Ray-Thermal Sequential Coupled Heat Transfer ANALYSIS of Porous Media Receiver for Solar Dish Collector

2013 ◽  
Vol 442 ◽  
pp. 169-175 ◽  
Author(s):  
Fu Qiang Wang
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Porous Media ◽  
Flux Distribution ◽  
Heat Transfer Analysis ◽  
Uniform Heat Flux ◽  
Heat Flux Distribution ◽  
Uniform Heat ◽  
Distribution Boundary

For the sake of reflecting the concentrated heat flux distribution boundary condition as genuine as possible during simulation, the sequential coupled optical-thermal heat transfer analysis is introduced for porous media receiver. During the sequential coupled numerical analysis, the non-uniform heat flux distribution on the fluid entrance surface of porous media receiver is obtained by Monte-Carlo ray tracing method. Finite element method (FEM) is adopted to solve energy equation using the calculated heat flux distribution as the third boundary condition. The dimensionless temperature distribution comparisons between uniform and non-uniform heat flux distribution boundary conditions, various porosities, and different solar dish concentrator tracking errors are investigated in this research.

Co-Axial Laminar Multiphase Jet: A Novel Methodology for the Attainment Enhancement in Transition Boiling Regime

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Kashinath Barik ◽  
B. Swain ◽  
A.R. Pati ◽  
Susmit Chitransh ◽  
S.S. Mohapatra
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Distribution ◽  
Flow Behavior ◽  
Heat Transfer Analysis ◽  
Heat Flux Distribution ◽  
Low Mass ◽  
Multiphase Fluid ◽  
Thermal Diffusivities ◽  
The Comparative Study

Abstract In the current investigation, by using a very low mass flux co-axial laminar multiphase fluid jet, enhancement in heat transfer rate, uniformity in heat flux distribution, and reduction in coolant consumption rate characteristics are simultaneously tried to achieve in case of cooling from a very high initial temperature (900 °C). The information on quenching technology depicting all the above-mentioned advantages has not been reported in the literature. In the present work, kerosene–water, nanofluid (Al2O3 = 0.15%)–kerosene, and nanofluid (Al2O3 = 0.15%)–polyethylene glycol combinations were used for co-axial cooling experimentation. From the heat transfer analysis, it is observed that nanofluid (Al2O3 = 0.15%) and kerosene combination produces maximum critical heat flux due to the alteration of thermophysical and interfacial properties, which enhance the driving force and flow behavior defining momentum and thermal diffusivities in the favorable direction of heat transfer, respectively. In addition to the above, the comparative study ensures a significant reduction in coolant consumption and augmentation in uniformity in heat flux distribution.

Critical Heat Flux in Tubes With Cosine Axial Heat Flux

2005 ◽  
Author(s):  
W. Jaewoo Shim ◽  
Joo-Yong Park ◽  
Ji-Su Lee ◽  
Dong Kook Kim
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Flux Distribution ◽  
Average Error ◽  
Uniform Heat Flux ◽  
Heat Flux Distribution ◽  
Uniform Heat ◽  
System Pressure ◽  
Data Points

In this study a method to predict CHF (Critical Heat Flux) in vertical round tubes with cosine heat flux distribution was examined. For this purpose a uniform correlation, based on local condition hypothesis, was developed from 9,366 CHF data points of uniform heat flux heaters. The CHF data points used were collected from 13 different sources had the following parameter ranges: 1.01 ≤ P (pressure) ≤ 206.79 bar, 9.92 ≤ G (mass flux) ≤ 18,619.39 kg/m2s, 0.00102 ≤ D (diameter) ≤ 0.04468 m, 0.0254 ≤ L (length) ≤ 4.966 m, 0.11 ≤ qc (CHF) ≤ 21.42 MW/m2, and −0.87 ≤ X (exit qualities) ≤ 1.58. The result of this work showed that the uniform CHF correlation could be used to predict CHF accurately in a non-uniform heat flux heater for wide flow conditions. Furthermore, the location, where CHF occurs in non-uniform heat flux distribution, can also be determined accurately with the local variables: the system pressure (P), tube diameter (D), mass flux of water (G), and true mass flux of vapor (GXt). The new correlation predicted CHF with cosine heat flux, 297 data points from 5 different published sources, within the root mean square error of 12.42% and average error of 1.06% using the heat balance method.

scholarly journals A novel method to realize a non-uniform heat flux distribution through the variable-speed scanning of an electron beam

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chuanmao Zheng ◽  
Hongxin Yao ◽  
Xiyao Wang ◽  
Hong Ye
Keyword(s):  
Heat Flux ◽  
Electron Beam ◽  
Flux Distribution ◽  
Uniform Heat Flux ◽  
Variable Speed ◽  
Heat Flux Distribution ◽  
Uniform Heat ◽  
Hypersonic Wind Tunnel ◽  
Flux Boundary Conditions ◽  
Novel Method

AbstractQuartz lamp heaters and hypersonic wind tunnel are currently applied in thermal assessment of heat resistant materials and surface of aircraft. However, it is difficult to achieve precise heat flux distribution by quartz lamp heaters, while enormous energy is required by a large scale hypersonic wind tunnel. Electron beam can be focused into a beam spot of millimeter scale by an electromagnetic lens and electron-magnetically deflected to achieve a rapid scanning over a workpiece. Moreover, it is of high energy utilization efficiency when applying an electron beam to heat a metal workpiece. Therefore, we propose to apply an electron beam with a variable speed to establish a novel method to realize various non-uniform heat flux boundary conditions. Besides, an electron beam thermal assessment equipment is devised. To analyze the feasibility of this method, an approach to calculate the heat flux distribution formed by an electron beam with variable-speed scanning is constructed with beam power, diameter of the beam spot and dwell duration of the electron beam at various locations as the key parameters. To realize a desired non-uniform heat flux distribution of the maximum gradient of 1.1 MW/m3, a variable-speed scanning strategy is constructed on basis of the conservation of energy. Compared with the desired heat flux, the maximum deviation of the scanned heat flux is 4.5% and the deviation in the main thermal assessment area is less than 3%. To verify the method, taking the time-average scanned heat flux as the boundary condition, a heat transfer model is constructed and temperature results are calculated. The experiment of variable-speed scanning of an electron beam according to the scanning strategy has been carried out. The measured temperatures are in good agreement with the predicted results at various locations. Temperature fluctuation during the scanning process is analyzed, and it is found to be proportional to the scanned heat flux divided by volumetric heat capacity, which is applicable for different materials up to 3.35 MW/m2. This study provides a novel and effective method for precise realization of various non-uniform heat flux boundary conditions.

Three Dimensional Numerical Simulation of Gas Heat Transfer in Rectangular Microchannels

2010 ◽  
Author(s):  
Xiaohong Yan ◽  
Qiuwang Wang
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Wall Temperature ◽  
Three Dimensional ◽  
Uniform Heat Flux ◽  
Flux Boundary Condition ◽  
Uniform Heat ◽  
Heat Flux Boundary Condition

Rectangular microchannel is the typical component of the micro heat exchangers and micro heat sinks. Three-dimensional compressible Navier-Stokes equations are solved for gas flow and heat transfer in microchannels under uniform heat flux boundary condition. The numerical methodology is based on the control volume SIMPLE scheme. It is found that the heat removal characteristic for compressible flow is better than the incompressible flow and it is not suitable to use conventionally defined Nu to measure the heat transfer characteristic for compressible heat transfer. The effect of the aspect ratio (width to height) on the cross-sectional averaged wall temperature and the Nu is negligible under the uniform heat flux boundary condition. However, the local uniformity of the wall temperature is significantly influenced by the aspect ratio. The square cross-section exhibits the best local uniformity of the wall temperature.

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