Modeling of R-410A variable capacity compressor with Modelica and experimental validation

• Developed novel experimental testbed for short cycling scroll compressors.
• Investigated time-averaged parametric model of short cycling scroll compressor.
• Studied parametric model with time-varying volumetric and isentropic efficiencies.
• Investigated a dynamic model of a short cycling scroll compressor.
• Models generally showed good agreement with experimental data.

This paper presents an analysis of modeling methods for a short cycling, R-410A scroll compressor. Two parametric efficiency models of the short cycling scroll compressors are investigated, one with steady-state mean, and one with time varying efficiencies. Additionally, a dynamic model of a short cycling scroll compressor that incorporates scroll geometry, leakage, and a mathematical approximation of the digital capacity mechanism has been developed and verified against experimentally obtained data. Agreement with data for all methods was generally good, though in the dynamic model refrigerant mass flow was found to match observations when neglecting leakage. To validate the proposed models, a novel experimental testbed was developed by retrofitting a 15 ton nominal capacity rooftop heat pump with a short cycling scroll compressor. Unit operating conditions were varied in a parametric fashion using a large scale psychrometric chamber and the compressor transient performance was evaluated at full and part loads.