Browsing by Author "Lu, DC"

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Analysis of evaporation of non-azeotropic refrigerants in a horizontal tube
(1996-10-01)
Chiou, CB
;
Lu, DC
;
Wang, CC
;
機械工程學系
;
Department of Mechanical Engineering
Based on the two-phase separated model, a detailed one-dimensional model for binary mixtures had been proposed to study the in-tube evaporation in a horizontal tube. The present model can predict the detailed variation of the composition, temperature, heat transfer rate and pressure drop of various binary mixtures under constant heat flux, counter-flow, or parallel-flow conditions. The predicted results agree favorably with the Takamatsu et al. [Int. J. Neat Mass Transfer 36, 3555-3563 (1993)] and Jung et al. [Exp. Heat Transfer 2, 237-255 (1989)] experimental data. Also, it is found that the full evaporation of the non-azeotropic refrigerants may require a corresponding temperature higher than the saturation temperature of the less volatile component. The non-linear variation of the property plays an important role in the heat transfer and pressure drop characteristics of the refrigerant mixtures. Copyright (C) 1996 Elsevier Science Ltd.
Characteristics of air-water two-phase flow in a 3-mm smooth tube
(2000-10-01)
Wang, CC
;
Yang, KS
;
Chang, YJ
;
Lu, DC
;
機械工程學系
Two-phase flow pattern and friction characteristics for an air-water system in a 3.17 mm smooth tube are reported in this study. The range of mass flux is between 50 and 700 kg/m(2)s. The experimental data show that the two-phase friction multipliers are strongly related to the flow pattern. For a stratified-wavy flow pattern, a mass-flux dependence of the two-phase multipliers is seen. For a non-stratified flow pattern, the two-phase frictional multipliers are comparatively independent of mass flux. Correlations of the frictional multipliers are developed for stratified and non-stratified flow. To use the appropriate correlation in different regime, a simple criterion is proposed.
Comprehensive study of convex-louver and wavy fin-and-tube heat exchangers
(1998-07-01)
Wang, CC
;
Tsai, YM
;
Lu, DC
;
機械工程學系
;
Department of Mechanical Engineering
A comprehensive study to investigate the heat transfer and friction characteristics of convex-louver and wavy fin-and-tube heat exchangers was carried out in this study. A total of 14 samples of heat exchangers, including seven convex-louver and seven wavy fin samples having identical waffle heights, were tested and compared in the present investigation. The effects of the number of tube row and fin pitch on the thermal-hydraulic characteristics were also reported. Results were presented as plots of Fanning friction factor f and the Colburn j factor against a Reynolds number based on a tube collar diameter in the range of 3 x 10(2) to 8 x 10(3).
Evaporation of R-22 in a 7-mm microfin tube
(1995)
Kuo, CS
;
Wang, CC
;
Cheng, WY
;
Lu, DC
;
機械工程學系
Investigations of pool boiling heat transfer of binary refrigerant mixtures
(1997-07-01)
Chiou, CB
;
Lu, DC
;
Wang, CC
;
機械工程學系
;
Department of Mechanical Engineering
Pool boiling data for binary mixtures of R-22/R-124 on plain tubes are reported at reduced pressures of 0.1, 0.15, and 0.2. Significant reductions of heat transfer coefficients for mixtures are found as compared to pure refrigerant, and the reduction of heat transfer coefficient is especially pronounced in the vicinity of the pore component. This phenomenon is strongly related to the nonlinear variation of physical properties of liquid viscosity and latent heat of the mixtures. The available empirical and semiempirical correlations developed for mixtures are compared with the present data. In addition, a correlation based on the present R-22/R-124 experimental data is proposed. This correlation not only predicts the deterioration of heat transfer coefficients for the present data with success but also predicts the experimental data from other investigators with reasonably good accuracy.
Investigations of pool boiling heat transfer of binary refrigerant mixtures
(1997-07-01)
Chiou, CB
;
Lu, DC
;
Wang, CC
;
機械工程學系
;
Department of Mechanical Engineering
Pool boiling data for binary mixtures of R-22/R-124 on plain tubes are reported at reduced pressures of 0.1, 0.15, and 0.2. Significant reductions of heat transfer coefficients for mixtures are found as compared to pure refrigerant, and the reduction of heat transfer coefficient is especially pronounced in the vicinity of the pore component. This phenomenon is strongly related to the nonlinear variation of physical properties of liquid viscosity and latent heat of the mixtures. The available empirical and semiempirical correlations developed for mixtures are compared with the present data. In addition, a correlation based on the present R-22/R-124 experimental data is proposed. This correlation not only predicts the deterioration of heat transfer coefficients for the present data with success but also predicts the experimental data from other investigators with reasonably good accuracy.
Pool boiling of R-22, R-124 and R-134a on a plain tube
(1997-05-01)
Chiou, CB
;
Lu, DC
;
Wang, CC
;
機械工程學系
;
Department of Mechanical Engineering
Pool boiling heat transfer on a plain tube having R-22, R-124 and R-134a as working fluids are reported in the present investigation. Experiments are conducted at saturation temperatures of 4.4 degrees C and 26.7 degrees C and at reduced pressures of 0.1 and 0.2. It is shown that the Cooper correlation can predict the present pool boiling heat transfer data satisfactorily. In addition, a semi-analytical prediction method is proposed in this study; this semi-analytical model can not only predict the present data with success, but also give reasonably good accuracy with the experimental data from other researchers. Copyright (C) 1996 Elsevier Science Ltd.
Pool boiling of R-22, R-124 and R-134a on a plain tube
(1997-05-01)
Chiou, CB
;
Lu, DC
;
Wang, CC
;
機械工程學系
;
Department of Mechanical Engineering
Pool boiling heat transfer on a plain tube having R-22, R-124 and R-134a as working fluids are reported in the present investigation. Experiments are conducted at saturation temperatures of 4.4 degrees C and 26.7 degrees C and at reduced pressures of 0.1 and 0.2. It is shown that the Cooper correlation can predict the present pool boiling heat transfer data satisfactorily. In addition, a semi-analytical prediction method is proposed in this study; this semi-analytical model can not only predict the present data with success, but also give reasonably good accuracy with the experimental data from other researchers. Copyright (C) 1996 Elsevier Science Ltd.
Single phase heat transfer and flow friction correlations for microfin tubes
(1996-10-01)
Wang, CC
;
Chiou, CB
;
Lu, DC
;
機械工程學系
;
Department of Mechanical Engineering
Single-phase heat transfer as well as pressure drop characteristics for microfin tubes with nominal diameter of 9.52, 7.94, and 7.0 mm are reported in the present investigation. In this study, seven commercially available microfin tubes and a smooth tube were tested using water as the test fluid. The heat transfer coefficients were obtained using the Wilson plot technique. It was found that the microfin tube exhibits a rough tube characteristics, and the enhancement levels increase with the Reynolds number and eventually reach a maximum value at a critical Reynolds number. The Dittus-Boelter type Wilson plot function cannot correlate the heat transfer data when the Reynolds number is less than the critical Reynolds number. Using the heat-momentum transfer analogy, a better correlation of the present mirocfin heat transfer data is achieved. In addition, the present correlations can predict 85.2% of the experimental data within 10% and 95.8% of the friction factor within 10%.
Single-phase heat transfer and pressure drop characteristics of microfin tubes
(1995)
Chiou, CB
;
Wang, CC
;
Lu, DC
;
機械工程學系
;
Department of Mechanical Engineering
Visual observation of two-phase flow pattern of R-22, R-134a, and R-407C in a 6.5-mm smooth tube
(1997-11-01)
Wang, CC
;
Chiang, CS
;
Lu, DC
;
機械工程學系
;
Department of Mechanical Engineering
Two-phase flow pattern and friction characteristics for R-22, R-134a, and R-407C inside a 6.5 mm smooth tube are reported in this study. The range of mass flux is between 50 and 700 kg/(m(2) s). The experimental data show that the two-phase friction multipliers are strongly related to the flow pattern. For a stratified, wavy flow pattern a mass-flux dependence of the multipliers is seen. The flow pattern transition for the mixture refrigerant shows a considerable delay, compared with that of pure refrigerant. (C) Elsevier Science Inc., 1997.