scholarly journals Natural Convection Cooling of a Heat Source Placed at the Bottom of a Square Cavity. Effect of Source Length, Position, Thermal Condition and Prandtl Number

2020 ◽  
Vol 38 (3) ◽  
pp. 722-737
Author(s):  
Abderrahmane Horimek ◽  
El-Amria Nekag
Keyword(s):  
Exchange Rate ◽  
Natural Convection ◽  
Heat Exchange ◽  
Heat Source ◽  
Prandtl Number ◽  
Thermal Conditions ◽  
Effect Analysis ◽  
Bottom Side ◽  
D Values ◽  
Good Heat

Cooling process of a heat source placed at the bottom side of a cold-walled cavity (TC) by means of natural convection has been studied numerically in this work. Two thermal conditions have been assumed at the source (q-imposed or T-imposed). The effects of Rayleigh number (Ra=10+3→10+6), source length (SL=0.1→1.0), source position (D) compared to left side, in addition to the effect of the number of Prandtl (Pr=0.71→10+2) were analyzed with ample details. For a source at the center of the bottom side, results showed an increase of flow and temperature disturbance with increasing Ra and/or SL, with an enhancement of both local and mean Nusselt numbers. Particular exceptions were noticed for high Ra values for the second heating type. For all considerations, the case of SL=0.1 makes an exception where a very good heat exchange rate is recorded. When the source is no longer centered, Clearer difference between this case and the previous one was recorded, especially for small D values. Very good heat exchange rate is recorded for D=0.0 for all considerations, with remarkable amount of difference compared the closest one to it, followed by a progressive decrease until the case of source at the center. Finally, Prandtl number (Pr) effect analysis showed an increase of the heat transfer rate with a clear amount from Pr=0.71 until Pr=5.0, followed by a slight increase for higher Pr values until stabilization for Pr>50.0. The good exploitation of the intervening parameters’ parameters, allows ensuring the best cooling of the source.

Numerical Survey of the Melting Driven Natural Convection Using Generation Heat Source: Application to the Passive Cooling of Electronics Using Nano-Enhanced Phase Change Material

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Hamza Faraji ◽  
Mustapha Faraji ◽  
Mustapha El Alami
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Phase Change ◽  
Phase Change Material ◽  
Metallic Nanoparticles ◽  
Simple Algorithm ◽  
Bottom Side ◽  
Volume Method ◽  
Change Material

Abstract The present paper reports numerical results of the melting driven natural convection in an inclined rectangular enclosure filled with nano-enhanced phase change material (NePCM). The enclosure is heated from the bottom side by a flush-mounted heat source (microprocessor) that generates heat at a constant and uniform volumetric rate and mounted on a substrate (motherboard). All the walls are considered adiabatic. The purpose of the investigation is analyzing the effect of nanoparticles insertion by quantifying their contribution to the overall heat transfer. Combined effects of the PCM type, the inclination angle and the nanoparticles fraction on the structure of the fluid flow and heat transfer are investigated. A 2D mathematical model based on the conservation equations of mass, momentum, and energy was developed. The governing equations were integrated and discretized using the finite volume method. The SIMPLE algorithm was adopted for velocity–pressure coupling. The obtained results show that the nanoparticles insertion has an important quantitative effect on the overall heat transfer. The insertion of metallic nanoparticles with different concentrations affects the thermal behavior of the heat sink. They contribute to an efficient cooling of the heat source. The effect of nanoparticles insertion is also shown at the temperature distribution along the substrate.

Natural convection flow in an open rectangular cavity with cold sidewalls and constant volumetric heat source

2011 ◽  
Vol 225 (5) ◽  
pp. 1191-1201 ◽  
Author(s):  
M Saleem ◽  
S Asghar ◽  
M A Hossain
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Finite Difference ◽  
Heat Source ◽  
Prandtl Number ◽  
Rectangular Cavity ◽  
Maximum Temperature ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Volumetric Heat Source

The transient two-dimensional natural convection flow of Newtonian fluid in an open rectangular cavity has been studied numerically. The flow is induced due to constant internal heat generation. The alternate direct implicit (ADI) finite difference, together with upwind finite-difference scheme and successive over relaxation method, are used to solve the non-dimensional equations numerically. Effects of Rayleigh number, Ra, Prandtl number, Pr, and cavity aspect ratio, A, on the flow patterns and isotherms as well as on the heat transfer rate are studied graphically. The maximum temperature induced due to the constant volumetric heat source is found with the increase in cavity width, and to decrease with the increase in Prandtl number and Rayleigh number. The numerical model employed here is found to be in good agreement with the previous work.

NATURAL CONVECTION FLOW ON A SPHERE THROUGH POROUS MEDIUM IN PRESENCE OF HEAT SOURCE/SINK NEAR A STAGNATION POINT

2008 ◽  
Vol 13 (4) ◽  
pp. 513-520 ◽  
Author(s):  
Sourangshu Mukhopadhyay
Keyword(s):  
Boundary Layer ◽  
Porous Medium ◽  
Natural Convection ◽  
Heat Source ◽  
Prandtl Number ◽  
Stagnation Point ◽  
Fluid Velocity ◽  
Convection Flow ◽  
Convection Boundary Layer ◽  
Source Sink

Steady natural convection boundary‐layer flow in the neighbourhood of lower stagnation point of a heated sphere embedded in a saturated porous medium in presence of heat source/sink is considered. The dimensionless governing equations for this investigation are solved numerically by shooting method. Then attention is focused on finding the effects of porosity parameter, heat source/sink parameter and the Prandtl number on velocity and temperature distributions. With the increase of permeability parameter of the porous medium, the fluid velocity decreases but the temperature increases at a particular point of the surface. Due to increasing values of heat source/sink parameter, fluid velocity is found to increase. It is noticed that the velocity boundary layer is suppressed with the increasing Prandtl number and the temperature decreases in this case. Prandtl number has an important effect in increasing the rate of heat transfer from the surface of the sphere.

scholarly journals Analysis of Heat Exchange Rate for Low-Depth Modular Ground Heat Exchanger through Real-Scale Experiment

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1893
Author(s):  
Kwonye Kim ◽  
Jaemin Kim ◽  
Yujin Nam ◽  
Euyjoon Lee ◽  
Eunchul Kang ◽  
...  
Keyword(s):  
Exchange Rate ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Pump ◽  
Heat Extraction ◽  
Ground Heat Exchanger ◽  
Pump System ◽  
Heat Pump System ◽  
Scale Experiment ◽  
Real Scale

A ground source heat pump system is a high-performance technology used for maintaining a stable underground temperature all year-round. However, the high costs for installation, such as for boring and drilling, is a drawback that prevents the system to be rapidly introduced into the market. This study proposes a modular ground heat exchanger (GHX) that can compensate for the disadvantages (such as high-boring/drilling costs) of the conventional vertical GHX. Through a real-scale experiment, a modular GHX was manufactured and buried at a depth of 4 m below ground level; the heat exchange rate and the change in underground temperatures during the GHX operation were tracked and calculated. The average heat exchanges rate was 78.98 W/m and 88.83 W/m during heating and cooling periods, respectively; the underground temperature decreased by 1.2 °C during heat extraction and increased by 4.4 °C during heat emission, with the heat pump (HP) working. The study showed that the modular GHX is a cost-effective alternative to the vertical GHX; further research is needed for application to actual small buildings.

Evaluation of heat exchange rate of GHE in geothermal heat pump systems

2009 ◽  
Vol 34 (12) ◽  
pp. 2898-2904 ◽  
Author(s):  
Liu Jun ◽  
Zhang Xu ◽  
Gao Jun ◽  
Yang Jie
Keyword(s):  
Exchange Rate ◽  
Heat Exchange ◽  
Heat Pump ◽  
Geothermal Heat ◽  
Geothermal Heat Pump
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