The heat path
Servers turn almost all electrical power into heat. Cooling design is about moving that heat from chip to server air, from server air to room air, from room air to chilled water or refrigerant, and finally out of the building. Every inefficient step increases power use.
In a well-run hall, cold supply air reaches equipment inlets without mixing with hot exhaust air. Hot exhaust returns to cooling units at a high enough temperature for efficient heat transfer.
Airflow and containment
The basic layout is hot aisle / cold aisle: server fronts face cold aisles, server backs face hot aisles. Containment improves this by physically separating cold supply and hot return air. It can be cold-aisle containment, hot-aisle containment or room-level containment depending on the hall.
Blanking panels, brush grommets, cable management and floor sealing matter. A missing blanking panel or open floor tile can waste cooling by letting air bypass equipment.
Common cooling systems
| System | How it works | Best fit |
|---|---|---|
| CRAC | Computer room air conditioner with refrigerant-based cooling. | Smaller rooms and legacy spaces. |
| CRAH | Air handler using chilled water coils. | Larger halls with central chilled-water plants. |
| In-row cooling | Cooling units placed between racks. | Medium density zones or retrofits. |
| Rear-door heat exchanger | Liquid-cooled door removes heat from rack exhaust. | High density retrofit where servers remain air-cooled. |
| Direct liquid cooling | Cold plates remove heat directly from CPUs/GPUs. | AI and HPC racks above normal air-cooling limits. |
Singapore and tropical operation
Singapore data centres operate in a hot, humid climate, so cooling efficiency is a national infrastructure issue. IMDA's tropical data centre standard encourages operators to safely run at higher temperature settings, supported by monitoring, staged testing and equipment compatibility checks.
Raising temperatures is not a blanket instruction. Operators need to understand server inlet limits, humidity, dew point, warranty requirements, air management, failure modes and customer SLAs before changing set points.
Metrics that matter
- PUE. Total facility energy divided by IT equipment energy. Lower is better, but compare only like-for-like facilities and measurement boundaries.
- Rack inlet temperature. What the server actually sees, not only the room thermostat.
- Delta T. Temperature difference between supply and return air or water. Poor delta T often means bypass or recirculation.
- Water usage. Important where evaporative cooling or cooling towers are used.
- Thermal margin. How much headroom remains during cooling-unit failure or maintenance.
Sources and further reading
- IMDA tropical data centre standard announcement
- IMDA Green Data Centre Roadmap
- The Green Grid PUE definition