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Heat transfer analysis of R134a, R1234ze(E) and R513A inside falling film and flooded evaporators with enhanced surface tubes: experimental data and comparison with empirical correlations.

Number: 0623

Author(s) : CENSI G., PADOVAN A.

Summary

In refrigeration systems, the use of refrigerants with low GWP (Global Warming Potential) in falling film evaporators contributes to the reduction of greenhouse gas emissions. Indeed, the falling film heat transfer efficiency is close to that obtained by pool boiling, but the refrigerant charge is lower. For instance, the evaporator analysed in the present work allows to save up to 40% of the total charge. This paper presents experimental heat transfer data of R134a, R1234ze(E) and R513A in a falling film and a flooded evaporator with the same enhanced tube. In both heat exchangers the chilled water flows in four different passes, from bottom to top, and for each of them the heat flux and the heat transfer coefficient are determined. This allows to map the performances of the evaporators at different heights of the tube bundle. No significative variations are found in flooded evaporation, whereas the heat transfer coefficient of the falling film evaporator is influenced by the zone considered: it is greater in the upper parts, where the heat flux is lower, and the film Reynolds number is higher. The tests are repeated by inverting the water flow, from top to bottom: the performance of the flooded evaporator remains almost unaffected, while for the falling film evaporator it worsens, consistently with the results previously obtained. The experimental data are then compared with some empirical correlations from the literature. To improve their predictive accuracy, they need to be optimized as they have been developed for limited conditions.

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Pages: 12 p.

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Details

  • Original title: Heat transfer analysis of R134a, R1234ze(E) and R513A inside falling film and flooded evaporators with enhanced surface tubes: experimental data and comparison with empirical correlations.
  • Record ID : 30031641
  • 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.2023.0623

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