(1)Plate type selection
The plate type or corrugated type should be determined according to the actual needs of the heat exchange occasion. For the case where the flow rate is large and the pressure drop is small, the plate type with low resistance should be selected, and the plate type with large resistance should be selected. Depending on the fluid pressure and temperature, it is determined whether the detachable or brazed type is selected. When determining the plate type, it is not suitable to select the plate with too small a single plate area, so as to avoid too many plates, the flow velocity between the plates is too small, and the heat transfer coefficient is too low. This problem should be paid more attention to the larger heat exchanger.
(2) Process and flow path selection
The process refers to a set of parallel flow channels in the same flow direction of a medium in a plate heat exchanger, and the flow path refers to a medium flow channel formed by two adjacent plates in a plate heat exchanger. In general, several flow passages are connected in parallel or in series to form different combinations of cold and heat medium passages.
The process combination should be calculated based on heat transfer and fluid resistance and determined under the requirements of the process conditions. Try to make the convective heat transfer coefficient in the cold and hot water flow channels equal or close, so as to get the best heat transfer effect. The heat transfer coefficient obtains a larger value because the convective heat transfer coefficients on both sides of the heat transfer surface are equal or close. Although the flow rates between the plates of the plate heat exchanger are not equal, the calculation is based on the average flow rate in the calculation of heat transfer and fluid resistance. Since the "U"-shaped single-flow nozzle is fixed on the pressing plate, the disassembly and assembly is convenient.
(3)Pressure drop check
In the design and selection of plate heat exchangers, there is a certain requirement for pressure drop, so it should be checked. If the check pressure drop exceeds the allowable pressure drop, the design selection calculation must be repeated until the process requirements are met.