Variable Orifice Valve Development and A/C System Performance Testing 971824

First introduced in 1995, the concept of a temperature-responsive Variable Orifice Valve to control refrigerant flow (patent # 5,479,786) has been further developed for use in automotive refrigerant systems. This device is an alternative, to the expansion devices currently used in automotive refrigerant systems and offers the best features of a thermal expansion valve system (similar high ambient performance ) and of a fixed orifice tube system (low cost, high reliability & performance at lower ambients). Typical automotive refrigerant system operation includes wide variations in condenser air flow and refrigerant pressure. The resultant condenser exit refrigerant temperature is a very stable input parameter for the control of this variable orifice valve (VOV). The optimized refrigerant flow restriction provided by the VOV, on fixed orifice tube systems, has resulted in significantly lower evaporator discharge air temperatures under various driving conditions at ambients of 100° F and above. Vehicle performance improvements achieved by use of a VOV will be examined in this paper under conditions such as, cool down, highway driving, and city traffic.

This paper will discuss the design and production validation of this device completed to date. The flow regulation characteristics, thermal response of the valve, and the calibration techniques employed, will be discussed, as well.

Any specific vehicle refrigerant system can be measured to predict potential performance improvements. This measurement technique is used to size and calibrate a VOV. This technique along with refrigerant charge level considerations are necessary to optimize each application.