Prediction for Saturated Flow Boiling Heat Transfer in Mini-Channels

2013 ◽  
Author(s):  
Minxia Li ◽  
Chaobin Dang ◽  
Xing Fu ◽  
Yitai Ma
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Velocity Ratio ◽  
Heat Fluxes ◽  
Saturated Flow ◽  
Operation Conditions ◽  
Flow Boiling Heat Transfer ◽  
Wide Range ◽  
Mini Channels

A superposition correlation is proposed to predict heat transfer coefficient of flow boiling heat transfer in mini-channels. In this correlation, Reynolds number of liquid phase is presented by means of vapor velocity and slip velocity ratio. The film thickness and Bo number are taken account into this correlation. This new correlations were developed based on the conditions contained in our database. A database on experimental results of saturated-flow boiling in mini-channels includes 3839 data points, 9 different refrigerants, and covers a wide range of operation conditions from 10 independent studies. Most inner diameters in this database is within 0.5 mm and 3 mm and the mass fluxes in the database range from 50 to 600 kg /m2s, the heat fluxes from 5 to 123 kW/m2, the vapor qualities from 0 to 1, and the saturation temperatures from 0 to 52 °C. Research advances of flow boiling heat transfer in mini-channels in recent years were reviewed. 12 available flow boiling heat transfer correlations were addressed and evaluated against the database in this study. The proposed correlation can catch 77% data within the deviation of±30%. The mean absolute error of this new correlation is 20.9%.

Numerical Simulation of Saturated Flow Boiling Heat Transfer of Ammonia/Water Mixture in Bubble Pumps for Absorption–Diffusion Refrigerators

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
Soo W. Jo ◽  
S. A. Sherif ◽  
W. E. Lear
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Water Mixture ◽  
Saturated Flow ◽  
Ammonia Water ◽  
Flow Boiling Heat Transfer ◽  
Bubble Pump

This paper addresses a multidimensional numerical simulation of the saturated flow boiling heat transfer in bubble pumps of absorption–diffusion refrigeration cycles. The bubble pump with a shape of vertical tube is subjected to a uniform heat flux from the tube outer wall surface along the entire pump length. As the bubble pump wall is heated, a nonazeotropic mixture of saturated strong ammonia/water entering into the bubble pump transforms to ammonia vapor and diluted ammonia/water mixture. The weaker ammonia/water mixture is lifted by the buoyant force created by the ammonia vapor. The present multidimensional numerical simulation was performed using the two-fluid model with the equilibrium phase change model and the standard k-ε turbulence model. The numerical model designed for the present simulation was validated through a comparative study referring to available experimental data. The present numerical model was compared with the one-dimensional model to assess its applicability for numerical simulation of the saturated flow boiling heat transfer in bubble pumps. As a result, it is seen that the present numerical model predicts the performance of ammonia/water bubble pumps more realistically than the one-dimensional model. In addition, the effects of the bubble pump's geometrical dimension and heat input on the pump performance were investigated using the present numerical approach.

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