All-year vehicle simulation with analysis of capacity control of R-134a and R-744 piston compressors for coach HVAC systems

摘要

The state of the art for controlling air-side cooling capacity in conventional omnibus HVAC systems is the reheat of the cooled air. This method is pragmatic, although energetically highly inefficient. A more efficient way is to control the cooling capacity depending on actual cooling capacity demand. This is commonly achieved by adjusting the capacity of the refrigerant compressor. Various methods and technical solutions are feasible for adapting the capacity of the typical refrigerant compressor used in omnibus HVAC systems. For this purpose, speed control with a continuously variable transmission (CVT) or speed control by means of an innovative two-speed pulley gearbox based on a planetary gearbox as well as cylinder bank shutdown by suction gas interlock can be used. Also feasible is the novel method of combining speed control by means of a two-speed pulley gearbox and cylinder bank shutdown by suction gas interlock. The main object of the present study is to identify potential fuel savings and opportunities to improve cooling capacity through the use of the refrigerant compressor capacity adaption methods and techniques mentioned above. In respect thereof, this study looks at an R-134a and an R-744 coach air conditioning system. For this purpose, a vehicle simulation model was developed and three climatically different, realistic driving route scenarios (Germany, Portugal/Spain and India) are considered within this vehicle simulation. Based on these three driving route scenarios, virtual driving scenarios are performed on every 15~(th) of the month for a representative year to determine average annual fuel consumption.