Plate heat exchangers pressure drop

These curves provide a comparison of heat transfer rotes for plate heat exchangers and shell and tube equipment. The values given ore typical for pressure drops shown and ore based upon the thermal characteristics of the fluids. 

Typical velocities in plate heat exchangers for waterlike fluids in turbulent flow are 0.3-0.9 meters per second (m/s) but true velocities in certain regions will be higher by a factor of up to 4 due to the effect of the corrugations. All heat transfer and pressure drop relationships are, however, based on either a velocity calculated from the average plate gap or on the flow rate per passage. 

The plate heat exchanger, for example, can be used in laminar flow duties, for the evaporation of fluids with relatively high viscosities, for cooling various gases, and for condensing applications where pressure-drop parameters are not excessively restrictive. 

For those condensing duties where permissible pressure loss is less than 0.07kpf/cm there is no doubt but that the tubular unit is most efficient. Under such pressure-drop conditions only a portion of the length of a plate heat exchanger plate would be used and a substantial surface area would be wasted. However, when less restrictive pressure drops are available the plate heat exchanger becomes an excellent condenser, since very high heat transfer coefficients are obtained and the condensation can be carried out in a single pass across the plate. 

Higher overall heat transfer coefficients are obtained with the plate heat exchanger compared with a tubular for a similar loss of pressure because the shell side of a tubular exchanger is basically a poor design from a thermal point of view. Considerable pressure drop is used without much benefit in heat transfer efficiency. This is due to the turbulence in the separated region at the rear of the tube. Additionally, large areas of tubes even in a well-designed tubular unit are partially bypassed by liquid and low heat transfer areas are thus created. 

It can be seen that for heat transfer, the plate heat exchanger is ideal because the value of d is small and the film coefficients are proportional to Unfortunately, the pressure loss is proportional to and pressure drop is sacrificed to achieve the heat transfer. 

A note of caution on the use of photo-etched channels has been offered by RAMSHAWfl3 ) who points out that the system is attractive in principle provided that severe practical problems such as fouling are not encountered. With laminar flow in matrices with a mean plate spacing of 0.3-1 mm, volumetric heat transfer coefficients of 7 MW/m3 K have been obtained with modest pressure drops. Such values compare with 0.2 MW/m3 K for shell and tube exchangers and 1.2 MW/m3 K for plate heat exchangers. 

Kreissig G, Muller-Steinhagen HM. Frictional pressure drop for gas/liquid two-phase flow in plate heat exchangers. Heat Transfer Eng 1992 13(4) 42-52. 

Here the + sign denotes vertical upflow (i.e., pressure drop), the sign denotes vertical downflow (i.e., pressure rise or recovery). The first three components of the core pressure drop are now presented for plate-fin, tube-fin, regenerative, and plate heat exchangers. Pressure drop on the shellside of a shell-and-tube heat exchanger is presented in Table 17.31. 

Plate Heat Exchangers. Pressure drop in a plate heat exchanger consists of three components (1) pressure drop associated with the inlet and outlet manifolds and ports, (2) pressure drop within the core (plate passages), and (3) pressure drop due to the elevation change. The... 

Sulphur melters and burner, water treatment plant internal, heat exchangers between converter passes (de-scaling of tubes), plate heat exchangers for acid and oleum cooling. Special emphasis is laid on those units having abnormal pressure drops and less efficiency (converter, acid towers, heat exchangers, etc.). 

The channels of most plate heat exchanger/reactors are switched in parallel, which reduces the pressure drop compared to alternative flow patterns such as serpentine flow fields. However, flow equipartition is crucial for parallel flow arrangements. It is achieved by perforated plates [89] when a whole stack of plates is fed in parallel from the plate front. Such pinhole plates create additional pressure drop. In case the feed gas is distributed to each plate first and then by a dedicated inlet section to each channel of the plate, a sophisticated geometry of this inlet section [90] helps to achieve flow equipartition. An alternative is the variation of the channel width over the reactor length axis [91]. 

Tube pass Tube pass is a tool for heat exchanger designer to control the tube side velocity, pressure drop, and heat transfer, F.achtime tube side fluid flows from one head to the other is counted as one pass. For countercurrent flow heat exchanger, it has one tube pass and one shell pass. If tube side flow is low or there is enough allowable tube side pressure drop, tube pass should be Increased to increase tube side velocity and heat transfer. For tube pass mote than one, partition plates are required at inlet and outlet heads to direct the tube side fluid flow. 

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