چكيده به لاتين
The performance of the heat exchanger is enhanced by using increasing heat transfer methods. Flat spiral heat exchanger has many applications, due to advantages such as simple structure, high heat transfer efficiency, low maintenance cost, smaller occupied area, etc. Radial component of velocity is created under the influence of centrifugal forces in the spiral passage, as the way that the flow in the outer part of the pipe moves faster than the inner part, and this velocity difference creates the secondary flow. Therefore, while reducing the size of the heat exchanger, curved streamlines increase the momentum rate and heat transfer coefficient.
In this thesis, considering water as the base fluid, heat transfer, pressure drop, friction coefficient, porosity and performance evaluation criteria parameters for laminar flow, are numerically simulated in a flat spiral heat exchanger. The governing equations have been solved using the computational fluid dynamics method with the fluent software and in the Reynolds number range of 500 to 2000. The solver scheme is the coupled algorithm and equations are solved by the second order and pseudo transient method.
After validating the numerical solution method in comparison with the experimental results in the basic article, the effect of geometric parameters and flow characteristics (including the number of rotations of 3, 4, 5 and 6 cycles, Reynolds numbers 500, 1000, 1500 and 2000, adding porous media with porosity coefficient 0.9 and Darcy numbers of 0.1, 0.01, 0.001 and 0.0001) on heat transfer characteristics and pressure drop has been studied. The performance evaluation criteria shows that the use of six cycles and the addition of a porous medium with a Darcy number of 0.1 at Reynolds 500 affects the improvement of the heat transfer process by 615% and this method can be used in experimental applications.
