A Semi-Empirical Model for Condensation Heat Transfer Coefficient of Mixed Ethanol-Water Vapors

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Yang Li ◽  
JunJie Yan ◽  
JinShi Wang ◽  
GuoXiang Wang
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Empirical Model ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics ◽  
Semi Empirical

A semi-empirical model describing the heat transfer characteristics of the pseudo-dropwise condensation of binary vapor on a cooled vertical tube has been formulated. By ignoring the thin film always present on the condensation surface and the intensification of mass transfer caused by the Marangoni effect, the heat transfer characteristics of pseudo-dropwise condensation are tentatively formulated. The model involved an analysis of the diffusion process in the vapor boundary layer along with the heat transfer process through the condensate drops. This model was applied to the condensation of the saturated binary vapor of ethanol and water, and was examined using experimental data at vapor pressure values of 101.33 kPa (provided by Utaka and Wang, 2004, “Characteristic Curves and the Promotion Effect of Ethanol Addition on Steam Condensation Heat Transfer,” Int. J. Heat Mass Transfer, 47, pp. 4507–4516), 84.52 kPa and 47.36 kPa. Calculations using the model show a similar trend to the experimental measurements. With the change of the vapor-to-surface temperature difference, the heat transfer coefficients revealed nonlinear characteristics, with the peak values under all ethanol mass fractions of binary vapor. The heat transfer coefficients increased with decreasing ethanol mass fraction.

scholarly journals Heat Transfer Characteristics of Aluminum Sputtered Fabrics

2018 ◽  
Vol 13 (3) ◽  
pp. 155892501801300 ◽  
Author(s):  
Hye Ree Han ◽  
Yaewon Park ◽  
Changsang Yun ◽  
Chung Hee Park
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Ambient Air ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Hot Plate ◽  
Multilayer Systems ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics ◽  
Shape Memory Polyurethane

Al was sputtered onto four substrates: nylon, polyester, cotton/polyester, and shape memory polyurethane nanoweb, and the heat-transfer characteristics of the resultant materials were investigated by surface temperature measurements. The thickness of the Al layer increased linearly with sputtering time. The heat-transfer mechanisms of the multilayer systems in terms of conduction, convection, and radiation were investigated under steady-state conditions using a hot plate as a heat source in contact with Al-sputtered fabrics. The Al-sputtered fabric was placed on the hot plate, which was maintained at 35°C, and exposed to open air, which was maintained at 15°C. The temperatures of the air-facing surfaces of hot plate-Al-fabric-air (i.e., Al-phase-down) and hot plate-fabric-Al-air (i.e., Al-phase-up) systems were used to investigate the heat-transfer mechanism. It was found that heat dissipation to ambient air was much higher for the Al-phase-up system than for the Al-phase-down system. Heat-transfer coefficients of the Al surfaces were calculated and found to increase with the thickness of the Al layer. Furthermore, different conductive thermal resistances were observed for different fabrics prepared with the same Al-sputtering time. Consequently, differences in their thicknesses pore sizes, and thermal conductivities were suggested to have significant effects on their heat-transfer properties.

Heat Transfer Characteristics of Impinging Two-Dimensional Air Jets

1966 ◽  
Vol 88 (1) ◽  
pp. 101-107 ◽  
Author(s):  
Robert Gardon ◽  
J. Cahit Akfirat
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics ◽  
Air Jets

Local as well as average heat transfer coefficients between an isothermal flat plate and impinging two-dimensional jets were measured for both single jets and arrays of jets. For a large and technologically important range of variables the results have been correlated in relatively simple terms, and their application to design is briefly considered.

Study on Condensation Heat Transfer on Micro Structured Surfaces (Effect on Condensation Heat Transfer of Metal Sputtering Surfaces)

2013 ◽  
Author(s):  
Kohei Yamazaki ◽  
Hiroyasu Ohtake ◽  
Koji Hasegawa
Keyword(s):  
Heat Transfer ◽  
Metal Film ◽  
Copper Surface ◽  
Thin Metal Film ◽  
Thin Metal ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Transfer Coefficients ◽  
Structured Surfaces ◽  
Heat Transfer Coefficients

The present study was intended to examine how the condensation heat transfer, especially the dropwise condensation, was affected by modifying the surface nature. In the present study, condensation heat transfer experiments for steam were performed by using mirror-finished copper surface and some very thin metal-film surfaces by using sputtering on mirror-finished copper block. That is, the effects on pattern of condensation heat transfer, i.e., dropwise or film-wise condensation, of metal-sputtered surfaces were examined experimentally and qualitatively. The present experimental results showed that the condensation on sputtered metal surfaces of Copper (Cu), Chromium (Cr) and Lead (Pb), became dropwise condensation. The heat transfer coefficients were ten times higher than the Nusselt equation. The condensation on sputtered metal surface of Titanium (Ti) became filmwise condensation. High contact angle was trended to be dropwise condensation on very thin metal-film surfaces by using sputtering.

Experimental Investigation on Heat Transfer Characteristics of Supercritical Carbon Dioxide Inside a Horizontal Micro-Fin Copper Tube During Cooling Process

2007 ◽  
Author(s):  
Shinya Higahiiue ◽  
Ken Kuwahara ◽  
Satoru Yanachi ◽  
Shigeru Koyama
Keyword(s):  
Heat Transfer ◽  
Mass Velocity ◽  
Expansion Ratio ◽  
Test Tube ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics ◽  
Inner Diameter ◽  
Fin Tube

Experimental study on cooling heat transfer of CO2 and CO2-PAG mixture flowing in a horizontal micro-fin tube under the supercritical pressure conditions was performed. The test tube having the average inner diameter of 4.76 mm, the fin height of 0.245 mm, the number of fins of 50, the area expansion ratio of 2.08 was conducted in this study. The microfins of the test tube were treated in straight along the axes of the tube on the heat transfer surface. The heat transfer coefficients of pure CO2 were measured at conditions of 8 and 10 MPa in pressure and 340 – 660 kg/(m2 s) in mass velocity. The measured heat transfer coefficients of the micro-fin tube showed 1.7 times higher than that of smooth tube with 4.42 mm inner diameter. The effect of PAG on heat transfer characteristics were investigated experimentally at 10 MPa in pressure, 510 kg/(m2 s) in mass velocity and 0.06 to 2.26% in the mass percent concentration of PAG in CO2-PAG mixture. The measured heat transfer coefficients of CO2 -PAG mixture decreased about 50% as compared with that of pure CO2 at the pseudocritical temperature.

Flow Boiling Heat Transfer of R123/R134a Mixture in a Micro-Channel

2010 ◽  
Author(s):  
Sehwan In ◽  
Sangkwon Jeong
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Micro Channel ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics ◽  
Flow Boiling Heat Transfer ◽  
Micro Channels

This paper describes the flow boiling heat transfer of R123/R134a mixture in a single round micro-channel with 0.19 mm ID. The flow boiling heat transfer coefficients were measured with the variation of mixture composition (R123 mole fraction: 0.502, 0.746) at various experimental conditions: mass velocities (314, 392, 470 kg/m2-s), heat fluxes (10, 15, 20 kW/m2) and vapor qualities (0.2–0.85). The heat transfer characteristics of R123/R134a mixture are similar to those of pure R123 observed in the previous flow boiling experiment. The similarity of heat transfer characteristics denotes that the heat transfer is governed by evaporation of thin liquid film around the elongated bubbles like the case of pure R123. The heat transfer coefficients of R123/R134a mixture are compared with those of equivalent pure refrigerant by the correlation developed from pure R123 experimental results. The large reduction of heat transfer coefficients compared with pure refrigerant is found in micro-channels flow boiling by the mass transfer effect of mixed refrigerant. In addition, macro-channel correlations for mixed refrigerant do not make accurate prediction about the reduction of heat transfer coefficients.

Mechanism and Condensation Heat Transfer Characteristics Research on the Depth of the Flue Gas Heat Recovery from Burning Natural Gas

2014 ◽  
Vol 687-691 ◽  
pp. 637-640
Author(s):  
Jian Wei Han ◽  
Wei Lv ◽  
Jian Min Gao ◽  
Qian Du ◽  
Chao Cheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Gas ◽  
Flue Gas ◽  
Heat Recovery ◽  
Cooling Water ◽  
Dew Point ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

This article probe into the depth of the flue gas heat recovery from the burning of natural gas. It explore the mechanism of the way to control the temperature of the flue gas from the burning of natural gas below the dew point temperature. It expounds the absorption way of sensible heat and latent heat from the vaporization in flue gas. After the study on the condensation heat transfer characteristics of the flue gas from the burning of natural gas, we can find that the dropwise condensation is more conducive to the heat exchange between flue gas and cooling water. And to find the method of dropwise condensation.

Effect of Outflow Orientation on Heat Transfer and Pressure Drop in a Triangular Duct With an Array of Tangential Jets

2000 ◽  
Vol 122 (4) ◽  
pp. 669-678 ◽  
Author(s):  
J.-J. Hwang ◽  
B.-Y. Chang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Loss Coefficient ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics

Experiments are conducted to study the heat transfer and pressure drop characteristics in a triangular duct cooled by an array of tangential jets, simulating the leading-edge cooling circuit of a turbine blade. Coolant ejected from a high-pressure plenum through an array of orifices is aimed at the leading-edge apex and exits from the radial outlets. Three different outflow orientations, namely coincident with the entry flow, opposed to the entry flow, and both, are tested for various Reynolds numbers 12600⩽Re⩽42000. A transient liquid crystal technique is used to measure the detailed heat transfer coefficients on two walls forming the leading-edge apex. Flow rate across each jet hole and the crossflow development, which are closely related to the local heat transfer characteristics, are also measured. Results show that increasing Re increases the heat transfer on both walls. The outflow orientation affects significantly the local heat transfer characteristics through influencing the jet flow together with the crossflow in the triangular duct. The triangular duct with two openings is recommended since it has the highest wall-averaged heat transfer and the moderate loss coefficient among the three outflow orientations investigated. Correlations for wall-averaged Nusselt number and loss coefficient in the triangular duct have been developed by considering the Reynolds number for three different outflow orientations. [S0022-1481(00)01204-4]

Study on Condensation Heat Transfer Characteristics of Nonazeotropic Binary Refrigerant Mixture R1234yf/R32 Inside Small-Scale Horizontal Smooth Tubes

2013 ◽  
Author(s):  
Linlin Wang ◽  
Chaobin Dang ◽  
Eiji Hihara
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Small Scale ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Refrigerant Mixture ◽  
Mass Fluxes ◽  
Binary Refrigerant

In this study, condensation heat transfer characteristics of nonazeotropic mixtures R1234yf and R32 (mass fractions of 0.52:0.48 and 0.77:0.23, respectively) inside a horizontal smooth tube (inner diameter 2 mm) were experimentally investigated at mass fluxes ranging from 100 to 400 kg/m2 s and at a saturation temperature of 40 °C. A prediction model using a modified heat transfer correlation for pure refrigerant was constructed, the details of which are presented here. The heat transfer characteristics, especially the heat transfer deterioration caused by the mass transfer difference of the nonazeotropic refrigerant mixture, were evaluated by combining the correlations of heat transfer and mass transfer on both the vapor side and the liquid side. Through comparison with experimental data, the obtained prediction results were found to agree reasonably with the experimental condensation heat transfer coefficient of binary refrigerant mixtures using R1234yf and R32.

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