Design method of plate heat exchanger using the mean temperature difference method

1. Calculate the unknown temperature or flow rate, and deduce the unknown temperature or flow rate through the heat balance equation, and also deduce the heat load Q.
2. Select the appropriate plate model. Choose the appropriate plate model based on the heat exchange and flow rate.
The choice of plate type depends on the specific operating conditions. When the flow rate is large and the pressure drop is low, a plate type with low resistance should be selected; conversely, a plate type with a slightly higher resistance coefficient can be selected.
3. Estimate the heat exchange area and calculate the approximate heat exchange area based on the amount of heat exchange.
4. Select the flow path and number of channels. Initially select the flow path and number of channels for cold and hot fluids, and calculate the flow rate accordingly.
5. Calculate the average temperature difference.
6. To determine the convective heat transfer coefficient and the overall heat transfer coefficient, first calculate the convective heat transfer coefficients of the cold and hot fluids respectively, and then calculate the overall heat transfer coefficient.
7. Calculate the required heat exchange area.
8. Go back and recalculate the heat exchange area.
9. Examine the pressure drop. The allowable pressure drop is often a limiting factor in the design of plate heat exchangers. An efficient design always requires maximizing the allowable pressure drop. If, no matter how the flow arrangement is changed, the relationship between heat exchange load, flow rate, and allowable pressure drop cannot be coordinated, an inefficient design can only be implemented. If a satisfactory design cannot be obtained throughout the design process, changing the plate type can be considered.