An Experimentally Validated Model for Predicting Refrigerant and Lubricant Inventory in MAC Heat Exchangers

Event
SAE 2014 World Congress & Exhibition
Authors Abstract
Content
The paper presents a semi-empirical model to predict refrigerant and lubricant inventory in both evaporator and condenser of an automotive air conditioning (MAC) system.
In the model, heat exchanger is discretized into small volumes. Temperature, pressure and mass inventory are calculated by applying heat transfer, pressure drop and void fraction correlations to these volumes respectively. Refrigerant and lubricant are treated as a zeotropic mixture with a temperature glide. As refrigerant evaporates or condenses, thermophysical properties are evaluated accordingly with the change of lubricant concentration.
Experimental data is used to validate the model. As a result, refrigerant and lubricant mass is predicted within 20% in the evaporator. However, in the condenser, lubricant mass was consistently under-predicted while refrigerant mass was predicted within 15% error. Moreover, the lubricant under-prediction becomes more significant at higher Oil Circulation Ratio (OCR). The analysis showed that the lubricant is separated from the flow in the condenser header and starts to accumulate in the bottom channels. The temperature profile in the infrared image supports this hypothesis, as the temperature of the bottom channels is much lower. After correcting this by counting in the bottom lubricant mass, the model predicts condenser lubricant mass consistently within 15% error.
Meta TagsDetails
DOI
https://doi.org/10.4271/2014-01-0694
Pages
12
Citation
Jin, S., and Hrnjak, P., "An Experimentally Validated Model for Predicting Refrigerant and Lubricant Inventory in MAC Heat Exchangers," SAE Int. J. Passeng. Cars - Mech. Syst. 7(2):769-780, 2014, https://doi.org/10.4271/2014-01-0694.
Additional Details
Publisher
Published
Apr 1, 2014
Product Code
2014-01-0694
Content Type
Journal Article
Language
English