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Finned-tube heat exchangers: the optimization of the internal circuits for condensers and evaporators.

[In Italian. / En italien.]

Author(s) : FABBRETTI V., FORNASIERI E.

Summary

The paper deals with the optimization of the design of the circuits of finned coils with condensing or evaporating refrigerants inside tubes. Two aspects are investigated: a) the value of the refrigerant flow rate, i.e., the determination of the optimal number of individual circuits, and b) the flow arrangement, i.e., whether parallel or counter flow is preferable. As for the first point, the optimization results from the best trade-off between an increased value of the heat transfer coefficient and an increased value of the pressure drop, something that adversely affects the temperature difference between the fluids. For condensing fluid, the paper provides the optimal values of the mass velocity (kg/m2.s) as functions of the external heat transfer coefficient of the coil and its operating temperatures. The best flow arrangements depend on the effects of the variation in the saturation temperature, resulting from the pressure drop, as well as on the effect of the variation in the heat transfer coefficient as a function of vapour quality; counter flow ought to preferred for condensers, parallel flow for evaporators, except when using thermostatic expansion valves.

Details

  • Original title: [In Italian. / En italien.]
  • Record ID : 1997-3248
  • Languages: Italian
  • Source: Condizionamento, riscaldamento, refrigerazione: innovazioni e tendenze. 37e Convegno annuale AICARR./ Air Conditioning, Heating and Refrigeration: Innovations and Trends. 37th annual conference of AICARR.
  • Publication date: 1996/03/29
  • Document available for consultation in the library of the IIR headquarters only.

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