Analysis and Optimisation of Counter Flow Heat Exchanger

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 Abstract 

The heat transfer in a simple counter flow heat exchanger was investigated through the application of Computational Fluid Dynamics (CFD). The goal of the assignment was to achieve efficient heat transfer between hot air and cold coolant, with the aim of cooling the air. The base model, utilising cold water running through a copper pipe, was simulated through the application of the k-epsilon model on ANSYS Workbench 19.1 using the commercial CFX code. The mesh created on the model predominantly consisted of tetrahedral unstructured grids and utilised 500,000 mesh elements. The simulation carried out, with set boundary conditions and a residual target of 1 × 10−4 , provided an outlet air temperature of 298.04K. However, this was sought to be ineffective as the distribution of temperature was not uniform. The base model was further simulated with various pipe materials (aluminium and steel) and coolants (methanol and acetone), and the results suggested copper and water to be the most effective in this application. Two optimisation models were then created by increasing the surface area of the pipe and the addition of baffles, which yielded improved heat transfer efficiencies with outlet air temperatures of 295.756K and 280.758K respectively.