Supermarket CO2 Systems

Standstill. A subcritical or cascade exchanger selected on its running pressure, in the tiers up to 56 or 60 bar at 100 C, is correct while the plant operates. When power fails and the store warms, the CO2 in that section warms with it and the pressure rises far past the running figure.

Either the section is protected by relief and a standstill strategy that keeps it inside the tier, or the exchanger has to be rated for what it will actually see. Decide which at design, and state it with the enquiry.

Above the critical point the CO2 does not condense at a fixed temperature; it cools continuously along the whole plate. So the figure that matters is how close the leaving gas gets to the entering water or glycol, and counter-current piping is essential to reach it.

For heat reclaim, the hottest part of the gas is the valuable part. Staging two exchangers in series - the first on hot water, the second on lower-grade heating or rejection - recovers more useful heat than one large pack. Send the ambient range and the reclaim temperatures you want.

No. U class spans 64 to 140 bar, so two units of the same frame can carry different stamped ratings. Read the design pressure and temperature off the nameplate along with the full designation, including plate count and connections.

The rating feeds straight into the safety devices. Under UL approval, each side has a relief valve set at 0.9 times design pressure, so a replacement with a different design pressure means revisiting the valves. Keeping the same rating keeps them unchanged. The SWEP B185 page lists the configurations.

It needs checking against the rating, not just the braze. The top CO2 tier is up to 140 bar at 135 C, and transcritical discharge gas can run hot when ambient is high and the compression ratio rises. The 135 C figure is reached well before the copper braze ceiling of roughly 185 C, so it is the binding one.

Give us the highest discharge temperature the rack reaches in summer operation, not the design-point value. See Pressure Classes for how pressure and temperature pair up.