A Semi-Theoretical Model for Predicting Refrigerant/Lubricant Mixture Pool Boiling Heat Transfer

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A Semi-Theoretical Model for Predicting Refrigerant/Lubricant Mixture Pool Boiling Heat Transfer (750 KB)

 

Kedzierski, M. A.

International Journal of Refrigeration - Revue Internationale Du Froid , Oxon, England - May 01, 2003

Keywords:

boiling , enhanced heat transfer , non-adiabatic lubricant excess surface d , pool boiling , R123 , refrigerant/lubricant mixtures , smooth surface

Abstract:

This paper outlines the development of a semi-theoretical model for prediction the pool boiling heat transfer of R123/lubricant mixtures on a roughened, horizontal flat pool-boiling surface. The predictive model is based on the mechanisms involved in the formation of the lubricant excess layer that exists in the heat transfer surface. The lubricant accumulates on the surface in excess of the bulk concentration via distillation from the bulk refrigerant/lubricant mixture. As a result, excess lubricant resides in a thin layer on the surface and influences the boiling performance, giving either an enhancement or degradation in heat transfer. A dimensionless excess layer parameter and a thermal boundary layer constant were fitted to data in an attempt to generalize the model to other refrigerant/lubricant mixtures. The model requires both transport and thermodynamic refrigerant properties and the lubricant composition, viscosity and critical solution temperature with the refrigerant as input. The model predicts the boiling heat transfer coefficient of three different mixtures of R123 and lubricant to within ± 10%. Further work is required to extend or validate the model to other refrigerants and lubricants.

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National Institute of Standards and Technology
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