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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.

Noise reduction of Automotive HVAC systems is a hard task because of the highly complicated and very sensitive turbulent flow in the blower fan unit. First, we identified the location of noise sources by the Sound Intensity (SI) method, then we investigated the flow pattern by the oil-mist method. As a result, two main noise generation mechanisms have been identified. One mechanism is generated by the interaction of the strong steady flow of air in the unit with the fan wheel, and the other is from the turbulent flow between the fan blades. Results: A new fan blade design was developed that had improved control of the turbulent flow, and which configuration caused a noise reduction of 2 dB-A over current blown fan systems.

The use of copper heat exchangers was the major trend in large transportation vehicles due to their satisfactory performance in severe conditions. However, heat exchangers made of aluminum for the heat exchanger part and glass-fiber reinforced modified polyamide resin for the coolant tank have been developed due to the demand for weight and cost reduction as well as productivity improvement. In the injection molding of these large tanks, warping is an engineering concern. Therefore, by analyzing the warping with the use of injection molding simulations, we have developed a production method that is capable of satisfying the dimensional requirements without any dimension correcting process.

Heat flow phenomena in the heater unit of an automobile air conditioning system have been analyzed by direct simulation, solving the Navier-Stokes' equation in which an upwind finite difference method of third-order accuracy is adopted with a 2-D model. The analytical results presented visually to ascertain air and heat flows in the heater unit. In addition, a comparative experiment was carried out to compare test results with calculated results. The heater unit in the air conditioning system controls the temperature of air in the automobile. The heater unit consists of a unit inlet, outlet, mixing door and heater, as shown in Fig. 1 (1). Air, entering the heater unit inlet is mixed with warm air heated by the heater to a suitable temperature, and then blown out of the outlet. The shape and size of the heater unit are restricted by the size of an automobile's engine compartment and the layout of other auxiliary devices.

Due to a surge of public interest in environmental conservation in recent years, the automobile industry now faces technological innovations to provide environmentally friendly engines. Among these engines, direct injection engines have become the primary candidates for use in the near future due to their lower fuel consumption and CO2 emission in comparison with conventional uniform charge combustion engines. Innovative technologies of these engines demand that the air conditioning system be of “a power saving design” and “compatible with the engine.” In these new requirements, the variable displacement compressor is more advantageous than other types, which will be shown in this paper. The paper will also explain the mechanism that can bring a larger fuel saving effect through “optimal control” of a variable displacement compressor by its external control.

These days the alignment of radiator and condenser in the vehicle front is the major trend. Due to this alignment, the radiator characteristics are one-sidedly affected by condenser radiating heat, which will cause deterioration in the engine cooling performance at high engine speed and high heat load vehicle operation when air conditioning (A/C) capacity becomes excess. Studies were made on the effects that condenser operation have on radiator characteristics. Results showed that controlling the condenser operation characteristics will provide improved A/C and engine cooling performance in the vehicle system. This paper will discuss the details of the above-mentioned analyses with focus on the vehicle characteristics of front engine, front drive (FF) vehicles and the results of vehicle proving tests.