Shell as it moves fluid across the temperature gradient.

Shell
and helical coiled tube heat exchangers are known as the most common sort of
heat exchangers due to their compactness, ease of manufacture and heat transfer
efficiency. Shell and helical coil heat exchanger is preferred over other
conventional heat exchanger due to its ability to transfer more heat in given
space limitation. The coil curvature provide centrifugal forces to act on the
fluid flowing inside heat exchanger, which result in secondary flow pattern
which is perpendicular to the axial flow pattern. This secondary pattern
consists of two vortices. Heat transfer rates are increased by secondary flow
as it moves fluid across the temperature gradient. Hence, there is an
additional convective heat transfer mechanism that is perpendicular to the
axial flow, which does not exist in straight tube heat exchangers.

Several
researchers have analyzed the helical coil heat exchangers, which involves
various dimensionless numbers and geometric parameter variation in order to
improve the heat transfer rate and effectiveness of heat exchanger and some
studies are focused towards either constant wall temperature or constant wall
heat flux boundary conditions of heat exchanger. However some studied are
focused on the effect of air bubble injection into helical coil heat exchanger,
the variations of NTU and effectiveness due to the air bubbles injection with
different air flow rates.

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In
last few years more computational methods have been developed as technological
advancement. These computational methods helped researchers in analyzing
combustion, fluid dynamics and behaviour of different models of heat transfer
etc. the heat exchangers have wide range of applications in various industries,
which have attracted more researchers to work in this field.

Following
articles presents a review of important published literature:-

 

2.1.        
Previous work

Austen
et al. (1988) Studied the influence of pitch on the
pressure drop and heat transfer characteristics of helical coils is explored
for the condition of uniform input heat flux. Two pairs of coils were tested;
each pair corresponds to the same diametric ratio but substantially different
pitch ratio. Water (3