Introduction

Plate heat exchangers (PHE) are widely used to transfer and recover heat from hot and cold fluid streams. This hot and cold fluid streams may be gases or liquids. Due to their clever design with closely packed metallic plates, they provide a large surface area for these fluids to interact and exchange the heat effectively. The thickness of the this plate are varies from 0.3 mm to 0.7 mm. This internal plate also comes with different designs and shapes. The whole purpose is to increase surface area and hence the heat transfer rate. 

This makes plate heat exchangers (PHE) the preferred choice when process engineers aim for a compact heat exchanger design with effective heat transfer capabilities. In the present case study, CFD analysis of plate heat exchanger is employed to resolve industrial issue and serve optimal engineering design.

Background

Our costumer has air to air plate heat exchanger (PHE) which aimed to recover heat from the exhaust gas stream and to heat the incoming fresh air.  The PHE has frequent blockage and results into clogging and shut down operation for cleaning. This was due to exhaust hot gas contain small amount of fine product particle along with high humid air. It was obvious when exhaust gas cool down below dew point, water get partially condensed and solid powder particle start depositing on the plate surface which reduce the heat transfer efficiency and cause blockage at small channels.  The operating plant facility approached us to conduct a CFD analysis to resolve this problem using CFD analysis and optimize the design to improve its performance.

Approach

The existing design of the air to air plate heat exchanger was modeled in a CFD software and a steady-state simulation was performed to evaluate the flow and temperature distribution. The simulation results were validated against the experimental data obtained from the costumers facility.

After the validation, several design modifications were proposed, including changes to the plate geometry, plate spacing, and the angle of the plates. The modified designs were then simulated using CFD to evaluate the heat transfer performance and pressure drop. The feasible provision also provided for periodic cleaning of plate heat exchanger without break down operation.

Results and Conclusion

The simulation results showed that the modified designs improved the heat transfer efficiency by up to 20% compared to the original design and also solved the problem periodic lockage and high pressure drop consumption. The pressure drop across the modified designs was also reduced significantly. The feasible provision also provided for periodic cleaning of plate heat exchanger without utilizing break down time. The optimized design was then recommended to the manufacturing facility for implementation.

The CFD analysis proved to be a useful tool in optimizing the design of the air to air plate heat exchanger. The modifications proposed by the CFD analysis improved the heat transfer efficiency and reduced energy costs for the manufacturing facility. CFD analysis for such system need special pre-CFD treatment and meaningful CFD assumption to break down this problem into simple physics with less mesh element counts to provide results within time frame.