Two Stage Orifice Tube - Performance in a Cycling Clutch Orifice Tube System

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. The two stage orifice tube is controlled with condenser refrigerant discharge fluid temperatures and has proven to be more stable than an expansion valve. The two stages represent two flow passages in parallel.