A logistics hall cooled by water in a dry climate

Sunbelt is an insulated metal hall on Phoenix's year — 25 m² of skylight, 20 kW of day gains, a 28 / 15 °C band with a setback — on three two-stage evaporative units: a water coil cooled by a small tower pack on its own fan and pump, then a direct pad on its own sump, then a 5 m³/s supply fan, 100 % outside air. Three units are about 3.4 air changes, the low end of what such installations are sized at.

The units lead, on fan AUTO; a gas rooftop sits behind them for winter nights and the hottest afternoons. The pad's sump matters: plumbed into the tower loop, as the app's template once was, it ran as a water cooler on 25 °C water and supplied 27 °C air into a 28 °C hall.

On Phoenix's year the hall reads 536 MWh of evaporative coil duty for 52.9 MWh of fan-and-pump electricity — most of the duty is the 40 °C outside air the units bring in and cool, not the room's load — with the rooftop adding 10.9 MWh of DX trim and 1.6 MWh of gas, and 0 unmet hours in the hall and the office. The hall's 1 045 hours above 0.012 kg/kg are what evaporative cooling is.

What it reads on Phoenix

What it taught

• A direct pad on its own sump is adiabatic; on tower water it is a water cooler, which is a different machine.
• Fan AUTO is the thermostat's switch: a unit that is not the rooms' outside air should not ventilate an empty hall on ON.
• A machine with nothing to heat with derives an off stage for winter, or it blows 5 °C air into the hall at 15 m³/s.

The machines

• Example two-stage evaporative unit, 5 m³/s — open in the builder
• Example packaged rooftop with gas furnace, 4 m³/s — open in the builder
• Example DX split, 12 kW class — open in the builder

Sources

• Munters CELdek 7090/7060 published effectiveness curves
• DOE Commercial Prototype Building Models — Warehouse (shift schedule)
• PVGIS TMY, Phoenix

Readings of the shipped model on the building's own PVGIS typical meteorological year; engineering estimates from catalog data and published correlations. The building runs on every plan, including Free, a few times a day.