20-11-2012, 06:12 PM
EXPERIMENTAL HEAT TRANSFER ANALYSIS ON ANNULAR CIRCULAR AND ELLIPTICAL FINS
EXPERIMENTAL HEAT TRANSFER.pdf (Size: 850.1 KB / Downloads: 101)
Abstract:
Most of the engineering problems require high performance heat transfer components with progressively
less weights, volumes, accommodating shapes and costs. Extended surfaces (fins) are one of the heat exchanging
devices that are employed extensively to increase heat transfer rates. The rate of heat transfer depends on the surface
area of the fin. Radial or annular fins are one of the most popular choices for exchanging the heat transfer rate from
the primary surface of cylindrical shape. In this paper the heat transfer rate and efficiency for circular and elliptical
annular fins were analyzed for different environmental conditions.. Elliptical fin efficiency is more than circular fin.
If space restriction is there along one particular direction while the perpendicular direction is relatively unrestricted
elliptical fins could be a good choice.
Introduction:
Finned tube heat exchangers are widely used in many industrial applications such as, air conditioning,
chemical processing systems, Heat exchangers for refrigeration and in storage tanks of waste nuclear materials etc.
In general the augmentation of heat transfer from tubes carrying stream of hot fluid to the surrounding cold gases is
attainable by attaching arrays of annular fins to the outer surface of the tubes.
The selection of any particular type of fin depends mainly on the geometry of this
primarysurface.Radial or annular fins are one of the most popular choices for enhancing the heat transfer rate from
the primary surface of cylindrical shape. It is well known that the rate of heat transfer from the fin decreases with the
increase of fin length and hence, the entire heat transfer surface of a fin may not be equally utilized. For this reason,
there is a continuous effort by the designers to determine the optimum fin that will maximize the rate of heat transfer
for a specified fin volume or minimize the fin volume for a given heat transfer.
Problem definition:
Now a days compact heat exchanger with less weight, cost and space are required in food processing
industries, chemical industries and refrigeration units. From [3]space restriction on one side and enough space in
perpendicular directions elliptic fins will be better choice .
Experimental analysis:
Fig 2a and 2b are the schematic diagram of the experimental apparatus used in the present study
for the estimation of heat transfer on annular fin at one tube. The various dimensions required for the setup are
taken from the reference (8). The annular circular and elliptical fin made of aluminum is vertically mounted on
the circular tube. The circular fins have the outer diameter of 99mm ,thickness 1mm and the space between the fin
is 5mm . The horizontal circular tube is placed on two supports which is 98 mm above the experimental table to
avoid ground effect. Length, diameter and thickness on the horizontal circular pipe made of aluminum are
400mm,32mm and 3mm. Electrical heating coil with 0.5 kW capacity is kept inside the tube. Size of the box is
500x300x300mm . Thermal conductivity of aluminum is 237 W/mK.
Conclusion:
In present work the rate of heat transfer from elliptic fin circumscribing circular tube was analyzed by
experimental method. Fin efficiency is higher for elliptical fin than circular fin.
If space restriction is along one particular direction, while the perpendicular direction is relatively unrestricted
elliptic fins could be a better choice.
Normally heat transfer co-efficient depends upon the space ,time , flow conditions and fluid properties. If there
are changes in environmental conditions, there is changes in heat transfer co-efficient and efficiency also.