In our 35 years of manufacturing tube and plate heat exchangers at Teralba Industries, we are often asked how plate heat exchangers compare to tubular units. So we have sought to provide a transparent assessment of the Pros and Cons of both types.
PHE,s are typically more efficient than tube-in-tube heat exchangers as the deep chevrons on the heat transfer plates create significant turbulence and, therefore, a high heat transfer coefficient. That said, recent advances in tubular heat exchanger technologies, such as deep dimples or corrugations on the inner and outer tubes, to radically increase turbulence have narrowed the gap.
This is one area where tube heat exchangers outperform plate heat exchangers every time. The large cross-sectional area of tubular heat exchangers means that viscous slurries, particulate-laden fluids, and non-Newtonian products can be heated or cooled easily. Products such as dips, chutney, fruit yoghurt and, in industrial environments, sewerage; can be heated or cooled without blockages.
PHE,s can only tolerate clear fluids or, at best, very small particles and low-viscosity liquids.
Plate Heat Exchangers usually occupy a much smaller footprint than tube heat exchangers. Depending on the application and heat transfer area required, a tube HE with horizontal tubes may take up to 5 or 5 times the floor area of a PHE. However, in some applications where drainability is unimportant, be mounted vertically to minimise footprint size.
By their inherent design, Plate PHE,s won’t drain or are difficult to drain, especially on multi-pass configurations. Tubular heat exchangers with dimpled tubing can be configured to be completely free draining. Hence their use in the pharmaceutical industry.
Plate exchangers use a peripheral gasket and port hole gasket to seal each heat exchanger plate from the next. These gaskets need replacing periodically. EPDM or VITON gaskets would be replaced on high-temperature applications every 12 – 36 months, depending on the application. The heat transfer plates are typically 0.5mm or 0.6mm thick stainless steel, compared to 1.6mm – 4mm thick tube walls. Tubular HE,s will mostly outlast a plate unit. Tube heat exchangers usually have gaskets exclusively on the inlet and outlet connections and require virtually no maintenance.
As tube exchangers are larger for any given duty than a plate unit, the initial purchase price is usually higher. However, the lifetime cost must be considered as the PHE requires downtime and parts for maintenance. Another consideration is, are future changes in product possible? A food or beverage manufacturer may want to add fruit pieces for a new product range. These can only be heated or chilled through a tube heat exchanger.
So which heat exchanger is best?
It comes down to “horses for courses”.
Clear fluids such as milk, beer, and water are nearly always processed through plate heat exchangers and thick products or waste streams, including liquids with chunks or particles, and very high-temperature applications use tube heat exchanger designs.