Theoretical evaluation of trans-critical CO2 systems in supermarket refrigeration. Part II: System modifications and comparisons of different solutions

Abstract

t r a c tThe performance of CO 2 refrigeration systems strongly depends on the operating conditions. The specific characteristics of low critical temperature and high operating pressure limit its applications and imply the implementation of different control strategies. This study compares the performance of different CO 2 system solutions for supermarket refrigeration with R404A system. Some possible modifications and improvements on the CO 2 system have been investigated. The COP of the investigated CO 2 system solution can be improved by about 3-7% along the ambient temperature range of 10-40 C. The annual energy consumption calculations in three different climates; cold, moderate and hot, show that the centralized trans-critical CO 2 system is good solution for cold climates whereas the NH 3 -CO 2 cascade system has the lowest energy consumption in hot climates. Both systems proved to be good alternatives to R404A DX system for supermarket refrigeration.

Influence of the superheat associated to a semihermetic compressor of a transcritical CO2 refrigeration plant

“…With this empirical model the main operating variables of the compressor can be calculated. They are the volumetric efficiency (5), the SH SC (6), the compression efficiency (7) (which takes into account isentropic and mechanical efficiencies) and the discharge temperature (8). The chosen variables to adjust the model were the motor inlet (P Mot ) and compressor discharge (P Dis ) pressures, the refrigerant inlet temperature to the compressor (T Mot ), the specific suction volume (v suc ) and the compressor speed (N).…”

“…The chosen variables to adjust the model were the motor inlet (P Mot ) and compressor discharge (P Dis ) pressures, the refrigerant inlet temperature to the compressor (T Mot ), the specific suction volume (v suc ) and the compressor speed (N). The expressions (5)- (8), which depend on the variables analyzed in Section 3, were selected in order to achieve the best fit to the experimental data obtained from the compressor.…”

“…Coefficients for expressions (5)- (8) and their maximum estimation errors are displayed in Table 3, and their validity range in Table 4.…”

“…Its utilization in the car industry [1][2][3], in heat pumps [4,5] or in commercial applications [6][7][8] proves the great scientific and technical interest that this refrigerant has aroused in the recent years, mainly due to its excellent environmental and safety properties [9]. At present, research works in progress deal with upgrading the energetic efficiency of the installations by developing either new components [10] or novel operating configurations [11,12].…”

Developing Information on Energy Savings and Associated Costs and Benefits of Energy Efficient Emerging Technologies Applicable in California

“…Also, it is more suited for larger systems (Reulens, 2009). In the data table we use the theoretical energy consumption in a moderate climate of such a cascade system with that of a HFC system for comparison (Sawalha, 2008).…”