Thermodynamic analysis of the optimal operating conditions for a two-stage CO2 refrigeration unit in warm climates with and without ejector
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Other documents of the author: Expósito Carrillo, José Antonio; Sánchez de la Flor, Francisco José; PERIS PEREZ, BERNARDO; Salmerón Lissen, José Manuel
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https://doi.org/10.1016/j.applthermaleng.2020.116284 |
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Title
Thermodynamic analysis of the optimal operating conditions for a two-stage CO2 refrigeration unit in warm climates with and without ejectorAuthor (s)
Date
2021-02-25Publisher
ElsevierISSN
1359-4311Bibliographic citation
EXPÓSITO-CARRILLO, José Antonio, et al. Thermodynamic analysis of the optimal operating conditions for a two-stage CO2 refrigeration unit in warm climates with and without ejector. Applied Thermal Engineering, 2021, vol. 185, p. 116284Type
info:eu-repo/semantics/articlePublisher version
https://www.sciencedirect.com/science/article/pii/S1359431120337637Version
info:eu-repo/semantics/publishedVersionSubject
Abstract
The natural refrigerant R744 seems to be the long term solution to be imposed in the food retail industry, where low and medium refrigeration temperatures are usually required, despite the technical difficulties related ... [+]
The natural refrigerant R744 seems to be the long term solution to be imposed in the food retail industry, where low and medium refrigeration temperatures are usually required, despite the technical difficulties related to high the pressure, especially in warm climates, leading to trans-critical operation with the consequent COP reduction. To overcome such difficulties, different approaches have been proposed in literature, being very popular the use of parallel compressor or its combination with ejector expansion devices. The efficient operation of trans-critical R744 systems requires the control of the gas cooler pressure, as well as the pressure of the flash-tank. In the case of ejector expansion devices, the ratio of entrained mass flow rate must be also included in the control variables and, at the same time, its use implies additional restrictions. The current paper presents the optimization methodology for the operating conditions of a two-stage CO2 refrigeration unit for both cases, with and without ejector. The curves of optimal combinations of gas cooler and flash-tank pressures, understood as operational control laws, are provided together with the COP achieved. The operating conditions and performance of the ejector case are compared showing COP improvements of up to 13%. The results also show that the operating region of the control variables is limited due to the use of the ejector. [-]
Is part of
Applied Thermal Engineering, 2021, vol. 185Funder Name
European Regional Development Fund
Project code
ITC-20181143
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