SWEP B12

The strings on file run from 14 to 70 plates, against a frame maximum of 111. More plates means more surface and more parallel channels, so the approach closes and the pressure drop falls. On a dual-circuit build the plates are shared between the circuits, so a given count goes less far than it would in a single-circuit unit.

Plate count is not the only lever on this frame. The catalogued strings include both H and L plates at the same count, B12Hx30 and B12Lx30 for example. H gives high heat transfer at high pressure drop, L the reverse. A selection that fails on pressure drop is sometimes better fixed by changing the plate letter than by adding ten plates.

Undersized, it runs with a wide approach and a pressure drop the pump was not sized for. On a chiller circuit that reads as a leaving temperature that drifts up under load.

Oversized, the trouble is at part load. Channel velocity drops, the flow distributes unevenly through the pack, and control becomes erratic because a small change in flow produces a large change in outlet temperature. Fouling follows the low velocity. Size to the real duty with a stated fouling allowance, not a round-up on plate count.

When the pressure drop at your design flow cannot be brought inside the pump's allowance by adding plates or changing plate type. The 74.41 GPM (16.9 m3/h) figure is the ceiling set by the ports. A duty that runs near it spends much of its pressure drop in the ports instead of across the heat transfer surface.

The same applies in reverse. If a B12 selection needs far more plates than the 14 to 70 on file to meet a thermal duty at a modest flow, the plate is too short for the job, and a taller frame will do it with less metal.

Dry weight is 0.116 kg (0.256 lb) per plate, so a 70-plate unit is about 8.1 kg (17.9 lb). Add the contents: at roughly 0.06 dm3 per channel, the 69 channels of that unit hold about 4 liters between the two sides. The installed weight is what the bracket has to carry.

That is too much to hang from its connections. Support the body from below or with a strap around the pack, and anchor the pipework separately so thermal growth in the lines is not pushed into the ports. Mount it upright with the connections horizontal. On a dual-circuit build this matters more, because more pipes are pulling on the same cover plate. See Mounting and Piping.