Numerical simulation of tubes-in-tube heat exchanger in a mixed refrigerant Joule_Thomson cryocooler

26th International Cryogenic Engineering Conference & International Cryogenic Materials Conference 2016

材料科学;物理学

Damle, R.M.^1 ; Ardhapurkar, P.M.^2 ; Atrey, M.D.^1

Department of Mechanical Engineering, IIT Bombay, Mumbai

400076, India^1

S.S.G.M College of Engineering, Shegaon

444203, India^2

关键词: Boiling and condensations;    Cryogenic temperatures;    Non-azeotropic mixture;    Recuperative heat exchangers;    Temperature conditions;    Transient formulations;    Tube-in-tube heat exchanger;    Two-phase heat transfer;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/171/1/012070/pdf
DOI  :  10.1088/1757-899X/171/1/012070

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

Mixed refrigerant Joule-Thomson (MRJT) cryocoolers can produce cryogenic temperatures with high efficiency and low operating pressures. As compared to the high system pressures of around 150-200 bar with nitrogen, the operational pressures with non-azeotropic mixtures (e.g., nitrogen-hydrocarbons) come down to 10-25 bar. With mixtures, the heat transfer in the recuperative heat exchanger takes place in the two-phase region. The simultaneous boiling and condensation of the cold and hot gas streams lead to higher heat transfer coefficients as compared to single phase heat exchange. The two-phase heat transfer in the recuperative heat exchanger drastically affects the performance of a MRJT cryocooler. In this work, a previously reported numerical model for a simple tube-in-tube heat exchanger is extended to a multi tubes-in-tube heat exchanger with a transient formulation. Additionally, the J-T expansion process is also considered to simulate the cooling process of the heat exchanger from ambient temperature conditions. A tubes-in-tube heat exchanger offers more heat transfer area per unit volume resulting in a compact design. Also, the division of flow in multiple tubes reduces the pressure drop in the heat exchanger. Simulations with different mixtures of nitrogen-hydrocarbons are carried out and the numerical results are compared with the experimental data.