{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T00:58:03Z","timestamp":1791507483869,"version":"4.3.4"},"reference-count":23,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2015,4,22]],"date-time":"2015-04-22T00:00:00Z","timestamp":1429660800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Four different double-compression CO2 transcritical refrigeration cycles are studied: double-compression external intercooler cycle (DCEI), double-compression external intercooler cycle with an expander (DCEIE), double-compression flash intercooler cycle (DCFI), double-compression flash intercooler cycle with an expander (DCFIE). The results showed that the optimum gas cooler pressure and optimum intermediate pressure of the flash intercooler cycles are lower than that of the external intercooler cycle. The use of an expander in the DCEI cycle leads to a decrease of the optimum gas cooler pressure and little variation of the optimum intermediate pressure. However, the replacement of the throttle valve with an expander in the DCFI cycle results in little variation of the optimal gas cooler pressure and an increase of the optimum intermediate pressure. The DCFI cycle outperforms the DCEI cycle under all the chosen operating conditions. The DCEIE cycle outperforms the DCFIE cycle when the evaporating temperature exceeds 0 \u00b0C or the gas cooler outlet temperature surpasses 35 \u00b0C. When the gas cooler exit temperature varies from 32 \u00b0C to 48 \u00b0C, the DCEI cycle, DCEIE cycle, DCFI cycle and DCFIE cycle yield averaged 4.6%, 29.2%, 12.9% and 22.3% COP improvement, respectively, over the basic cycle.<\/jats:p>","DOI":"10.3390\/e17042544","type":"journal-article","created":{"date-parts":[[2015,4,22]],"date-time":"2015-04-22T12:14:23Z","timestamp":1429704863000},"page":"2544-2555","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["Thermodynamic Analysis of Double-Stage Compression Transcritical CO2 Refrigeration Cycles with an Expander"],"prefix":"10.3390","volume":"17","author":[{"given":"Zhenying","family":"Zhang","sequence":"first","affiliation":[{"name":"Institute of Architecture and Civil Engineering, North China University of Science and Technology, Tangshan 063009, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lirui","family":"Tong","sequence":"additional","affiliation":[{"name":"Institute of Architecture and Civil Engineering, North China University of Science and Technology, Tangshan 063009, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xingguo","family":"Wang","sequence":"additional","affiliation":[{"name":"Institute of Architecture and Civil Engineering, North China University of Science and Technology, Tangshan 063009, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2015,4,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1006","DOI":"10.1016\/j.ijrefrig.2007.12.016","article-title":"An experimental evaluation of the transcritical CO2 refrigerator performances using an internal heat exchanger","volume":"31","author":"Aprea","year":"2008","journal-title":"Int. J. Refrig."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1016\/j.enconman.2009.08.024","article-title":"Experimental study on the performance of CO2 residential air-conditioning system with an internal heat exchanger","volume":"51","author":"Tao","year":"2010","journal-title":"Energy Convers. Manag."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.ijrefrig.2010.07.006","article-title":"Energetic evaluation of an internal heat exchanger in a CO2 transcritical refrigeration plant using experimental data","volume":"34","author":"Torrella","year":"2011","journal-title":"Int. J. Refrig."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1274","DOI":"10.1016\/j.ijrefrig.2005.09.004","article-title":"Two-stage transcritical carbon dioxide cycle optimisation: A theoretical and experimental analysis","volume":"28","author":"Cavallini","year":"2005","journal-title":"Int. J. Refrig."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1058","DOI":"10.1016\/j.ijrefrig.2008.10.001","article-title":"Thermodynamic analysis of different two-stage transcritical carbon dioxide cycles","volume":"32","author":"Cecchinato","year":"2009","journal-title":"Int. J. Refrig."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"376","DOI":"10.1080\/10789669.2013.784644","article-title":"Recent advances of energy recovery expanders in the transcritical CO2 refrigeration cycle","volume":"19","author":"Zhang","year":"2013","journal-title":"HVAC&R Res."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"4013","DOI":"10.1016\/j.rser.2011.07.021","article-title":"Transcritical carbon dioxide heat pump systems: A review","volume":"15","author":"Austin","year":"2011","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.ijrefrig.2008.07.008","article-title":"Performance evaluation of a two-stage CO2 cycle with gas injection in the cooling mode operation","volume":"32","author":"Cho","year":"2009","journal-title":"Int. J. Refrig."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1485","DOI":"10.1016\/j.applthermaleng.2008.06.030","article-title":"Numerical evaluation on the performance of advanced CO2 cycles in the cooling mode operation","volume":"29","author":"Cho","year":"2009","journal-title":"Appl. Therm. Eng."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2819","DOI":"10.1016\/j.enconman.2011.02.003","article-title":"Theoretical analysis and experimental research on transcritical CO2 two stage compression cycle with two gas coolers (TSCC + TG) and the cycle with intercooler (TSCC + IC)","volume":"52","author":"Wang","year":"2011","journal-title":"Energy Convers. Manag."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1162","DOI":"10.1016\/j.energy.2004.08.007","article-title":"Exergy analysis of transcritical carbon dioxide refrigeration cycle with an expander","volume":"30","author":"Yang","year":"2005","journal-title":"Energy"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"141","DOI":"10.1016\/j.ijrefrig.2004.08.006","article-title":"Piston-cylinder work producing expansion device in a transcritical carbon dioxide cycle. Part I: Experimental investigation","volume":"28","author":"Baek","year":"2005","journal-title":"Int. J. Refrig."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"152","DOI":"10.1016\/j.ijrefrig.2004.08.007","article-title":"Piston-cylinder work producing expansion device in a transcritical carbon dioxide cycle. Part II: Theoretical model","volume":"28","author":"Baek","year":"2005","journal-title":"Int. J. Refrig."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"729","DOI":"10.1080\/10789669.2009.10390860","article-title":"A rolling piston-type two-phase expander in the transcritical CO2 cycle","volume":"15","author":"Li","year":"2009","journal-title":"HVAC&R Res"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"732","DOI":"10.1016\/j.ijrefrig.2010.12.005","article-title":"Improved rotary vane expander for trans-critical CO2 cycle by introducing high-pressure gas into the vane slots","volume":"34","author":"Jia","year":"2011","journal-title":"Int. J. Refrig."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1243\/095440805X7080","article-title":"Theoretical performance of transcritical carbon dioxide cycle with two-stage compression and intercooling","volume":"219","author":"Baek","year":"2005","journal-title":"Proc. Inst. Mech. Eng. E J. Process Mech. Eng."},{"key":"ref_17","unstructured":"Kohsokabe, H., Funakoshi, S., Tojo, K., Nakayama, S., Kohno, K., and Kurashige, K. (2006, January 15\u201320). Basic operating characteristics of CO2 refrigeration cycles with expander-compressor unit, West Lafayette, IN, USA."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1654","DOI":"10.1016\/j.applthermaleng.2007.11.002","article-title":"Numerical simulation on scroll expander\u2014Compressor unit for CO2 trans-critical cycles","volume":"28","author":"Kim","year":"2008","journal-title":"Appl. Therm. Eng."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/j.energy.2013.06.042","article-title":"Performance study of a transcritical carbon dioxide cycle with an expressor","volume":"60","author":"Zhili","year":"2013","journal-title":"Energy"},{"key":"ref_20","unstructured":"Lemmon, E., Huber, M., and McLinden, M. (2007). NIST Reference Fluid Thermodynamic and Transport Properties\u2014REFPROP version 8.0, National Institute of Standards and Technology."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"831","DOI":"10.1016\/S1359-4311(99)00070-8","article-title":"A correlation of optimal heat rejection pressures in transcritical carbon dioxide cycles","volume":"20","author":"Liao","year":"2000","journal-title":"Appl. Therm. Eng."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1016\/j.energy.2006.03.031","article-title":"Performance investigation of transcritical carbon dioxide two-stage compression cycle with expander","volume":"32","author":"Yang","year":"2007","journal-title":"Energy"},{"key":"ref_23","first-page":"1","article-title":"Study of N2O transcritical two stage compression expander refrigeration cycle","volume":"6","author":"Qian","year":"2009","journal-title":"Cryogenics"}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/17\/4\/2544\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T20:45:09Z","timestamp":1760215509000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/17\/4\/2544"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,4,22]]},"references-count":23,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2015,4]]}},"alternative-id":["e17042544"],"URL":"https:\/\/doi.org\/10.3390\/e17042544","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2015,4,22]]}}}