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The purpose of this paper is to present an alternative to the fixed orifice tube used in automotive refrigeration systems. This paper will examine the improvements that are now possible at high ambient temperature conditions by using a two-stage orifice tube. The improvements include significantly lower evaporator discharge air temperatures and lower refrigerant charge amounts. The proposed new expansion device, used in a Cycling Clutch Orifice Tube system (CCOT), will raise the high ambient, low speed performance to that of a Cycling Clutch Thermostatic eXpansion Valve system (CCTXV). The two stage orifice tube embodies the best operating features of the expansion valve system (idle speed operation), and that of the fixed orifice tube system (highway speed performance, low cost, and high reliability). This paper will conclude with a discussion of the design and control features of this proposed new device.

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).