Thermodynamic evaluation of two portable cooler running with reciprocating and mini-rotary compressors

Abstract

Small-capacity refrigeration has got an increasing attention of the consumer
market. In addition to the efficiency of electric equipment, the demand for
compactness has also become a relevant requirement. Among the
alternatives available to cool down small cabinets, mechanical vapor
compression refrigeration remains prominent due to its satisfactory
performance when compared to other cooling technologies. Compressor
industries have invested in the development of compact and efficient
products, exploring different compression principles for small-capacity
applications, as is the case of mini-rotary compressors. In this context, the
objective of the present work is to assess the thermodynamic performance
of a 38-liter portable vapor compression refrigeration system running with
two different compressors designed for small-capacity applications: minirotary
and reciprocating. Experimental tests were carried out at three
different ambient temperatures (16, 25 and 32 °C) in order to obtain the key
performance parameters for each compressor (e.g., power consumption,
cooling capacity, internal air temperature, and the condensing and
evaporating temperatures). Finally, thermodynamic analyses were
conducted to account for the internal and external irreversibilities by means
of second law efficiencies, allowing for a comparison of the system
performance running with both compressors in the same thermodynamic
grounds. Albeit a refrigeration (second law) efficiency by 25% higher was
observed for the reciprocating compressor, it provided a smaller cooling
capacity and, therefore, led to a higher pull-down time.