SWEP BX8T

SWEP publishes a channel volume of 0.039 liters per channel, the same on both sides. Total hold-up is that figure times the number of channels on each side, and we give it with the quote for the plate count in question.

On refrigerant duty the hold-up sets how much charge the exchanger takes, and a small volume helps keep the system charge down. It also means the unit responds quickly: little fluid and little metal, so outlet temperatures follow load changes almost immediatly and the controls have to keep up. The same small volume on the water side is why a BX8T freezes fast if flow stops.

By SWEP's formula a 30-plate BX8T is about 2.8 kg (6.1 lb) and a 60-plate unit about 5 kg (11 lb), empty.

That is light enough to tempt installers into letting the pipes carry it, and it should not be done. In container refrigeration the unit sees constant transport vibration on top of compressor pulsation, and an unsupported exchanger turns its connections into the flex point; the braze joints there are what fatigue. Clamp the body in a bracket, support the lines close to the unit, and leave the connections carrying no load. Mounting and Piping has the details.

SWEP publishes PED, UL and KHK for the BX8T - the European pressure equiptment approval, the North American recognition and the Japanese high-pressure gas approval.

The approval is only half the check; the pressure class is the other half. The catalogued BX8T part numbers on file are class S, a category of 31 bar at 155 C that covers a wide variety of applications. Refrigerants such as R410A are normally matched to class M, up to 45 bar at 135 C and fatigue tested. Tell us the refrigerant, and copy the class letter from the old nameplate exactly. Pressure Classes explains the letters.

The catalogued designations on file are, for example BX8THx30/1P-SC-S. One pass means each fluid crosses the pack once, with all four connections on the front.

Multi-pass builds exist across brazed plate exchangers for duties that need a longer thermal path than one trip up a short plate can give. The trade is higher pressure drop and connections on the rear cover as well as the front. On a frame limited to 60 plates and 17.61 GPM, that pressure drop arrives early, so check it against the pump before choosing multi-pass over more plates.

Too small, and pressure drop is the first symptom: flow falls short, the approach opens, and a heat pump runs at a higher condensing or lower evaporating temperature than it should. The frame tops out at 60 plates, so a duty that needs more than that belongs on a larger frame, not a BX8T pushed to its 17.61 GPM port ceiling.

Too large is less obvious. Velocity in each channel drops, the water side fouls sooner, and on evaporating duty the refrigerant distributes unevenly at part load, which shows as unstable superheat. Size to the real duty and fluid, not to the next plate count up.

These models are catalogued alongside the BX8T. Each has its own page with its dimensions, materials and part numbers.

SWEP B8T - Nickel-brazed - the copper-free option at small size, for ammonia and aggressive media.

SWEP B8DW - The most compact double-wall brazed plate heat exchanger in the SWEP range.

SWEP B8LAS - Compact AsyMatrix brazed plate heat exchanger pairing high thermal performance with low pressure drop.

SWEP E8AS - AsyMatrix brazed plate heat exchanger on the B8T frame, used mainly for heating tap water.

SWEP E8LAS - AsyMatrix brazed plate heat exchanger on the B8T frame for the highest thermal demands in tap water.

SWEP E8T - A compact copper-brazed plate heat exchanger for wall-hung, non-condensing boilers.