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A study of a wavy fin and tube CO2 evaporator coil for a secondary loop in a low temperature refrigeration system.

Author(s) : OUZZANE M., AIDOUN Z.

Summary

Due to its favourable thermophysical and transport properties as well as environmental advantages, carbon dioxide is among the natural fluids that represent a potential alternative to synthetic refrigerants, namely HCFCs and HFCs, which are harmful to the environment (ozone depletion and greenhouse warming effects). Carbon dioxide may be used as a refrigerant (primary fluid, usually at low temperatures) or as a secondary loop fluid with phase change at medium temperatures. In both cases the benefits are important in terms of compression and pumping powers. In this contribution, we present the diameter effect on both hydraulic and thermal performance of a CO2/air evaporator coil at low temperature typically used in a supermarket environment. To this aim a mathematical model based on the conservation equations of mass, momentum and enthalpy has been developed. The coil was represented by a set of tiny control volumes and the solution procedure of the resulting equations was based on the forward marching technique. The results were compared with experimental data obtained on our laboratory test bench and the agreement was very satisfactory. It was shown that CO2 pressure drop was very limited with a correspondingly low temperature glide along the coil. Hence, more passes could be used with a smaller tube diameter leading to more circuit arrangements and resulting in higher capacity and lower coil volume than ordinarily used. Because of high air thermal resistance, the benefits of the CO2 are more important on the internal side in terms of low internal pressure loss.

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Pages: pp. 95-102

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Details

  • Original title: A study of a wavy fin and tube CO2 evaporator coil for a secondary loop in a low temperature refrigeration system.
  • Record ID : 2010-1078
  • Languages: English
  • Source: Projektowanie i eksploatacja przyjaznych srodowisku systemów chlodniczych i klimatyzacyjnych. Miedzynarodowa konferencja. XL Dni chlodnictwa.
  • Publication date: 2008/10/15

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