The Infrared Characteristics of the Wall Temperature of Boiling Heat Transfer in Microchannel

2011 ◽  
Vol 383-390 ◽  
pp. 811-815
Author(s):  
Hu Gen Ma ◽  
Jian Mei Bai ◽  
Rong Jian Xie ◽  
Wen Jing Tu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Temperature ◽  
Boiling Heat Transfer ◽  
Transfer Test ◽  
Axial Direction ◽  
Transfer Model ◽  
Micro Channel ◽  
Vapor Quality ◽  
Test Rig

In this paper, the boiling heat transfer test rig was designed and built, while the characteristics of boiling Heat Transfer of refrigerants in micro-channel was researched. The wall temperature of micro-channel was measured by TH5104 Infrared thermography. The results showed that there were obvious variations for wall temperature of micro-channel along the axial direction when boiling heat transfer occurred in the micro-channel. The temperature distribution affected obviously by the heat flux, mass flow rate; vapor quality and heat transfer model.

Flow Boiling Heat Transfer of R-22 in Small-Diameter Horizontal Round Tubes

2003 ◽  
Author(s):  
K. S. Park ◽  
W. H. Choo ◽  
K. H. Bang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Vapor Quality ◽  
Flow Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient

The flow boiling heat transfer coefficient of R-22 in small hydraulic diameter tubes has been experimentally studied. Both brass and aluminum round tubes of 1.66 mm inside diameter are used for the test section. The ranges of the major experimental parameters are 300∼600 kg/m2s of refrigerant mass flux, 10∼20 kW/m2 of the wall heat flux, 0.0∼0.9 of the inlet vapor quality. The experimental result showed that the flow boiling heat transfer coefficient in this small tubes are in the range of 2∼4 kW/m2K and it varies only by heat flux, independent of mass flux and vapor quality. It is also observed that the heat transfer coefficients in the aluminum tube are up to 50% higher than in the brass tube.

Experimental Study on Heat Transfer Characteristics of Water and Ethanol Flow Boiling in Micro-Channel

2013 ◽  
Vol 330 ◽  
pp. 788-791
Author(s):  
Xia Weng ◽  
Dong Yao Liu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Bond Number ◽  
Micro Channel ◽  
Vapor Quality ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

The Heat transfer characteristics of water and ethanol flow boiling in micro-channel are studied. Flow boiling of different mass and heat flux is carried out in 61 parallel microchannel with hydro diameter of 0.293mm, and the local heat transfer coefficient (HTC) of is calculated. The results indicate that the HTC decreases with the increasing of vapor quality, and depends on heat flux. Two latest correlations are used to predict the experiment, and the results indicate that the Bond number plays an important role in the correlation.

Effect of saturation temperature and vapor quality on the boiling heat transfer and critical heat flux in a microchannel

2020 ◽  
Vol 117 ◽  
pp. 104768
Author(s):  
Ahmet Selim Dalkılıç ◽  
Ali Celen ◽  
Murat Erdoğan ◽  
Kittipong Sakamatapan ◽  
Kazi Salim Newaz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Saturation Temperature ◽  
Vapor Quality

scholarly journals Experimental Approaches to Measurement of Vapor Quality of Two-Phase Flow Boiling

2020 ◽  
Author(s):  
Mehdi Kabirnajafi ◽  
Jiajun Xu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Phase Flow ◽  
Vapor Quality ◽  
Two Phase ◽  
Thermal Boundary Conditions ◽  
Flow Boiling Heat Transfer ◽  
Experimental Approaches

Vapor quality is one of the crucial parameters substantially affecting the flow boiling heat transfer coefficient. Hence, the reliability and accuracy of vapor quality measurements is of a great significance to accurately investigating the effect of vapor quality on the local flow boiling heat transfer coefficients. In the present study, various experimental approaches are represented to measure and control local vapor quality for flow boiling tests. Experimental approaches are classified based on the type of thermal boundary conditions imposed on the tube wall, that is, known constant wall heat flux and constant wall temperature (unknown variable wall heat flux). In addition, in-situ techniques are also investigated to measure local vapor quality regardless of the governing thermal boundary conditions within two-phase flow experiments. Finally, the experimental methodologies are compared based on their level of reliability and accuracy in measurement, costliness and affordability, and simplicity in execution to address their potential merits and demerits.

Comparison and Improvements of Correlations for Film Boiling in Tubes

2009 ◽  
Author(s):  
E.-L. Pelletier ◽  
L. K. H. Leung ◽  
A. Teyssedou ◽  
R. Girard
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Boiling Heat Transfer ◽  
Prediction Accuracy ◽  
Film Boiling ◽  
Independent Parameter ◽  
Maximum Temperature

Two methodologies to predict film boiling heat-transfer coefficient have been assessed against experimental wall-temperature measurements obtained under steady-state conditions with water flow inside vertical tubes. One of these methodologies employs heat flux as the independent parameter while the other uses wall temperature as the independent parameter. The film boiling heat transfer consists of developing and fully developed film-boiling regions. Film boiling heat-transfer coefficients are predicted using the film boiling look-up tables for fully developed flow. Developing film-boiling effect is accounted for using modification factors to the fully developed heat-transfer coefficient. Wall-temperature distributions along uniformly heated tubes were established using a semi-analytical scheme and compared against measurements. Both methodologies have provided good predictions. However, the overall prediction accuracy for the heat-flux-based correlation is slightly better than that for the wall-temperature-based correlation. Wall temperatures predicted with the heat-flux-based correlation follow closely measurements at the developing post-dryout region. The wall superheat correlation predicts a sharp temperature rise once the critical heat flux is exceeded, resulting in discrepancies between predictions and measurements of wall temperature and overpredictions of the maximum temperature. The wall-temperature-based modification factor for the developing film-boiling region has been revised using the tube heat-transfer database to improve the prediction accuracy of the wall temperature.

Cryogenic Chilldown Model for Stratified Flow Inside a Pipe

2005 ◽  
Author(s):  
Jun Liao ◽  
Kun Yuan ◽  
Renwei Mei ◽  
James F. Klausner ◽  
Jacob Chung
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Boiling Heat Transfer ◽  
Pipe Wall ◽  
Computational Cost ◽  
Stratified Flow ◽  
Nucleate Boiling ◽  
Transfer Model ◽  
Two Phase ◽  
Horizontal Pipe

A pseudo-steady model has been developed to predict the chilldown history of the pipe wall temperature in horizontal transport pipelines for cryogenic fluids. A new film boiling heat transfer model is developed by incorporating the stratified flow structure for cryogenic chilldown. A modified nucleate boiling heat transfer correlation for the cryogenic chilldown process inside a horizontal pipe is proposed. The efficacy of the correlations is assessed by comparing the model predictions with measured values of wall temperature in several azimuthal positions in a well controlled experiment by Chung et al. (2004). The computed pipe wall temperature histories match well with the measured results. The present model captures important features of thermal interaction between the pipe wall and the cryogenic fluid, provides a simple and robust platform for predicting the pipe wall chilldown history in a long horizontal pipe at relatively low computational cost, and builds a foundation to incorporate the two-phase hydrodynamic interaction in the chilldown process.

Flow Boiling in Minichannels of Copper, Brass, and Aluminum Round Tubes

2004 ◽  
Author(s):  
K. H. Bang ◽  
W. H. Choo
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Wall Heat Flux ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Flow Boiling Heat Transfer

The past work on flow boiling heat transfer in minichannels ranging one to three millimeters of hydraulic diameter has indicated that the local heat transfer coefficients are largely independent of mass flux and vapor quality, but mainly a function of wall heat flux. The present work is a revisit of flow boiling in minichannels by conducting experiment using 1.67 mm inner diameter tubes of three different materials; aluminum, brass, and copper, to investigate an effect of the tube inner surface conditions with the focus on an effect on nucleate boiling. Tests were conducted for R-22, a fixed mass flux of 600 kg/m2s, 5∼30 kW/m2 of wall heat flux, 0.0∼0.9 of local vapor quality. The present experimental data confirmed that the flow boiling heat transfer coefficient in a minichannel varies only by heat flux, independent of mass flux and vapor quality. The effect of tube material was found small for the tubes used in the present work. The present data were well predicted by the correlation proposed by Tran et al. (1996).

An Analytical Model of Flow Boiling Heat Transfer for Slug Flow in a Single Circular Horizontal Micro-Channel

2012 ◽  
Author(s):  
Amen M. Younes ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Slug Flow ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Micro Channel ◽  
Vapor Quality ◽  
Flow Boiling Heat Transfer

Slug flow is one of the most common flow patterns that occur during flow boiling in horizontal micro-channels. In the present work, an analytical model of flow boiling heat transfer is developed for slug flow in a single circular horizontal micro-channel under a uniform heat flux. The heat transfer is affected mainly by the liquid film thickness confined between the vapor slug and the channel wall. For more physical and reliable flow boiling heat transfer model, the liquid film thickness variation and pressure gradient effects on the flow boiling heat transfer coefficient are considered. The influence of vapor quality on heat transfer coefficient, vapor velocity and liquid film velocity is studied. The model is constructed based on the conservation equations of the separated two phase flow. The interphase surface is assumed to be smooth and the flow is a laminar flow. The obtained model applied for flow boiling of R-134a refrigerant in the slug flow at a narrow vapor quality range (0.0 < x < 0.1). The heat transfer coefficient showed a high increase close to the low vapor quality while decreases gradually after the peak. Furthermore, the vapor velocity increases linearly by increasing the vapor quality while, the liquid film velocity decreases.

Experimental Investigation on Flow Boiling in Micro-Channel with R32/R134a

2011 ◽  
Vol 199-200 ◽  
pp. 1574-1578
Author(s):  
Xin Guan ◽  
Hu Gen Ma ◽  
Rong Jian Xie ◽  
Jian Mei Bai ◽  
Hong Liu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Experimental Investigation ◽  
Flow Rate ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Micro Channel ◽  
Refrigerant Mixture ◽  
Flow Boiling Heat Transfer ◽  
The Difference

Mechanism of flow boiling heat transfer in micro-channel and mini-channel with non-azeotropic refrigerant mixture R32/R134a is studied in this paper. Experimental research is carried out at different mass flow rate, heat flux and quality. The difference of heat transfer in two single tubes is analyzed.

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