Influence of refrigerant charge and air inlet temperatures on the performance of an automotive air conditioning system.

One of the parameters that most affect the performance of automotive air conditioning systems is the refrigerant charge in the system. The loss of refrigerant can be caused by small leaks in hoses, gaskets and connections permeability of the refrigerant lines, accelerated by the operating conditions of the system, such as high vibration, shock, etc. The overcharge condition can be caused mainly due to system maintenance, where conditions control and charge method are not adequate. To determine these effects, tests were performed using an experimental bench with an automotive air conditioning system operating with R-134a and a block type thermostatic expansion valve. The refrigerant charge ranged from 850 to 1850 g, assuming a nominal charge of this system around 1400 g. The results showed that at a low charge condition the system was more sensitive than to overload charge condition, operating in a wide range of charges under similar conditions. From the definition of the optimum charge, the effects of air temperatures at the inlet to the condenser and evaporator also have been analysed and the results showed.