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On the deviation from equilibrium state and the heat and mass transfer capabilities of ionic liquids in absorption chillers.

Number: 0497

Author(s) : KÜHN R.

Summary

In this paper the heat and mass transfer characteristics of different ionic liquids, investigated in an experimental absorption chiller, are discussed. The vessels are made of glass and copper tube-bundle heat exchangers are used for the evaporator, absorber, condenser and desorber.
Usually, equilibrium state simulations are used to calculate the specific circulation ratio of the solution and the coefficient of performance (COP) to compare working pairs to each other. To estimate the cooling capacity, simulations which take only the heat transfer into account are common. However, experimental data indicate that mass transfer plays an important role, especially when using ionic liquids (IL), and therefore, the approaches are not sufficient for explaining the behaviour of ILs in absorption chillers.
Different ILs and LiBr with water as refrigerant will be investigated in the paper at hand. At first, equilibrium and measured specific circulation ratios will be compared to each other to enable a comparison to the literature. In essence, it can be assumed that resistance to mass transfer will reduce the composition change which takes place in generator and absorber. Consequently, to achieve a given cooling capacity a larger circulation rate will be required. In line of this thought, an approach for distinguishing the heat and mass transfer capabilities of the working fluids in a specific exchanger design will be used, to determine, whether the disagreement between equilibrium and measured circulation ratios originates from heat or mass transfer restrictions or both.
The results of the ILs vary vastly and differ from the ones of LiBr. While the cooling capacity of LiBr is mainly restricted by the heat transfer, for the ILs and LiBr with low additive content, the heat transfer is less important.

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Pages: 13 p.

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Details

  • Original title: On the deviation from equilibrium state and the heat and mass transfer capabilities of ionic liquids in absorption chillers.
  • Record ID : 30031620
  • Languages: English
  • Subject: Technology
  • Source: Proceedings of the 26th IIR International Congress of Refrigeration: Paris , France, August 21-25, 2023.
  • Publication date: 2023/08/21
  • DOI: http://dx.doi.org/10.18462/iir.icr.2023.0497

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