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Refrigerant and oil charge distribution in refrigeration systems: MAC unit example.

Raspodela rashladnog fluida i ulja u rashladnim sistemima na primeru automobilskog klima-uredaja.

Number: 24

Author(s) : HRNJAK P., JIN S.

Summary

The paper presents a semi-empirical model to predict refrigerant and lubricant inventory in both microchannel condenser and plate-and-fin evaporator of an air conditioning system. In the model, heat exchanger was discretized into finite volumes. Temperature, pressure and mass inventory were calculated by applying heat transfer, pressure drop and void fraction correlations to each of these volumes. Refrigerant and lubricant were treated as a zeotropic mixture with a temperature glide. As refrigerant evaporates or condenses, thermophysical properties were evaluated accordingly with the change of lubricant concentration. Oil was assumed to be retained in refrigerant oil mixture at concentration that was changing during phase change in condenser and evaporator. Experimental data with R134a and PAG oil indicated 20% agreement with the model of refrigerant and oil retention in the evaporator. However, in the condenser, lubricant mass was consistently under-predicted while refrigerant mass was predicted same as in evaporator (within 15% error). Moreover, the lubricant under-prediction became more significant at higher Oil Circulation Ratio (OCR). The analysis showed that the lubricant was separated from the flow in the condenser header and started to accumulate in the bottom channels. The temperature profile in the infrared image supported this hypothesis, as the temperature of the bottom channels was much lower.

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Pages: 10 p.

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Details

  • Original title: Raspodela rashladnog fluida i ulja u rashladnim sistemima na primeru automobilskog klima-uredaja.
  • Record ID : 30013422
  • Languages: English
  • Source: Zbornik radova. 45. Medunarodnikongres i izložba o grejanju hladenju i klimatizaciji./ Proceedings. 45th International congress and exhibition on heating, refrigeration and air conditioning (HVAC&R).
  • Publication date: 2014/12/03
  • Notes:

    Abstract in Serbian


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