Investigation of the Effect of Porous Material on the Flow and Temperature Patterns of a Passive Solar Air Heater

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Digpal Kumar ◽  
B. Premachandran
Keyword(s):  
Heat Flux ◽  
Porous Medium ◽  
Porous Material ◽  
Constant Heat Flux ◽  
Surface Radiation ◽  
Electrical Heating ◽  
Solar Air Heater ◽  
Air Heater ◽  
The Difference ◽  
Drying Chamber

Abstract In this work, the effect of flow resistance due to the presence of porous medium representing agricultural products at the exit of free convection-based solar air heater is studied experimentally and numerically. An air heater, along with the drying chamber, is designed as an inclined channel to conduct the experiments. Constant heat flux condition is provided by electrical heating on the top absorber plate of the channel. Experiments are conducted for heat flux ranging from 250 to 750 W/m2 for the channel inclination angle of 30 deg. Porous material bed height is also varied in the drying chamber, while porosity is set at 0.36. The surface-to-surface radiation model is considered for modeling of heat transfer within the flow. For all the heat flux values considered in the experiments, numerical simulations are performed at three different angles of inclinations of 15 deg, 30 deg, and 45 deg. In this analysis, the temperature distribution in the channel wall, the flow pattern, the difference in the mass flowrate, and temperature of the outlet air are investigated with different heights of the porous medium.

scholarly journals Thermohydraulic Performance and Entropy Generation of a Triple-Pass Solar Air Heater with Three Inlets

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6399
Author(s):  
Nguyen Minh Phu ◽  
Ngo Thien Tu ◽  
Nguyen Van Hap
Keyword(s):  
Reynolds Number ◽  
Air Temperature ◽  
Entropy Generation ◽  
Solar Air Heater ◽  
Minimum Entropy ◽  
Air Heater ◽  
The Third ◽  
Thermohydraulic Efficiency ◽  
The Difference ◽  
Minimum Entropy Generation

In this paper, a triple-pass solar air heater with three inlets is analytically investigated. The effects of airflow ratios of the second and third passes (ranging from 0 to 0.4), and the Reynolds number of the third pass (ranging from 8000 to 18,000) on the thermohydraulic efficiency and entropy generation are assessed. An absorber plate equipped with rectangular fins on both sides is used to enhance heat transfer. The air temperature change in the passes is represented by ordinary differential equations and solved by numerical integration. The results demonstrate that the effect of the third pass airflow ratio on the thermohydraulic efficiency and entropy generation is more significant than that of the second pass airflow ratio. The difference in air temperature through the collector shows an insignificant reduction, but the air pressure loss is only 50% compared with that of a traditional triple-pass solar air heater. Increasing the air flow ratios dramatically reduces entropy generation. Multi-objective optimization found a Reynolds number of 11,156 for both the airflow ratio of the second pass of 0.258 and airflow ratio of the third pass of 0.036 to be the an optimal value to achieve maximum thermohydraulic efficiency and minimum entropy generation.

Heat Transfer Characteristics of CuO-Base Oil Nanofluid Laminar Flow Inside Flattened Tubes Under Constant Heat Flux

2010 ◽  
Author(s):  
P. Razi ◽  
M. A. Akhavan-Behabadi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Constant Heat Flux ◽  
Electrical Heating ◽  
Heat Transfer Characteristics ◽  
Constant Heat ◽  
Base Oil ◽  
Transfer Characteristics

An experimental investigation has been carried out to study the heat transfer characteristics of CuO-Base oil nanofluid flow inside horizontal flattened tubes under constant heat flux. The nanofluid flowing inside the tube is heated by an electrical heating coil wrapped around it. The convective heat transfer coefficients of nanofluids are obtained for laminar fully developed flow inside round and flattened tubes. The effect of different parameters such as Reynolds number, flattened tube internal height, nanoparticles concentration and heat flux on heat transfer coefficient is studied. Observations show that the heat transfer performance is improved as the tube profile is flattened. The heat transfer coefficient is increased by using nanofluid instead of base fluid. Also, it can be concluded that decreasing the internal height of the flattened tubes and increasing the concentration of nanoparticles both contribute to the enhancement of heat transfer coefficient.

scholarly journals Chemical Reaction Effects on MHD Free Convective Flow through Porous Medium with Constant Suction and Heat Flux

2016 ◽  
Vol 3 (3) ◽  
Author(s):  
B. Seshaiah ◽  
S.V.K. Varma
Keyword(s):  
Heat Flux ◽  
Porous Medium ◽  
Constant Heat Flux ◽  
Free Convective Flow ◽  
Suction Velocity ◽  
Electrically Conducting ◽  
Electrically Conducting Fluid ◽  
Constant Suction ◽  
Flow Through ◽  
Transfer Flow

<div><p><em>The Objective of the present study is to investigate to free convection and mass transfer flow of a viscous incompressible and electrically conducting fluid through a porous medium bounded by vertical infinite surface with constant suction velocity and constant heat flux under the action of uniform magnetic field applied normal to the direction of flow.</em></p></div>

scholarly journals EFFECT OF CAVITY RATIO ON HEAT TRANSFER BY FREE LOAD FROM HEATED PLATES UPWARD WITH CONSTANT HEAT FLUX

2021 ◽  
Vol 9 (12) ◽  
pp. 686-695
Author(s):  
Waleed Abdulhadiethbayah ◽  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Free Convection ◽  
Electronic Devices ◽  
Experimental Studies ◽  
Constant Heat Flux ◽  
Rate Of Change ◽  
Constant Heat ◽  
The Difference

Many engineering and industrial applications always seek to find ways to dissipate heat from heated surfaces used in these industries. As it is involved in the cooling of electronic parts and electrical transformers, as well as the design of solar collectors, in addition to being a process of heat exchange between hot surfaces and the fluids in contact with them. Since most electronic devices or their parts are cooled by removing the heat generated inside them by using air as a heat transfer medium and in a free convection way, and the fact that heat transfer by free convection occurs in many fields, so there were many studies that dealt with this topic. The free load is generated by the buoyant force (Bouncy force) As a result of the difference in the density of the fluid adjacent to the heated surface due to the difference in temperatures between the fluid and the surface. The laminar flow along surfaces has been extensively studied analytically [1,2,3,4] In the horizontal, inclined and vertical case, whether by constant heat flux or constant surface temperature, there are also many experimental studies of heat transfer by free convection from horizontal, inclined and vertical surfaces with constant heat flux or constant surface temperature [5,6,7,8]. Some experimental studies have also been conducted on heat transfer by convection from heated surfaces in the form of a disk (ring)The outcome of these studies was to extract an exponential mathematical relationship between the average of Nusselt number and the Kirchhoff number or Rayleigh number and the following formula: (Nu=C(Ra) n It is one of the most suitable formulas for heat transfer by free convection from heated surfaces in all its forms and over a wide range of Rayleigh number . It is noted that not all of these studies dealt with the study of the effect of the cavity ratio on heat transfer by free convection from square-shaped surfaces, which is the form that is more applied in electronic devices. Therefore, the current research means studying the rate of change in the average of Nusselt number, which represents a function of the rate of change in the rate of heat transfer by convection, as well as studying the thermal gradient above the surface, and this was done through using three hollow surfaces in proportions (0.25,0.5,0.75) of the total area.

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