Numerical Analysis of Convection Heat Transfer From an Array of Circular Perforated Fins due to Variable Perforation Size

2012 ◽  
Author(s):  
A. H. Dastbelaraki ◽  
M. Yaghoubi
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Stokes Equations ◽  
Experimental Studies ◽  
Convection Heat Transfer ◽  
Heat Removal ◽  
Industrial Applications ◽  
Working Fluid ◽  
Manufacturing Cost ◽  
Convection Heat

Among rapid advances of electrical systems electronic circuit boards have become more compact and heat production rate from their components increased considerably. Such developments raised more attention and tendency in tackling their cooling problems. A wide variety of cooling systems are developed such as various fins for decreasing the circuit board temperature. Extended surfaces or fins are good heat transfer equipments that are used for various industrial applications. The wide industrial applications of fins to enhance heat transfer rate highlighted the need for further research of optimization of fins to increase their thermal performances. Among various fin types, rectangular fins are commonly used due to their simplicity of manufacturing. Fin configurations affect the cooling rate significantly, hence a comprehensive parametric study on the fin geometries may be improve their performance. Rectangular fins show a good performance of increasing heat removal rate, while reducing the manufacturing cost. Moreover the inspiration of putting holes along the flow through the fins may be very helpful in increasing the heat removal and reduction of the needed material. The present study investigates a numerical analysis of three dimensional, turbulent convection heat transfer from an array of rectangular perforated fins with increasing the perforation size from bottom to top. The perforations considered are like circular channels along the length of fins and the number of perforations is 3. For investigation, incompressible air as working fluid is modeled using Navier–Stokes equations. RNG based k-ε turbulent model is used to predict turbulent flow parameters. Temperature field inside the fins is obtained by solving Fourier’s conduction equation. The conjugate differential equations for both solid and gas phase are solved simultaneously by finite volume procedure using SIMPLE algorithm. Flow and heat transfer characteristics are presented for Reynolds numbers from 2 × 104 to 4 × 104 based on the fin length and Prandtl number of Pr = 0.71. Numerical model is first validated with previous experimental studies and good agreements were observed. Based on the valid simulation model, numerical solution is made to find flow field and temperature distribution for various perforation size. Results show that for a specific type of perforated fins the fin effectiveness is higher than other types and drag coefficient decreases with increasing the perforation size.

Influence of Flow Acceleration on Convection Heat Transfer of CO2 at Supercritical Pressures and Air in a Vertical Micro Tube

2010 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Rui-Na Xu ◽  
Zhi-Hui Li ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Convection Heat ◽  
Downward Flow ◽  
Flow Acceleration ◽  
Flow And Heat Transfer

The convection heat transfer of CO2 at supercritical pressures in a 0.0992 mm diameter vertical tube at relatively high Reynolds numbers (Rein = 6500), various heat fluxes and flow directions are investigated experimentally and numerically. The effects of buoyancy and flow acceleration resulting from the dramatic property variations are studied. The Results show that the local wall temperature varied non-linearly for both upward and downward flow when the heat flux was high. The difference in the local wall temperature between upward and downward flow is very small when the other test conditions are held the same, which indicates that for supercritical CO2 flowing in a micro tube as employed in this study, the buoyancy effect on the convection heat transfer is insignificant and the flow acceleration induced by the axial density variation with temperature is the main factor leading to the abnormal local wall temperature distribution at high heat fluxes. The predicted temperatures using the LB low Reynolds number turbulence model correspond well with the measured data. To further study the influence of flow acceleration on the convection heat transfer, air is also used as the working fluid to numerically investigate the fluid flow and heat transfer in the vertical micro tube. The results show that the effect of compressibility on the fluid flow and heat transfer of air in the vertical micro tube is significant but that the influence of thermal flow acceleration on convection heat transfer of air in a vertical micro tube is insignificant.

Experimental Study on Natural Convection Heat Transfer Outside Tube Bundle in Space Under Low Temperature Difference

2020 ◽  
Author(s):  
Junxiu Xu ◽  
Ming Ding ◽  
Changqi Yan ◽  
Guangming Fan
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Low Temperature ◽  
Tube Bundle ◽  
Convection Heat Transfer ◽  
Heat Removal ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Reactor Pool ◽  
Residual Heat

Abstract The Passive Residual Heat Removal System (PRHRS) is very important for the safety of the heating reactor after shutdown. PRHRS is a natural circulation system driven by density difference, therefore, the heat transfer performance of the Passive Residual Heat Removal Heat Exchanger (PRHR HX) has a great impact to the heat transfer efficiency of PRHRS. However, the most research object of PRHR HX is the C-shape heat exchanger at present, which located in In-containment Refueling Water Storage Tank (IRWST). This heat exchanger is mainly used for the PRHRS of nuclear power plants. In the swimming pool-type low-temperature heating reactor (SPLTHR), the PRHR HX is placed in the reactor pool, which the pressure and temperature of the reactor pool are relatively low, and the outside heat transfer mode of tube bundle is mainly natural convection heat transfer. In this study, a miniaturized single-phase pool water cooling system was built to investigate the natural convective heat transfer coefficient of the heat exchanger under the large space and low temperature conditions. The experimental data had been compared with several correlations. The results show that the predicted value of Yang correlation is the closest to the experimental data, which the maximum deviation is about 11%.

A Numerical Study of Eccentricity Effect to Heat Transfer Under Single Phase Force Convection Inside a Vertical Annulus

2013 ◽  
Author(s):  
Yang Liu ◽  
Qianqian Jia ◽  
Haijun Jia
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Stokes Equations ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Force Convection ◽  
Convection Heat ◽  
Eccentric Annulus ◽  
Eccentricity Effect ◽  
Vertical Annulus

Because annulus channel can be used to develop high efficiency compact heat exchangers, the heat transfer in annulus channel has become great interest to researchers in recent years. Most of the studies focus on the vertical concentric and horizontal eccentric annulus. The investigations about single phase force convection heat transfer inside a vertical eccentric annulus are not enough. In this work, force convection heat transfer is numerically studied to determine the eccentricity effect inside a vertical annulus. For this purpose, full Reynolds-averaged Navier-Stokes equations along with energy equations are solved in a 3-D grid. The discrete method of the equations is based on finite-volume method and the turbulence model is RNG k-ε model. The radius ratio of the annulus is 0.8 in this work. Heat flux of one wall is constant while the other is insulated. Firstly, the feasibility and exactness of the numerical method is proved by comparing the Nusselt number with experiment in concentric annulus. Then the effect of eccentricity is studied in detail.

Identification of the Coherent Structures in Multiple Impinging Jets

2011 ◽  
Author(s):  
Martin Draksler ◽  
Bosˇtjan Koncˇar
Keyword(s):  
Heat Transfer ◽  
Coherent Structures ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Heat Removal ◽  
Local Heat ◽  
Impinging Jets ◽  
Industrial Applications ◽  
Interaction Region ◽  
Flow Structures

An array of impinging jets is characterized by high heat removal capability. As such it is used as a cooling technique in various industrial applications, i.e. paper drying, turbine blades cooling etc. The objective of the current study is to analyze the coherent structures in the interaction region of impinging jets and relate them to the local heat transfer. Since they play the major role in the local heat enhancement, their proper identification is crucial for the understanding of the heat transfer mechanisms. Three different methods for identification of flow structures in the jet interaction region are discussed in the paper. Heat transfer capability of different jet arrangements (in-line and hexagonal) are compared and analyzed in the context of flow structures comparison. The numerical simulations were performed with the CFD code ANSYS-CFX, solving Reynolds Averaged Navier-Stokes Equations (RANS approach). For the turbulence modeling Shear Stress Transport (SST) turbulence model was used.

Sign in / Sign up

Export Citation Format

Share Document