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Dynamic behaviour of mobile air-conditioning systems.

Author(s) : GADO A., HWANG Y., RADERMACHER R.

Type of article: Article

Summary

Passenger cars and light trucks consume 80% of the total oil imported by the United States. Mobile air-conditioning systems (MACs) increase vehicle fuel consumption and exhaust gas emissions. They operate most of the time in a transient state. To investigate the dynamic behaviour of a typical R-134a MAC, the "dynamic simulator," which is a laboratory transient test facility for MACs, was utilized. The facility depends on simulation software that measures the conditions of the air supplied by the MAC and subsequently adjusts the conditions of the air returning to the MAC, depending on the results of a thermal numerical model of the car cabin. The transient tests conducted include pull-down, drive-cycle tests and drive-cycle tests with a thermostat. The results show that the most energy-efficient method to pull down the air temperature inside a hot-soaked cabin is to start with fresh air, as long as the temperature in the cabin exceeds that of the ambient temperature, and then switch to recirculated air. The effect of the thermostat action on the relative humidity inside the car cabin shows that the relative humidity inside the cabin increases due to re-evaporation of the condensate on the evaporator. This re-evaporation of the condensate during the compressor-off period adds cooling load to the MAC when it starts again. This study provides some insights on the dynamic behaviour of the MAC and proposes a new transient test method in the laboratory and a new transient performance index.

Details

  • Original title: Dynamic behaviour of mobile air-conditioning systems.
  • Record ID : 2008-1783
  • Languages: English
  • Source: HVAC&R Research - vol. 14 - n. 2
  • Publication date: 2008/03

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