The plate channels of a diffusion-bonded plate heat exchanger are formed by diffusion bonding two plate blanks and then hydraulically bulging them; the channel shape is directly related to the medium characteristics. When submitting selection data, the medium name, volumetric or mass flow rate, inlet and outlet temperatures, and allowable pressure drop for both the hot side and cold side should be provided, and it should be noted whether the medium contains particles, is corrosive, or tends to foul. For media with high solids content, the particle size distribution should also be stated so that the channel width and flow direction arrangement can be determined. If allowable pressure drop data are missing, the calculation results may deviate from the actual capability of the on-site pump system.
Once the parameters are complete, estimate the single-channel flow velocity based on the medium flow rate and allowable pressure drop, then determine the number of parallel channels and the pass arrangement. For media with higher viscosity, wider channels and lower flow velocities should be used to avoid exceeding the permitted pressure drop; for operating conditions with large temperature differences, the thermal stress of the plates must be checked, and if necessary, a multi-pass arrangement should be used to balance the heat transfer area on both sides. During the selection stage, the connectability of the nozzle orientation with the on-site piping should also be checked, and maintenance space should be reserved.
The plate material is selected according to the corrosiveness of the medium, and the sealing parts in contact with the medium must be compatible with the plate material. For fouling-prone conditions, chemical cleaning connections can be reserved during design; cleaning agents should be used after dilution according to the instructions to avoid reactions with the plate material. Before equipment that has been out of service for a long time is put back into operation, the insulation resistance should be measured; if it is below the specified value, the equipment can be dried in an oven at about 200°C, or energized at a reduced voltage for heating until the insulation resistance recovers.
After selection is confirmed, check the connection specifications, design pressure and test pressure, plate material certificates, and channel arrangement drawings. During on-site installation, ensure that nozzle loads are not transmitted to the plate pack; during initial operation, record the inlet and outlet pressure drops as criteria for subsequent cleaning.
