Views: 0 Author: Site Editor Publish Time: 2026-02-11 Origin: Site
In hospital HVAC (heating, ventilation, and air-conditioning) systems, fan-assisted dry coolers can be used to implement free cooling—an economizer-type mode where outside air and a fluid-to-air heat exchanger remove heat from a cooling loop without operating mechanical chillers. When conditions permit, this approach significantly reduces electrical energy consumption for cooling.
Free cooling refers to using outdoor ambient air to reject heat from a chilled water loop (or process fluid) instead of running chillers. For a fan-assisted dry cooler, fans move outdoor air across finned heat exchanger coils to cool fluid when the ambient temperature is below the fluid return temperature. A dry cooler with controls will modulate fans and bypass valves to maximize the period during which free cooling can meet the load.
Fan-assisted dry coolers consume much less energy than chillers because they only need fan power and fluid pumps, not high-power compressors. Typical fans—especially those with electronically commutated (EC) motors—can operate with high electrical efficiency and variable speed control to match load demand, further reducing consumption.
EC fans often achieve 85–92% motor efficiency with full variable-speed control, lowering energy use compared with traditional AC fans.
The energy benefit depends strongly on how many hours ambient conditions allow free cooling to meet demand. In climates where outdoor dry-bulb temperatures are sufficiently below the chilled water return temperature for long periods, hospitals can rely on free cooling extensively. Manufacturer and third-party analyses indicate:
Free cooling savings typically range from ~30% to 80% of cooling energy relative to a chiller-only baseline, depending on local climate, system design, and free cooling hours.
For temperate climates, savings tend toward 50–65%, while cold climates with long free-cooling seasons can approach 70–80%.3. System-Level Efficiency
When a dry cooler is integrated as a separate free cooling unit (not as an integrated chiller coil), it avoids derating chiller performance and allows continuous optimal airflow paths. This tends to yield net energy benefits, albeit modest in light-load applications.
Such separation avoids system interactions that can reduce chiller efficiency in low-load periods—important in hospitals where cooling demand may be lower in cooler seasons.
In cooler locations, free cooling hours can be frequent, so the dry cooler can assume most of the cooling load for extended periods. In such cases, annual electricity use for cooling can drop substantially, as compressors sit idle.
Hospitals installing free coolers have reported significant energy and CO₂ reductions, with measurable electrical savings (e.g., substantial reductions in chiller run-hours and near-annual operational energy decreases).
Because dry coolers reduce chiller runtime and electrical load, they often yield short to moderate payback periods, particularly where free-cooling hours are abundant. Maintenance costs are relatively low since these units do not rely on evaporative water contacts and have no refrigerant compressors.
Free cooling efficiency is optimal when outdoor temperatures are significantly lower than setpoints (e.g., 5–10°C below return fluid temperature). Even modest differential enables
partial free cooling.
Advanced controls that optimize fan speed and bypass valves reduce unnecessary fan energy and extend free-cooling periods.
Fan-assisted dry coolers are an energy-efficient component for free cooling in hospital HVAC systems, especially in climates with extended periods of cool outdoor air. Key efficiency attributes include:
Low operational power (fans and pumps only) compared with chiller compressors.
Substantial energy savings (30–80% reduction in cooling energy use) where ambient conditions permit free cooling.
Improved system performance when properly controlled and integrated without derating existing chiller equipment.
