Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Forced Convection


Optimization of Microchannel Geometries to Enhance Convection Cooling of Parallel Plate Duct Flow

Faris A. Badawy

Engineering and Technology Journal, 2014, Volume 32, Issue 1, Pages 46-62

Forced convection heat transfer from arrays of microchannels was considered for fixed volume and fixed pressure drop constraints. Order of magnitude relationships were developed for the optimal dimension of a number of fundamental duct shapes including the parallel plate channel with rectangular,square, rhombus, isosceles right triangle, circular duct and elliptic duct. Using the exact analysis method to produce an approximate expression for the optimal duct shape was developed for all ducts considered. Where approximate analytical results show that the optimal shape is the parallel plate channel duct array but with
addition a triangular or rectangular duct to the parallel plate, where the rectangular model give a percent of (52%) increasing in the heat dissipation higher than the circular at an aspect ratio about (b/a=0.4), while give a percent of increase about (87%) in the same aspect ratio compared with rhombus duct model in heat dissipation due to their ability to provide the most efficient arrays in a fixed volume. Comparison of the approximate results with exact results from the
literature show excellent agreement for the optimal duct dimensions.

Study of Heat Transfer from a Sphere Body to Flowing Media

Hassanain Ali Jabber; Balasim Ahmed Abid; Abdullah Abbas Kendosh

Engineering and Technology Journal, 2008, Volume 26, Issue 12, Pages 1439-1450

In the present research the convective heat transfer from a hollow copper sphere
(10.2 cm in diameter) to air is studied at different temperatures of sphere surface.
The experiments were carried-out in an experimental channel (245 x 48 x 50 cm)
and the velocity of air was changed by varying the orientation of the gate of the
channel which has four levels. A fan of moderate capacity generates air into the
channel.
The sphere was heated by hot water at approximately constant wall at different
measured temperatures 40, 50, 60, 70 and 80 0C and local heat transfer coefficients
were calculated. This process was done by placing ten thermocouples into the inner
surface of sphere. These thermocouples were connected to a digital reader which
gives the instantaneous temperature of a specified region. The thermocouples were
numbered and distributed in an equal angular displacement of 36 degrees.
The determination of heat transfer coefficient was done through two regions, the
first called the front region, which faces the fan, and the second called the wake or
backward region in which vortices were generated and built-up. A variance of
temperature was recognized between these two regions in such a way that front
heat transfer coefficient was higher than that for backward region.
The analysis of the present work is based on Reynolds number which is change
from 12894 to 33282 depends on the velocity of the used fan. The experimental
results of this study were compared with Kendoush analytical correlation (1995)
together with a number of certain other mathematical equations obtained from the
literature. It was found that this comparison was good especially at higher
temperatures.