Numerical simulation of flow-through heat exchanger having helical flow passage using high order accurate solution dependent weighted least square based gradient calculations

Improving the fluid flow and heat transfer characteristics of a heat exchanger has always been desired for any heat transferring application. Various active, passive, and combined methods were adopted for heat transfer improvements by different heat exchangers. Here, an investigation on an annulus heat exchanger having a helical flow passage - known as a helixchanger is presented. A continuous helical fin is inserted in an annulus region which forces the fluid to flow in a helical manner. This helixchanger is planned to be used as a part of the absorber in a solar-assisted vapor absorption refrigeration system. In this paper, a high-order accurate numerical simulation of the three-dimensional flow through a helixchanger is presented. Three-dimensional Navier-Stokes equations for unsteady incompressible flows are written in artificial compressibility formulation. The convective fluxes at the cell interface are estimated using Harten Lax and van Leer with Contact for artificial compressibility Riemann solver. The high order accuracy over unstructured meshes is obtained by finding the gradient using solution-dependent weighted least squares approach. The flow-through helixchanger is simulated for various Reynolds numbers (Re = 1500-6500), corresponding pressure drop, and the average heat transfer coefficient is presented. It has been observed that, due to the helical flow path, the flow becomes naturally turbulent, thereby helping in increasing heat transfer. The experimental setup is also developed, and the numerical results are validated against the experimental results. A correlation is also proposed for the heat transfer through the helical flow path.