A Model for Predicting Temperature of Electrofusion Joints for Polyethylene Pipes

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Jianfeng Shi ◽  
Jinyang Zheng ◽  
Weican Guo ◽  
Ping Xu ◽  
Yongquan Qin ◽  
...  
Keyword(s):  
Thermal Contact ◽  
Power Input ◽  
Ultrasonic Test ◽  
Thermal Contact Conductance ◽  
Transfer Model ◽  
Contact Conductance ◽  
One Dimensional ◽  
Polyethylene Pipes ◽  
Heating Wire ◽  
Good Agreement

With the increasing application of electrofusion (EF) welding in connecting polyethylene (PE) pipes for gas distribution, more effort has been invested to ensure the safety of the pipeline systems. The objective of this paper is to investigate and understand the temperature distribution during EF welding. A one-dimensional transient heat-transfer model was proposed, taking the variation in the rate of power input, the phase transition of PE, and the thermal contact conductance between heating wire and PE into consideration. Then, experiments were designed to verify the power input and the temperature. The measured values of the power input were shown to be in good agreement with the analytical results. Based on ultrasonic test (UT), a new “Eigen-line” method was presented, which overcomes the difficulties found in the thermocouples’ temperature measurements. The results demonstrate good agreements between prediction and experiment. Finally, based on the presented model, a detailed parametric study was carried out to investigate the influences of the variation in the power input, the physical properties of PE, and the thermal contact conductance between heating wire and surrounding PE.

A Model for Predicting Temperature of Electrofusion Joints for Polyethylene Pipes

2008 ◽  
Author(s):  
Jianfeng Shi ◽  
Jinyang Zheng ◽  
Weican Guo
Keyword(s):  
Thermal Contact ◽  
Average Power ◽  
Welding Process ◽  
Input Voltage ◽  
Power Input ◽  
Temperature Fields ◽  
Thermal Contact Conductance ◽  
Measured Temperature ◽  
Contact Conductance ◽  
Heating Wire

Polyethylene (PE) pipe with electrofusion (EF) joints is widely used in the areas of gas distribution. Understanding and predicting the temperature during welding is crucial for ensuring the joint quality. The EF joining is generally conducted by applying a constant voltage to the heating wire. As the welding process develops, both the temperature and the resistance of the heating wire increase, which leads to a decrease in the rate of power input with increasing fusion time. However, the existing models for temperature prediction have not taken the change in the rate of power input into account. By comprehensively considering the variation in the rate of power input, the phase transition of PE and the thermal contact conductance between the heating wire and PE, the authors established an analytical model for predicting the temperature. Experiments are designed and the power inputs measured are shown to be in good agreement with the analytical results, in contrast to the interrogative measured temperature. In order to verify the temperature fields, the authors employ a new “Eigen-line” method based on ultrasonic tests which overcomes the difficulties found in the measuring methods by thermocouples. The experimental results also show good agreements. The developed model is then used to investigate the influence of the decline in the power input, physical properties of PE and the thermal contact conductance between heating wire and surrounding PE. It is found that the average power input is in proportion to the input voltage, and the temperature profile is greatly affected by the power decline and specific heat capacity. The proposed model can be used to optimize the welding specification.

A New Method for Measuring Thermal Contact Conductance: Experimental Technique and Results

2008 ◽  
Author(s):  
Simon Woodland ◽  
Andrew D. Crocombe ◽  
John W. Chew ◽  
Stephen J. Mills
Keyword(s):  
Thermal Contact ◽  
New Method ◽  
Thermal Contact Conductance ◽  
Metal Working ◽  
Loading History ◽  
Test Rig ◽  
Contact Conductance ◽  
Pressure Surface ◽  
Surface Flatness ◽  
Good Agreement

Thermal contact conductance (TCC) is used to characterise heat transfer across interfaces in contact. It is important in thermal modelling of turbomachinery components and finds many other applications in the aerospace, microelectronic, automotive and metal working industries. A new method for measuring TCC is described and demonstrated. A test rig is formed from an instrumented split tube with washers in-between and loading applied in controlled conditions. The experimental method and data analysis is described, and the effect on thermal contact conductance of parameters such as contact pressure, surface roughness, surface flatness and loading history is investigated. The results of these tests are compared to those in the available literature and good agreement of trends is found. However, the tests conducted to measure the effect of load cycling on TCC have found that the TCC continues to increase beyond 20 or so load cycles, contrary to some results in the literature.

Fractal Model for Thermal Contact Conductance

2008 ◽  
Vol 130 (10) ◽  
Author(s):  
Mingqing Zou ◽  
Boming Yu ◽  
Jianchao Cai ◽  
Peng Xu
Keyword(s):  
Random Number ◽  
Rough Surfaces ◽  
Thermal Contact ◽  
Fractal Model ◽  
Thermal Contact Conductance ◽  
Bulk Resistance ◽  
Contact Conductance ◽  
Proposed Model ◽  
Fractal Parameters ◽  
Good Agreement

A random number model based on fractal geometry theory is developed to calculate the thermal contact conductance (TCC) of two rough surfaces in contact. This study is carried out by geometrical and mechanical investigations. The present study reveals that the fractal parameters D and G have important effects on TCC. The predictions by the proposed model are compared with existing experimental data, and good agreement is observed by fitting parameters D and G. The results show that the effect of the bulk resistance on TCC, which is often neglected in existing models, should not be neglected for the relatively larger G and D. The main advantage of this model is the randomization of roughness distributions on rough surfaces. The present results also show a better agreement with the practical situation than the results of other models. The proposed technique may have the potential in prediction of other phenomena such as friction, radiation, wear and lubrication on rough surfaces.

Thermal Contact Conductance Across Gold-Coated OFHC Copper Contacts in Different Media

2005 ◽  
Vol 127 (6) ◽  
pp. 657-659 ◽  
Author(s):  
Bapurao Kshirsagar, ◽  
Prashant Misra, ◽  
Nagaraju Jampana, and ◽  
M. V. Krishna Murthy
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Contact Pressure ◽  
Thermal Contact ◽  
High Conductivity ◽  
Thermal Contact Conductance ◽  
Ofhc Copper ◽  
Contact Conductance ◽  
Contact Pressures ◽  
Good Agreement

The thermal contact conductance studies across gold-coated oxygen-free high-conductivity copper contacts have been conducted at different contact pressures in vacuum, nitrogen, and helium environments. It is observed that the thermal contact conductance increases not only with the increase in contact pressure but also with the increase in thermal conductivity of interstitial medium. The experimental data are found to be in good agreement with the literature.

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