scholarly journals Effect of Compression on Contact Heat Transfer in Thermal Protective Clothing Under Different Moisture Contents

2019 ◽  
Vol 38 (1) ◽  
pp. 19-31 ◽  
Author(s):  
Yun Su ◽  
Rui Li ◽  
Jie Yang ◽  
Guowen Song ◽  
Jun Li
Keyword(s):  
Heat Transfer ◽  
Moisture Content ◽  
Protective Clothing ◽  
Transfer Efficiency ◽  
Protective Level ◽  
Contact Heat ◽  
Contact Heat Transfer ◽  
Heat Transfer Efficiency ◽  
Skin Contact ◽  
Thermal Protective Clothing

Contact burns pose a serious threat on firefighters’ health, safety, and job performance. The objective of the study was to analyze the effects of compression and moisture content on thermal protective performance of clothing. Skin-simulant sensor and Pennes bio-heat transfer model were used to predict time to cause skin contact burn. A new index (heat transfer efficiency) was proposed to examine the effects of applied pressure and moisture level on the contact heat transfer in the thermal protective clothing. It was demonstrated that the addition of moisture nonlinearly decreased the thermal protective level of clothing. The fabric thickness was greatly decreased by the compression, but the thermal protective level presented no significant difference between two kinds of pressures. The heat transfer efficiency was an effective index for evaluating the contact heat transfer, which was determined by the basic properties of fabric, the moisture content, and the pressure level. The conclusions from this study could contribute to understanding the effects of compression and moisture on the contact heat transfer, thus providing the principle of thermal protection against skin contact burns.

Hydrodynamic Features of Contact Heat-Transfer Packing Devices

1997 ◽  
Vol 28 (4-6) ◽  
pp. 393-397
Author(s):  
N. Yu. Koloskova ◽  
V. V. Dubrovskaya ◽  
V. V. Orlyanskii
Keyword(s):  
Heat Transfer ◽  
Contact Heat ◽  
Contact Heat Transfer

CFD-based structure optimization of plate bundle in plate-fin heat exchanger considering flow and heat transfer performance

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yao Li ◽  
Haiqing Si ◽  
Jingxuan Qiu ◽  
Yingying Shen ◽  
Peihong Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Field Performance ◽  
High Specific Surface Area ◽  
Calculation Model ◽  
Air Separation ◽  
Transfer Efficiency ◽  
Heat Transfer Efficiency

Abstract The plate-fin heat exchanger has been widely applied in the field of air separation and aerospace due to its high specific surface area of heat transfer. However, the low heat transfer efficiency of its plate bundles has also attracted more attention. It is of great significance to optimize the structure of plate-fin heat exchanger to improve its heat transfer efficiency. The plate bundle was studied by combining numerical simulation with experiment. Firstly, according to the heat and mass transfer theory, the plate bundle calculation model of plate-fin heat exchanger was established, and the accuracy of the UDF (User-Defined Functions) for describing the mass and heat transfer was verified. Then, the influences of fin structure parameters on the heat and mass transfer characteristics of channel were discussed, including the height, spacing, thickness and length of fins. Finally the influence of various factors on the flow field performance under different flow states was integrated to complete the optimal design of the plate bundle.

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

Development of Heat Exchanger Fouling Model and Preventive Maintenance Diagnostic Tool

2007 ◽  
Vol 2 (2) ◽  
Author(s):  
H. Zabiri ◽  
V. R. Radhakrishnan ◽  
M. Ramasamy ◽  
N. M. Ramli ◽  
V. Do Thanh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Predictive Model ◽  
Diagnostic Tool ◽  
Preventive Maintenance ◽  
Heat Exchangers ◽  
Waste Heat ◽  
A Priori ◽  
Transfer Efficiency ◽  
Heat Transfer Efficiency

The Crude Preheat Train (CPT) is a set of large heat exchangers which recover the waste heat from product streams back to preheat the crude oil. The overall heat transfer coefficient in these heat exchangers may be significantly reduced due to fouling. One of the major impacts of fouling in CPT operation is the reduced heat transfer efficiency. The objective of this paper is to develop a predictive model using statistical methods which can a priori predict the rate of the fouling and the decrease in heat transfer efficiency in a heat exchanger in a crude preheat train. This predictive model will then be integrated into a preventive maintenance diagnostic tool to plan the cleaning of the heat exchanger to remove the fouling and bring back the heat exchanger efficiency to their peak values. The fouling model was developed using historical plant operating data and is based on Neural Network. Results show that the predictive model is able to predict the shell and tube outlet temperatures with excellent accuracy, where the Root Mean Square Error (RMSE) obtained is less than 1%, correlation coefficient R2 of approximately 0.98 and Correct Directional Change (CDC) values of more than 90%. A preliminary case study shows promising indication that the predictive model may be integrated into a preventive maintenance scheduling for the heat exchanger cleaning.

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