Case Study of the effect on heat transfer enhancement in rectangular channels with triangular baffles
The thermal performance of a heat exchanger depends upon various parameters like inlet temperature of a hot fluid, type of hot fluid, type of cold fluid, shape of baffles, material of baffles, baffles angle and property of ribs. Basically fluid flow and heat transfer characteristics are largely depends upon the Reynolds number (Re). Reynolds number is basically the ratio of inertia force to viscous force. Re is only the factor by which we can decide whether the fluid is laminar or turbulent in shell and…show more content… These baffles can significantly disturb the bulk flow
Use of heat sink such as fins increases the surface area in contact with the coolant. These extended dissipation area are widely recognized to improve the heat transfer.
Various examples are plain fin, wavy fin, louvered fin, offset-strip fin, etc.
Twisted Tapes and Wire Coils
Twisted tapes are metallic strips twisted in some ratio known as twist ratio, inserted in the flow.
Wire coil inserts are made by tightly wrapping a coil of spring wire on a rod. When the coil spring is pulled up the wires forms a helical roughness.
This section includes such surface which has fin scales or coating which may be continuous or discontinuous. It also includes rough surfaces which promotes turbulence in the flow field
It involves high velocity jet to cool directly the surface of inserts. It also involves the direction of heating or cooling fluid perpendicularly or obliquely to the heat transfer surface…show more content… Special allowance changes are made for finned tubes.
The different types of baffles: Diamond Shaped baffles Z-Shaped baffles V-baffles 45° inclined baffles Porous baffles
In this experiment heat exchanger consists of rectangular channel and special type of triangular baffles having triple pass tubes.
An optimal design of a heat exchanger is triangular baffle having triple pass tube arrangement with rectangular channel largely depends on the operating conditions of the heat exchanger and can be accomplished by appropriate design of helix angle, baffle overlapping, and tube layout. The baffle angle is 5º-10º.
The steady state of the heat transfer rate is assumed to be equal to the heat loss from the test section which can be expressed as:
Qair =Qconv (1)
Where,Qair= Cp,a (To-Ti) (2)
Qconv= hA(Tw – Tb) (3)
Where, Tb = (To + Ti)/2 (4)