Thermal Sizing

The driving temperature difference shrinks as the approach tightens, and required area climbs steeply as that difference narrows. Plate units handle close approaches better than most constructions because the flow is true counterflow, but each step tighter still costs surface and pressure drop. Ask for the approach the process really needs, and let us show you the area at a slightly wider one for comparison.

Passes raise velocity on a side with low flow, which lifts the coefficient when one stream is much smaller than the other. The cost is higher pressure drop and connections on the movable end, which means disconnecting pipe to open the pack. We use passes where a single pass would leave channels underloaded, and we tell you when the trade is not worth it.

Give viscosity at two or more temperatures across the operating range, or the fluid name and concentration if it is a standard medium such as glycol. Viscosity changes so much with temperature that a single value at room temperature can misstate the cold end of the unit badly. For non-Newtonian products, say so and describe how the material behaves when pumped or stirred.

Confirm the inlet temperatures and flows match the data you sent, that the pressure drop on each side fits your pumps, and that the margin over the clean requirement matches the fouling you expect. Look at channel velocity too, since a low figure warns of faster fouling. If anything differs from your information, ask before approving rather then after delivery.