Air compressor heat exchanger

By Frank Moskowitz for the Compressed Air Challenge®

Having a fundamental understanding of how your plant compressed-air system works and what forces influence it will help you improve its performance. The overall efficiency of a compressed air system can be as low as 10-15%. The figure below shows two main components of inefficiency; one is from the wasted air due to losses through Leaks, Artificial Demand and Inappropriate uses. The other is due to heat of compression. With some basic understanding, as much as 90 percent of that heat can be recovered for use in your operation.

Its simple physics that compressing air gives off heat. The heat energy is concentrated in the decreasing volume of air. To maintain proper operating temperatures, the compressor must transfer excess heat to a cooling media before the air goes out into the pipe system. As much as 90 percent of that heat can be recovered for use in your operation. If you can supplement or replace the electricity, gas or oil needed to create hot water for washrooms, or direct warm air into a workspace, warehouse, loading dock, or entryway, the savings can really add up. The possibilities to recover this waste heat via hot air or hot water are good. The return on the investment for energy recovery is usually as short as one to three years. In addition, energy recovered by means of a closed loop cooling system (for water cooled compressors) is advantageous to the compressor's operating conditions, reliability and service life due to an equal temperature level and high cooling water quality to name but a few.

This diagram illustrates some of the typical application areas for energy recovery available from the compressors cooling water in different temperature ranges. In the highest temperature levels (from oil free compressors) the degree of recovery is the greatest. The highest degree of efficiency is generally obtained from water cooled installations where the compressor discharge cooling water can be connected directly to a continuous process heating requirement. For example, the heating boilers- return circuit. Surplus energy can then be effectively utilized all year round. Most new compressors from the major suppliers can be adapted to be supplemented with standard equipment for recovery.

“Compressors are better at producing heat then compressed air” says Tom Taranto of Data Power Services.