| Popis: |
Thermal energy between two or more fluids is transferred by the Heat Exchanger. The fluids exist as single-phase or two-phase fluid. Based on the exchanger type, the fluids can be separated or it can be mixed. Heat exchangers are classified into many categories based on many factors such as flow direction, contact of fluids, shape and size of tubes, etc. The heat exchanger under consideration is a shell and tube, cross-flow, parallel tube type heat exchanger. The objective here is to maximize the overall heat transfer between the hot and cold fluid using CFD analysis and Optimization. Heat exchangers are designed in such a way that flows through individual circuits in a heat exchanger are identical, but this is not true in practical application. When analyzed, it has been found that this maldistribution of flow in conventional heat exchangers can be rectified by changing the shape of the headers of the heat exchanger. When the cross-sectional shape of the header was changed to a polygon, boundary layer of varying thickness forms across the cross-section. This causes the flow to be more evenly distributed than from the header with a circular cross-section. Upon further investigation, it has been found that the maximum flow velocity reduces when using a polygon shaped header, which again reduces the maximum heat transfer. Upon comparison, it has been found that a heat exchanger header with a regular hexagonal shape as its cross-section will yield the maximum heat transfer rate as the flow is more evenly distributed and the maximum flow velocity is maintained. |
