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Heating & Cooling Coils - Heat Recovery

  • Tube Materials: Carbon Steel, 304 or 316 Stainless Steel
  • Tube Diameters: 3/8", 5/8", 7/8", 1"
  • Fin Materials: Aluminum, Epoxy Coated Aluminum, Copper, Cupronickel, Carbon Steel, Stainless Steel
  • Hot Dip Galvanized Steel Construction
  • Gasketed Removable Headers for Tube Cleaning
  • Corrosion resistant coatings


  • ASME
  • UL
  • CRN
  • PED


Heat recovery using coils offers the prospect of very attractive financial return on investment in many situations. Saving energy makes sense environmentally as well by reducing the amount of fossil fuel burned and reducing a facility's carbon footprint.

Flue Gas

Flue gas from combustion boilers contains a significant amount of heat which can be recovered and used to perform useful work such as heating water. Gross flue temperature must be determined and the appropriate materials used for tubes and fins in the heat recovery coil to a) handle maximum expected flue gas temperatures and b) provide adequate corrosion resistance. Carbon steel tubes and fins are generally limited to a maximum of 750 deg F (400 deg C) for prolonged service life of 20 years or more. Stainless steel (304 and 316) tubes and fins can be used for temperatures as high as 1700 deg F (926 deg C). It is important to control the flowrate and temperature of the heat transfer medium to prevent the surfaces of the heat recovery coil from falling below 275 deg F which is the dew point of the flue gas. If the temperature of the heat recovery coil is allowed to fall below 275 deg F and sulfur is present in the fuel then corrosive conditions on coil surfaces become a possibility. All stainless steel construction can be used to mitigate corrosive operating conditions. Colmac can provide heat recovery coils fitted with transition sections for atmospheric or pressure boilers as well as applications engineering assistance for your flue gas heat recovery opportunity.

Dryer Exhaust

Exhaust from drying equipment contains energy that can be captured and used to preheat makeup air to the dryer. Use of appropriate materials for tubes and fins (see above) and heat transfer fluid for the exhaust temperature is important to consider. A number of high temperature heat transfer fluids are available on the market to recover exhaust heat at temperatures as high as 750 deg F (400 deg C). High temperature heat transfer fluids include Syltherm, Dowtherm, Therminol, Globaltherm, Paratherm, Dynalene HT, and Duratherm.

Runaround Loop

All occupied spaces require some amount of fresh air to be introduced for health reasons. In certain types of facilities (i.e. hospital surgeries) 100% outdoor air is required. The supply of fresh air means that an equivalent volume of air must be exhausted, which can represent a significant amount of lost energy. Mounting coils in the supply and exhaust airstreams and circulating a working fluid between is an effective way of easily recovering as much as 50 to 70% of this energy. Contact your Colmac sales engineer for assistance in selecting runaround loop coils to produce the optimum energy savings and payback period. 

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