Turbulent mixed convection of air in a cavity with a heat-conducting inner solid: Effect of surface radiation and thermal diffusivity on heat transfer and exergy destruction

2021 ◽  
pp. 107035
Author(s):  
Diego R. Rivera ◽  
Nelson O. Moraga
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Mixed Convection ◽  
Surface Radiation ◽  
Heat Conducting ◽  
Exergy Destruction ◽  
Solid Effect ◽  
Effect Of Surface

Optimal Distribution of Discrete Heat Sources Under Mixed Convection—A Heuristic Approach

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Tapano Kumar Hotta ◽  
C. Balaji ◽  
S. P. Venkateshan
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Optimal Configuration ◽  
Surface Radiation ◽  
Horizontal Wind ◽  
Maximum Temperature ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Temperature Excess ◽  
Effect Of Surface

Steady state experiments are conducted in a low speed horizontal wind tunnel under mixed convection for five discrete heat sources (aluminum) of nonidentical sizes arranged at different positions on a substrate board (bakelite) to determine the optimal configuration. The optimal configuration is one for which the maximum temperature excess (difference between the maximum temperature among the heat sources of that configuration, and the ambient temperature) is the lowest among all the other possible configurations and is determined by a heuristic nondimensional geometric parameter λ. The maximum temperature excess is found to decrease with λ, signifying an increase in heat transfer coefficient. In view of this, the configuration with highest λ is deemed to be the optimal one. The effect of surface radiation on the heat transfer characteristic of heat sources is also studied by painting their surface with black, which reduces their temperature by as much as 12%. An empirical correlation is developed for the nondimensional maximum temperature excess (θ) in terms of λ, by taking into account the effect of surface radiation. The correlation when applied for highest λ of the configuration returns the minimum value of θ at the optimal condition, which is a key engineering quantity that is sought in problems of this class.

Effect of Surface Emissivity on Conjugate Turbulent Natural Convection in an Air-Filled Cavity with a Heat Source

2016 ◽  
Vol 685 ◽  
pp. 315-319 ◽  
Author(s):  
Igor V. Miroshnichenko ◽  
Mikhail A. Sheremet
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Surface Radiation ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Heat Conducting ◽  
Surface Emissivity ◽  
Turbulent Natural Convection ◽  
Effect Of Surface

The interaction of conjugate turbulent natural convection and surface thermal radiation in an air-filled square enclosure having heat-conducting solid walls of finite thickness and a heat source has been numerically studied. The primary focus was on the influence of surface emissivity on complex heat transfer. The mathematical model has been formulated in dimensionless variables such as stream function, vorticity and temperature using k-ε turbulent model. The effect of surface emissivity on the average total Nusselt number has been defined. The distributions of streamlines and temperature fields, describing characteristics of the analyzed fluid flow and heat transfer have been obtained. The results clearly show an essential effect of surface radiation on unsteady turbulent heat transfer.

Optimal Distribution of Discrete Heat Sources Under Mixed Convection: A Heuristic Approach

2013 ◽  
Author(s):  
Tapano Kumar Hotta ◽  
C. Balaji ◽  
S. P. Venkateshan
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Optimal Configuration ◽  
Surface Radiation ◽  
Horizontal Wind ◽  
Maximum Temperature ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Temperature Excess ◽  
Effect Of Surface

Steady state experiments are conducted in a low speed horizontal wind tunnel under mixed convection regime, for five discrete heat sources (Aluminum) of different sizes arranged at different positions on a substrate board (Bakelite), to determine the optimal configuration. The characteristic length of heat sources varies from 0.005 to 0.011 m. The optimal configuration is one whose maximum temperature excess (temperature difference between the heat source and ambient) is minimum among all the possible configuration of heat sources mounted on the substrate board, and is determined by a heuristic non-dimensional geometric parameter λ. The maximum temperature excess is found to decrease with λ, signifying an increase of heat transfer coefficient. In view of this, configuration with the highest λ value is the optimal one. The effect of surface radiation on the heat transfer characteristic has also been studied by painting the surface of heat sources with black paint, which reduces their temperature by as much as 12%. An empirical correlation is developed for the non-dimensional temperature excess (θ) by taking into account the effect of surface radiation. The correlation when applied for the highest λ to the configuration, returns the maximum value of θ at the optimal value, which is a key engineering quality that is sought in problems of this class.

Experimental Study on Mixed Convection Heat Transfer for Thermally Developing Flow in Horizontal Ducts With Radiation Effects

2011 ◽  
Author(s):  
Rajamohan Ganesan ◽  
Ramesh Narayanaswamy ◽  
Alexander Gorin ◽  
Kumar Perumal
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Cross Section ◽  
Convection Heat Transfer ◽  
Total Heat ◽  
Surface Radiation ◽  
Convection Heat ◽  
Total Heat Transfer ◽  
Aspect Ratios ◽  
Mixed Convection Heat Transfer

This research focuses on the interaction of surface radiation with laminar mixed convection heat transfer for thermally developing airflow in horizontal ducts. The duct cross section is made of two differentially heated isothermal vertical walls and two adiabatic horizontal walls. In a series of experiments, the Reynolds number is varied from about Re = 800 to Re = 1200, for two aspect ratios of the duct cross section. The hot wall temperature ranges from 27°C to 100 °C, and the emissivity of internal walls are 0.05 and 0.85. The total heat transfer from the hot wall to the cold wall of the duct depends on the mixed convection and also on the surface radiation heat transfer that takes place within the duct. Therefore, it is important that the effects of surface radiation must be properly understood, and accounted for, in the design and analysis of flow and heat transfer through ducts. The results presented here show the effect of surface radiation and mixed convection on the total heat transfer rate within the duct. The flow field within the duct is also made visible by a suitable smoke flow visualization method.

Effect of Surface Radiation on Conjugate Natural Convection in a Square Enclosure with a Tube at Different Locations

2013 ◽  
Vol 281 ◽  
pp. 190-196 ◽  
Author(s):  
Jian Sheng Wang ◽  
Yong Xu
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Surface Radiation ◽  
Square Enclosure ◽  
Conjugate Natural Convection ◽  
Different Temperatures ◽  
Vertical Walls ◽  
Effect Of Surface

The conjugate natural convection heat transfer with and without the interaction of the surface radiation in a square enclosure was carried out by numerical simulation. The vertical walls of the square enclosure were heated with different temperatures, and the others were adiabatic. A circular tube was inserted into the square enclosure. It was observed that varied location of the tube center can lead to different motion and heat transfer intensities. In addition, surface radiation reduces the convective heat transfer in the square enclosure compared to the pure natural convection case and enhances the overall heat transfer performance.

scholarly journals Finite Element Analysis of Mixed Convection in a Rectangular Cavity with a Heat-Conducting Horizontal Circular Cylinder

2009 ◽  
Vol 14 (2) ◽  
pp. 217-247 ◽  
Author(s):  
Md. M. Rahman ◽  
M. A. Alim ◽  
M. A. H. Mamun
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Heat Source ◽  
Mixed Convection ◽  
Rectangular Cavity ◽  
Heated Wall ◽  
Physical Parameters ◽  
Element Formulation ◽  
Heat Conducting ◽  
Coupled Equations

. Combined free and forced convection in a two dimensional rectangular cavity with a uniform heat source applied on the right vertical wall is studied numerically. A circular heat conducting horizontal cylinder is placed somewhere within the cavity. The present study simulates a practical system, such as a conductive material in an inert atmosphere inside a furnace with a constant flow of gas from outside. Importance is placed on the influences of the configurations and physical properties of the cavity. The development mathematical model is governed by the coupled equations of continuity, momentum and energy and is solved by employing Galerkin weighted residual finite element method. In this paper, a finite element formulation for steadystate incompressible conjugate mixed convection and conduction flow is developed. The computations are carried out for wide ranges of the governing parameters, Reynolds number (Re), Richardson number (Ri), Prandtl number (Pr) and some physical parameters. The results indicate that both the heat transfer rate from the heated wall and the dimensionless temperature in the cavity strongly depend on the governing parameters and configurations of the system studied, such as size, location, thermal conductivity of the cylinder and the location of the inflow and outflow opening. Detailed results of the interaction between forced airstreams and the buoyancy-driven flow by the heat source are demonstrated by the distributions of streamlines, isotherms and heat transfer coefficient.

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