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With the advent of new technologies and rigorous research and development work going on vehicle engines, cars are becoming quieter and more refined than ever before. This has led to the observance of subjective noises being audible to passenger compartment which were earlier masked behind engine noise. The vehicle HVAC system has several moving parts and transient flow of refrigerant which can cause certain types of irritant noise. Thus having a refinement in of air-conditioning (AC) system would aid us in cutting down on this parasitic noise source. Thus noise refinement should be one of the important parameters during the design and development of the Heating, Ventilation and Air-Conditioning (HVAC) system for a vehicle program.

This paper and presentation compare the thermal, economic and climate performance of existing direct expansion motor vehicle air conditioners (DX-MACs) using hydrofluorocarbon (HFC)-134a (global warming potential (GWP) =1300) with secondary-loop MACs (SL-MACs) using hydrofluoroolefin (HFO)-1234yf (GWP < 1) and HFC-152a (GWP = 138), both of which satisfy the European Union (EU) and Japan F-gas regulations and are listed as acceptable by the US Environmental Protection Agency (US EPA). In addition to a technical review of the SL-MAC system, the paper includes a part-by-part system manufacturing cost comparison and itemized ownership cost comparison taking into account fuel savings and reduced maintenance. The paper is timely because the Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer now requires both developed and developing countries to phase down the production and consumption of HFCs and at the same time encourages increases in energy efficiency.

In an automotive air conditioning system, evaporator is well designed for effective heat transfer between refrigerant and air flowing over the evaporator. This cold and dehumidified air obtained at evaporator is then supplied to passenger cabin. There are various parameters like air flow over evaporator, ambient temperature, humidity condition and condensate drain mechanism which can cause frost formation over the evaporator core. This study presents the probable causes of frost formation and their effects on the performance of evaporator and thus affecting overall performances of the automotive air conditioning system. In this study effect of variation in four major independent factors such as poor response of thermistor, undercharged refrigerant system and overcharged refrigerant system, drop in air flow by blower due to clogged air-filter, and also the effect of type of compressor has been studied.

With the passage of the Kigali Amendment to the Montreal Protocol, HFC-134a refrigerant will be phased down in all markets worldwide, including those where automotive companies have been slow to embrace HFO-1234yf. Engineers are currently being challenged to design MAC systems using alternate low GWP refrigerants that are allowed by regulations, and are simultaneously cost-effective to manufacture, energy efficient, safe, reliable, affordable for consumers, and also suitable in electrified vehicles.