scholarly journals Two-dimensional heat transfer coefficients with simultaneous flow visualisations during two-phase flow boiling in a PDMS microchannel

2018 ◽  
Vol 130 ◽  
pp. 624-636 ◽  
Author(s):  
Sofia Korniliou ◽  
Coinneach Mackenzie-Dover ◽  
John R.E. Christy ◽  
Souad Harmand ◽  
Anthony J. Walton ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Phase Flow ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Pdms Microchannel

Review of Correlations of Flow Boiling Heat Transfer Coefficients for Nitrogen

2014 ◽  
Author(s):  
Hao Wang ◽  
Xiande Fang
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Flow Boiling Heat Transfer ◽  
Comparative Review

As an excellent cryogenic cooling medium, Nitrogen (N2) has been used in a variety of engineering fields, where the determination of N2 two-phase flow boiling heat transfer is required. There were some studies evaluating the correlations of flow boiling heat transfer coefficient for N2. However, either the number of correlations covered or the number of data used was limited. This work presents a comparative review of existing correlations of flow boiling heat transfer coefficients for N2 applications. A database of N2 flow boiling heat transfer containing 1043 experimental data points is compiled to evaluate 45 correlations of two-phase flow boiling heat transfer. The experimental parameters cover the ranges of mass flux from 28.0 to 1684.8 kg/m2s, heat flux from 0.2 to 135.6 kW/m2, vapor quality from 0.002 to 0.994, saturation pressure from 0.1 to 3.16 MPa, and channel inner diameter from 0.351 to 14 mm. The results show that the best correlation has a mean absolute deviation of 31.8% against the whole database, suggesting that more efforts should be made to study N2 flow boiling heat transfer to develop a more accurate correlation.

scholarly journals Two-phase flow pattern and heat transfer coefficients of R245fa/R134a under non-uniform heat flux

2019 ◽  
Vol 65 (17) ◽  
pp. 1741-1751
Author(s):  
Yani Lu ◽  
Li Zhao ◽  
Shuai Deng ◽  
Dongpeng Zhao ◽  
Xianhua Nie ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Uniform Heat Flux ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Uniform Heat

scholarly journals Heat Transfer Coefficient Identification in Mini-Channel Flow Boiling with the Hybrid Picard–Trefftz Method

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2057 ◽  
Author(s):  
Mirosław Grabowski ◽  
Sylwia Hożejowska ◽  
Anna Pawińska ◽  
Mieczysław Poniewski ◽  
Jacek Wernik
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Two Phase Flow ◽  
Heat Conduction Problem ◽  
Flow Boiling ◽  
Inverse Heat Conduction Problem ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Trefftz Method

This paper summarizes the results of the flow boiling heat transfer study with ethanol in a 1.8 mm deep and 2.0 mm wide horizontal, asymmetrically heated, rectangular mini-channel. The test section with the mini-channel was the main part of the experimental stand. One side of the mini-channel was closed with a transparent sight window allowing for the observation of two-phase flow structures with the use of a fast film camera. The other side of the channel was the foil insulated heater. The infrared camera recorded the 2D temperature distribution of the foil. The 2D temperature distributions in the elements of the test section with two-phase flow boiling were determined using (1) the Trefftz method and (2) the hybrid Picard–Trefftz method. These methods solved the triple inverse heat conduction problem in three consecutive elements of the test section, each with different physical properties. The values of the local heat transfer coefficients calculated on the basis of the Robin boundary condition were compared with the coefficients determined with the simplified approach, where the arrangement of elements in the test section was treated as a system of planar layers.

Prediction of Two-Phase Heat Transfer Coefficients in a Horizontal Pipe for Different Inclined Positions With Artificial Neural Networks

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Najmeh Sobhanifar ◽  
Ebrahim Ahmadloo ◽  
Sadreddin Azizi
Keyword(s):  
Neural Network ◽  
Heat Transfer ◽  
Experimental Data ◽  
Neural Networks ◽  
Two Phase Flow ◽  
Reynolds Numbers ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients

This paper presents the application of artificial neural network (ANN) in prediction of heat transfer coefficients (HTCs) of two-phase flow of air–water in a pipe in the horizontal and slightly upward inclined (2, 5, and 7 deg) positions. For this purpose, the superficial liquid and gas Reynolds numbers and the inclination of the pipe were used as input parameters, while the HTCs of two-phase flow were used as output parameters in training and testing of the multilayered, feedforward, backpropagation neural networks. In this present study, experimental data were taken from literature and then used for the ANN model. The superficial liquid and gas Reynolds numbers ranged from 740 to 26,100 and 560 to 47,600 for water and air, respectively. The mean deviations against experimental data were determined for the model. Results showed that the network predictions were in very good agreement with the experimental HTC data, whereas the correlation showed more deviations. Finally, results showed that the accuracy between the neural network predictions and experimental data was achieved with mean relative error (MRE) of 2.92% and correlation coefficient (R) that was 0.997 for all datasets, which suggests the reliability of the ANNs as a strong tool for predicting HTCs with two-phase flows.

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