Heat Transfer Analysis of a Helically Coiled Heat Exchanger

Enhancing the heat transfer by the use of helical coils has been studied and researched by many researchers because the fluid dynamics inside the pipes of a heat exchangers offer certain advantages over a straight tubes, shell and tube heat exchanger, in terms of better heat transfer and mass transfer coefficients.               

After validating the methodology of CFD analysis of a heat exchanger against the numerical results available in literature, the effect of considering the actual fluid properties instead of a constant value is established. The characteristics of heat transfer inside a helical coil for different boundary conditions are compared. The flow field through the helically coiled tube is simulated by solving the appropriate governing equations: conservation of mass, momentum and energy. The turbulence is taken by Shear Stress Transport (SST) k-ε of closure.SST  k-ε has a blending function which acts as a standard k-ε in main stream flow and as standard  k-ε near the boundary layer  where the gradient is much steeper.

It is observed that the specification of a constant temperature or constant heat flux boundary condition for an actual heat exchanger does not yield proper modelling. Hence, conjugate heat transfer and temperature dependent properties of heat transport media are considered for the analysis of the heat exchanger. The CFD calculation results are obtained using the CFD package FLUENT 14.0.Since the above work necessitates the knowledge in CFD package FLUENT, a sample model of the helical coil heat exchanger is made using FLUENT before taking up the above

mentioned   project. The present report summarizes few of the studies thus made. The report also mentions the work performed with regard to the project problem.