Sanitary Product Heating U-Tube Exchangers

Sanitary Heating
U-Tube Exchangers

Heating the Product Stream Without Damaging It

Product heating covers sauces, purees, syrups, protein solutions, dairy streams, plant-based beverages and anything else that has to reach a target temperature without being altered on the way there. The thermal duty is usually straightforward; everything around it is not.

Burn-on is the dominant fouling mechanism. Product in contact with a surface well above its bulk temperature denatures, caramelises or scorches and adheres. That deposit insulates, so the wall runs hotter, so the deposit grows faster. Run length between cleans collapses, and the cleaning itself becomes more aggressive, which shortens equipment life in turn.

Surface temperature, not medium temperature. This is the single most useful thing to get right. Using 100 psi steam to heat a delicate stream produces a wall temperature far above the product target, and the product touching that wall pays for it. Hot water or low-pressure steam with a larger exchanger costs more in surface and far less in cleaning downtime and product loss. On most sanitary heating duty that trade is strongly favourable.

Which side should the product be on? Shell side gives gentler velocities for shear-sensitive fluids and a surface you can physically reach once the bundle is out, at the cost of having to engineer drainage rather than assume it. Tube side gives a smooth passage that CIP solution follows exactly, with the U-bend as the honest limitation. Viscous products and anything carrying particulates usually favour the shell.

Viscosity is a range, not a number. Send the viscosity across the whole temperature range rather than at one point. Product entering cold and leaving hot changes its flow regime through the exchanger, and a design based on the average will misjudge both the coefficient and the pressure drop.

Particulates favour tubular. Plate exchangers block on fibres, pulp and inclusions. A tubular unit sized with passage dimensions chosen against the largest expected particle handles those streams comfortably, and the bundle can be pulled and the shell side cleaned. This is one of the clearer cases where shell and tube beats plate on sanitary duty.

Related pages: sanitary U-tube exchangers, pasteurization and HTST, sanitary product cooling and surface finish and passivation.