The thermo-hydrodynamic performance of an automotive radiator, used as the external heat exchanger of an auto air-conditioning system, was analysed and presented in this article. The radiator was a kind of cross-flow air-liquid compact heat exchangers with rectangular minichannels and louvered thin-plate fins. The radiator was installed in a secondary fluid loop of the vapour compression refrigeration unit in a custom auto air conditioning system. The refrigeration unit and its two secondary fluid loops were operated at different heat load conditions for summer conditions. Experimental data including temperatures, pressures, and flow rates were collected at steady-state conditions. Heat transfer and pressure drop correlations for the glycol-water mixture and air flowing through the radiator were presented and discussed. On the glycol-water side of the radiator, the enhancements inside the rectangular minichannels promoted turbulent flow and increased heat transfer in comparison with the smooth rectangular channels. The results showed that, even at low Reynolds number (less than 1000), the Nusselt number of the glycol-water flow within the minichannels was not constant but increasing with Reynolds number. This might be caused by the enhancements on the minichannel walls. On the air-side, the thin-plate fins were sandwiched between the two neighbouring parallel channels and louvered vertically along the air flow passages. These louvers promoted turbulence and reduced the boundary layer thickness of the air flowing cross the radiator. The results of this study may be used in the design of this type of minichannel compact heat exchangers because the experimental data were collected for operating conditions and flow rates that are typically found in automotive air conditioning systems.
Thermal-fluid characteristics of an automotive radiator used as the external heat exchanger in an auto air conditioning system
2005
9 Seiten, 10 Bilder, 2 Tabellen, 12 Quellen
Conference paper
English
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