Comparison and selection of experimental designs for the characterization of scroll and reciprocating compressors: Adjustment of polynomial models with compact experimental samples

Abstract

The use of refrigeration equipment and heat pumps is a widely used solution by manufacturers in the industry. Selecting components for this equipment and simulating their behavior require a thorough understanding and effective characterization of the compressor. In this sense, the standard AHRI-540 is the most used one to characterize compressor performance (Ẇc and ṁref) considering polynomial models of 10 coefficients. Unfortunately, this standard does not offer information about where to perform the required experimental measurements for the model adjustment. Drawing on these precedents, this paper investigates various Design of Experiments methodologies to identify the most efficient approaches for characterizing both scroll and reciprocating compressors with minimal experimental points. The study aims to develop a straightforward methodology for optimal point selection, ensuring precise compressor characterization while minimizing experimental costs. For this purpose, two datasets from two Copeland scroll compressors – ZP21K5E-PFV and ZS21KAE-PFV – with massive test campaigns have been employed. Both compressors were subjected to a substantial number of experimental points (1097 and 866) across different suction conditions (SH=11 K, SH=22 K, Tsuc=18 °C) and different refrigerants (R134a, R32, R410A, R404a, …). In a first step, this study presents the design of experimental matrices for characterizing efficiently the energy consumption and mass flow rate in scroll compressors. Additionally, the energy consumption is also characterized from the specific energy consumption (Ẇesp), i.e., the energy consumption divided by the mass flow rate. Considering that the specific energy consumption obtains equal dependencies between scroll and reciprocating compressors, the matrices performed for the specific energy consumption are also suitable for the characterization of reciprocating compressors, also allowing to obtain compact experimental matrices with a low number of points.