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Current production automotive airconditioning systems have demonstrated the lower thermodynamic efficiency of HFC-134a versus traditional CFC-12 refrigerant. A loss in cooling performance was realized at low speeds and idle with the serpentine condenser and HFC-134a. However, with the proper system modifications and materials selection, HFC-134a has been successfully tested in one particular mobile air conditioning application. Better A/C system performance was achieved with HFC-134a when the OE serpentine condenser was replaced by a 30% greater heat transfer capacity condenser. This more efficient design is called the multiflow condenser. It also offers 50% less weight and 20% less refrigerant when compared to the present serpentine configuration on the application tested.

Engine Cooling and Air Conditioning tests were performed using a sports utility vehicle with a V-6 engine. The original vehicle was equipped with an engine driven fan. This vehicle was modified by adding electric motor driven fans, air path sealing and advanced heat exchangers in a predetermined test configuration. Engine cooling performance and air conditioning performance were evaluated at each step. Identical grade load and idle tests were conducted with this vehicle at each step. The V-6 sports utility vehicle was selected due to its use of an engine driven fan. The grade load of 8.7% was selected due to off road use by the consumers. The results of the testing showed that engine cooling performance and air conditioning performance were improved by using electric motor driven fans, air path sealing and advanced heat exchangers.

Re-design of the thermostatic expansion valve (TXV) was necessary for the efficient use of HFC-134a refrigerant in mobile air conditioning applications. Laboratory work demonstrated the need for changing both valve characteristics and inside design. The use of the new expansion valve resulted in low HFC-134a system discharge pressures with either the serpentine or “proprietary” multiflow condensers. Vehicular wind tunnel and road tests both showed the HFC-134a A/C system to have better cooling performance and similar discharge pressures at less refrigerant charge than the conventional CFC-12 system, when using the new expansion valve and multiflow condenser.