A study on scroll compressor conversion into expander for Rankine cycles

In this paper, we investigate using a refrigeration scroll compressor as expander for power generation applications with a Rankine cycle. The methodology employed here has three steps: In the first step, a scroll compressor is selected from a refrigeration manufacturer catalog. Based on catalog data and our simplified model, the specific parameters of the compressor such as the built-in volume ratio and leakage coefficient are determined through mathematical regression. In the second step, the parameters and the efficiency of the Rankine cycle are determined, which use the selected scroll machine in reverse, namely as expander, without any geometrical modifications. The range of temperatures and pressures are kept the same as that characterizing the compressor operation. A simplified expander model is used to predict the efficiency of the prime mover and of the Rankine cycle. A range of working fluids are considered and compared. The expander does not operate optimally when converted from a compressor without any modifications. In the third phase, the geometry of the expander is modified with respect to the rolling angle only in order to obtain the appropriate built-in volume ratio which assures better efficiency of the Rankine heat engine. This paper also presents a parametric study in terms of geometry, working fluid and operating conditions. Copyright , Oxford University Press.