A numerical model for boiling heat transfer coefficient of zeotropic mixtures

Cryogenic Engineering Conference 2017

材料科学;物理学

Vicencio, Rodrigo Barraza^1 ; Aedo, Eduardo Caviedes^1

Department of Mechanical Engineering, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso, Chile^1

关键词: Boiling heat-transfer coefficients;    Convective heat transfer Coefficient;    Flow and heat transfer;    Heat exchangers designs;    Liquid vapor equilibrium;    Local heat transfer coefficient;    Temperature profiles;    Two phase annular flow;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/278/1/012062/pdf
DOI  :  10.1088/1757-899X/278/1/012062

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

Zeotropic mixtures never have the same liquid and vapor composition in the liquid-vapor equilibrium. Also, the bubble and the dew point are separated; this gap is called glide temperature (Tglide). Those characteristics have made these mixtures suitable for cryogenics Joule-Thomson (JT) refrigeration cycles. Zeotropic mixtures as working fluid in JT cycles improve their performance in an order of magnitude. Optimization of JT cycles have earned substantial importance for cryogenics applications (e.g, gas liquefaction, cryosurgery probes, cooling of infrared sensors, cryopreservation, and biomedical samples). Heat exchangers design on those cycles is a critical point; consequently, heat transfer coefficient and pressure drop of two-phase zeotropic mixtures are relevant. In this work, it will be applied a methodology in order to calculate the local convective heat transfer coefficients based on the law of the wall approach for turbulent flows. The flow and heat transfer characteristics of zeotropic mixtures in a heated horizontal tube are investigated numerically. The temperature profile and heat transfer coefficient for zeotropic mixtures of different bulk compositions are analysed. The numerical model has been developed and locally applied in a fully developed, constant temperature wall, and two-phase annular flow in a duct. Numerical results have been obtained using this model taking into account continuity, momentum, and energy equations. Local heat transfer coefficient results are compared with available experimental data published by Barraza et al. (2016), and they have shown good agreement.