

Author(s) : ALBERS J., ZIEGLER F.

Summary

It is well known that thermally driven solution pumps (thermosiphon generators) can be used in absorption refrigeration cycles. This kind of solution pump has some advantages over the mechanical pumping principle: the processes of refrigerant generation and solution pumping are combined in one hermetic unit, the costs for maintaining the vacuum are decreased, and a moving part is eliminated from the system. When analysing the part-load characteristics of commercial H2O/LiBr-absorption chillers with thermally driven solution pumps, a considerable (and negative) deviation is found as compared to systems using mechanical pumps. This deviation is characterized by a rapidly decreasing COP at low chilled water temperatures. On the other hand, at high chilled water temperatures the cooling capacity does not increase as expected. This specific part-load behaviour is due to the kind of evaporator used, and to the performance of the thermally driven solution pump. The paper reports about measurements, recorded using a commercial H2O/LiBr-absorption chiller with thermally driven solution pump in a solar cooling application. These results are compared with theoretically expected data using the method of characteristic temperature differences. It was shown that the rich solution mass flow rate is strongly influenced by the temperature difference of hot and cooling water, which is also known as the temperature thrust. It follows that especially for optimizing solar cooling systems it is necessary to control both temperatures individually.

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Details

  • Original title: Analysis of the part load behaviour of sorption chillers with thermally driven solution pumps.
  • Record ID : 2005-0156
  • Languages: English
  • Source: 21st IIR International Congress of Refrigeration: Serving the Needs of Mankind.
  • Publication date: 2003/08/17

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