Plate heat exchangers thermal design

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. 

Prasad B. The thermal design and rating of multistream plate-fin heat exchangers. In Shah RK, ed. Compact Heat Exchangers for the Process Industry. Begell House, 1997 79-100. 

The distillation column was simulated and designed with the CHEMCAD-SCDS method, also using the SRK equation of state. Reflux ratio for die distillation column was set at 1.2 Rnm- Plate efficiency of the valve trays was assumed to be 0.85. (Pooling water was available with an inlet temperature of 29°C and an exit temperature of 35°C. The CC-Therm software was used for the thermal and mechanical design of all the shell-and-tube heat exchangers. 

The flow maldistribution problem in evaporators is most severe when the major part of the pressure drop occurs in the two-phase heated region and cannot be prevented in some cases (reboilers and evaporators). However, in most heat exchangers with such problems, the economic penalty for maldistribution is small, and deterioration of the thermal performance is slightly affected [115]. The flow instabilities can be controlled by restricting the liquid circulation [2], Falling film evaporators are particularly prone to flow maldistribution. This effect can be reduced through design modifications (the top tube plate must be exactly horizontal, addition of inserts into the top of each tube must be secured, etc.) [120]. 

The secondary heat exchanger is contained in a stainless steel cylinder vessel. The air pressure above the water level is 0.39 MPa. Below the eater level, the plates which are similar in design to the primary heat exchanger, are placed below the water level. The secondary heat exchanger, apart from the function of heat supply to the heating grid, performs the function of a compensator for thermal expansion of Ae secondary circuit. The diameter of the connecting pipes in the second circuit is 200 mm. 

Thermatron specialise in the design and manufacture of compact liquid to air heat exchangers and above ambient cooling systems, utilising state of the art technology such as fins and enhanced plates. Electronics thermal control is the main application area. 

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