Modeling and Analysis of Scroll Compressor Conversion into an Expander for Rankine Cycles

Abstract

In this article, we analyze through a model the use of a refrigeration scroll compressor as expander for power generation applications with small-power Rankine cycle. A scroll compressor is selected from a refrigeration manufacturer catalog used for the study. Based on catalog data and our model the specific parameters of the compressor such as built-in volume ratio and leakage coefficient are determined through mathematical regression. The expander model is used to predict the efficiency and other important parameters of the scroll expander. The expander operation within Rankine cycle is studied and compared for several working fluids. The expander does not operate optimally when converted from a compressor without any modifications. Therefore it is developed a method and a code for determining the geometry of the expander with respect to rolling angle in order to obtain the built-in volume ratio which assures better efficiency of the Rankine heat engine. The article reports a parametric study with respect to scroll geometry, working fluid, and operating conditions. The optimum rotational speed varies from 1,500–2,500 RPM depending on operating pressure. The method of conversion of scroll compressor into expander may be useful in development of cost-effective expanders for small scale Rankine cycles for power and heating generation from renewable energy resources.

Keywords:

• Compressor
• Expander
• Rankine cycle
• Heat recovery
• Heat engines