Compression converts electrical input into compressed-air output and heat. In an oil-injected screw compressor, a large part of that heat is carried by the cooling oil and then rejected through the cooler. When a factory also needs hot water or process heat, a properly engineered recovery loop can transfer part of this thermal energy to a useful load.
How compressor heat recovery works
A heat-recovery unit introduces a heat exchanger between the compressor's hot circuit and a separate water circuit. The fluids remain separated while heat passes through the exchanger. Controls regulate water temperature and protect the compressor's required operating temperature.
Where the recovered heat can be used
- Process or wash water where the required temperature and water quality are compatible with the design.
- Preheating make-up water before a boiler or another heating process.
- Space heating through a suitable hydronic circuit.
- Domestic hot-water preheating when local hygiene, storage and separation requirements are met.
- Other steady thermal loads that operate at the same time as the compressor.
What to assess before installation
- 01
Compressor load profile
Heat is available only while the compressor is operating. Review loaded hours and seasonal demand rather than using motor rating alone.
- 02
Heat-user profile
Identify when hot water or process heat is needed, the required temperature, flow and storage capacity.
- 03
Hydraulic integration
Define pumps, tanks, valves, bypasses, expansion provisions and control points for the water circuit.
- 04
Compressor protection
Maintain the operating temperature required to prevent condensation, lubricant problems or thermal alarms.
- 05
Water quality and maintenance
Select exchanger materials and a cleaning plan for the actual water chemistry and contamination risk.
Evaluate savings from site data
The economic result depends on compressor loading, recoverable temperature, simultaneous heat demand, the fuel or electricity displaced and local utility prices. A credible proposal should show these assumptions and account for pumps, storage, controls, maintenance and periods when recovered heat cannot be used.
Heat recovery works best as part of a system assessment. When the compressor load and the heat demand overlap, it can reduce the amount of purchased energy used for heating without changing the factory's core process.
