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Multi-evaporator Joule-Thomson cryogenic refrigeration cycles created by pumping and suction mechanisms

Rostamzadeh, H ; Sharif University of Technology | 2020

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  1. Type of Document: Article
  2. DOI: 10.1016/j.applthermaleng.2020.115367
  3. Publisher: Elsevier Ltd , 2020
  4. Abstract:
  5. Due to the simple structure and low production cost of Joule-Thomson (JT) refrigeration cycles, these cryogenic systems have widely been used in many food or medicine industries. However, in many scenarios, two or even three cryogenic temperatures are needed to simultaneously supply different cryogenic cooling loads since each product has its own comfort low-temperature range. In this case, multi-evaporator JT systems can be a promising solution to address several cryogenic temperatures via employing different evaporators. Following this objective, an innovative triple-evaporator JT cycle is proposed, where the pressure difference between evaporators is created via a pumping mechanism by employing two vacuum pumps between the evaporators. In order to enhance the overall performance of this pumping-based triple-evaporator JT system, the two vacuum pumps are replaced by two ejectors and it is called the suction-based triple-evaporator JT cycle. To address the unbalanced term in energy equation of the internal heat exchanger due to the high temperature difference between the heat source and heat sink, an ejector expander JT cycle is used as a precooling cycle. Using nitrogen as working fluid, the performance of the proposed triple-evaporator JT systems is evaluated from the first and second laws of thermodynamics standpoints. Genetic algorithm method is used to optimize performance of the two proposed systems and the results are compared with each other. It is found that the optimum coefficient of performance (COP) and exergy efficiency of the suction-based triple-evaporator JT cycle are around 107% and 92% higher than those of the pumping-based triple-evaporator JT cycle, respectively. The optimum cooling load, total consumed electricity, COP, and exergy efficiency are computed 22.1 kW, 1523 kW, 0.0145, and 2.7% (for the pumping-based triple-evaporator JT cycle) and 24.94 kW, 828.2 kW, 0.0301, and 5.2% (for the suction-based triple-evaporator JT cycle), respectively. © 2020 Elsevier Ltd
  6. Keywords:
  7. Ejector ; Joule-Thomson cycle ; Optimization ; Pumping mechanism ; Suction mechanism ; Triple-evaporator ; Air conditioning ; Costs ; Cryogenics ; Ejectors (pumps) ; Exergy ; Genetic algorithms ; Refrigeration ; Temperature ; Thermoelectricity ; Vacuum pumps ; Coefficient of performances (COP) ; Cryogenic refrigeration ; Cryogenic temperatures ; Exergy efficiencies ; Internal heat exchanger ; Pressure differences ; Refrigeration cycles ; Second laws of thermodynamics ; Evaporators
  8. Source: Applied Thermal Engineering ; Volume 175 , 2020
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S1359431120301344