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CO2 as an alternative refrigerant for applications below -50°C.

Number: pap. 2105

Author(s) : LANGEBACH R., HESSE U., XU Y.

Summary

Carbon dioxide (CO2) is a well-known and established refrigerant with many advantageous properties and therefore used in many applications. However, the lowest achievable temperature is usually limited by the triple conditions at approximately 217 K and a corresponding pressure of 5.2 bar. Below these triple conditions CO2 only exists is gaseous and solid state. Commonly, the occurrence of solid particles in vapour compression cycles is carefully avoided and hence CO2 in solid state no option at all. With respect to increasing legal restrictions and upcoming bans for fluorinated refrigerants CO2 might be also a reasonable alternative in low temperature refrigeration – despite the obstacles with the solid phase. In this paper we give an overview on previous research activities with CO2 sublimation cooling in literature. Further, the theoretical efficiency of a CO2 cycle with a sublimation temperature of 198 K is compared to a conventional R404A/R23 cascade. It can be shown that a CO2 sublimation cycle can exceed the cycle efficiency of conventional systems. Finally, a closer look to the heat transfer of solid-gaseous flow in the sublimation heat exchanger is given and challenges are discussed.

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Pages: 10

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Details

  • Original title: CO2 as an alternative refrigerant for applications below -50°C.
  • Record ID : 30018925
  • Languages: English
  • Source: 2016 Purdue Conferences. 16th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2016/07/11

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