High phase-separation efficiency auto-cascade system working with a blend of carbon dioxide for low-temperature isothermal refrigeration

Michał Sobieraj , Marian Rosiński

Abstract

Ahighphase-separationefficiencyauto-cascaderefrigeration(ACR)systemworkingwithazeotropicmixtureofCO2is proposed in this study. The selection of a high boiling-point component is analysed. A novel zeotropicmixture consisting of a high CO2(R744) mass fraction together with isobutane (R600a) as a carrier fluid isproposed. An experimental setup was designed, built, and verified to study the ability of the ACR to provideisothermal refrigeration at temperatures lower than the R744 triple-point temperature. The setup employs arecuperative heat exchanger (RHX) for the maximum phase-separation efficiency. The effect of the refrigerantmass charge on the ACR operation was examined. The temperature distribution across the internal heat ex-changers (IHXs) was studied as well. The results revealed that the system was very sensitive to the refrigerantmass charge. With a low mass charge, the ACR did not operate correctly owing to the pinch points occurringbetween the hot and cold ends of the IHXs. High mass charge resulted in increased power consumption and adecreasedcoefficientofperformance(COP).Moreover,testswereconductedtoexaminetheabilityoftheACRsystem, working with a binary mixture of R744/R600a, to provide isothermal refrigeration with different eva-porator heat loads. The ACR system was compared in terms of the evaporation pressure and mass flow to acascade system working with trifluoromethane (R23) in the low stage. The ACR system can be a promisingalternativetocascadesystemsworkingwithR23.ThemixtureofR744/R600apresentedasignificantdecreaseinthe global warming potential (GWP) compared with R23. Near-isothermal evaporation was possible with thismixtureoverarangeofvapourqualityvalues.TheapplicationrangeofCO2wasextendedtotemperatureslowerthan the CO2triple-point temperature, using isobutane as a solvent for dry ice. The enthalpy–mass fractiondiagrams incorporating a solid fraction area were constructed for the graphical representation of the ACRsystem
Author Michał Sobieraj (FEE / DHV)
Michał Sobieraj,,
- Department of Heating and Ventilation
, Marian Rosiński (FEE / DHV)
Marian Rosiński,,
- Department of Heating and Ventilation
Journal seriesApplied Thermal Engineering, ISSN 1359-4311, (N/A 140 pkt)
Issue year2019
Vol161
Pages1-11
Publication size in sheets0.5
Article number114149
Keywords in EnglishCarbon dioxide, Isobutane, R744, Auto-cascade, Dry ice, Sublimation
ASJC Classification2102 Energy Engineering and Power Technology; 2209 Industrial and Manufacturing Engineering
DOIDOI:10.1016/j.applthermaleng.2019.114149
URL https://doi.org/10.1016/j.applthermaleng.2019.114149
Languageen angielski
File
1-s2.0-S1359431119320095-main.pdf 2.86 MB
Score (nominal)140
Score sourcejournalList
ScoreMinisterial score = 140.0, 25-01-2020, ArticleFromJournal
Publication indicators WoS Citations = 0; Scopus SNIP (Source Normalised Impact per Paper): 2018 = 1.731; WoS Impact Factor: 2018 = 4.026 (2) - 2018=4.022 (5)
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