Isotherm, Inc.

Heat Exchangers for Heat Pump Applications in District Heating using Natural Refrigerants

Currently the biggest issue is the control of gases that play a detrimental role in global warming. These harmful gases are generated by the power plants consuming fossil fuels.  One way to reduce the use of energy produced by these sources is to not use it.  In turn, look for renewable energy sources. In the field of refrigeration, a topic in discussion is the use of heat pumps for district heating using natural refrigerants. By definition, a heat pump is a device that transfers heat from a colder area to a hotter area using mechanical energy. In the case of heat pumps for district heating, the source of heat can be waste heat from industrial processes or natural sources like lakes or rivers, or even wastewater can be used as a source. Multiple articles and online sources are available for more details about the mechanics of heat pumps.

In 2010, Isotherm, Inc. designed and fabricated several high efficiency heat exchangers for a 14 MW District Heating facility in Drammen, Norway. The heat source is cold seawater from the Norwegian fjords, while the refrigerant for this heat pump application is ammonia. More information regarding the Drammen facility has been highlighted in an article published by the British Broadcasting Corporation (BBC); refer to the following link:

The list of the heat exchangers built are as follows:

  • Titanium Shell & Tube Low Charge Ammonia Spray Chiller (Cooling seawater to 39.2 F with only 3.6 F approach)
  • Shell & Tube Stainless Steel Enhanced Tube Subcooler
  • Shell & Tube Stainless Steel Enhanced Tube Intercooler
  • Shell & Tube Stainless Steel Enhanced Tube Desuperheater
  • Shell & Tube Stainless Steel Enhanced Tube Condenser

While ammonia has been used as the refrigerant for these heat pump applications, there has been an increased emphasis on the use of CO2 as the refrigerant. In 2019, Isotherm built the following heat exchangers that went to a Hydroelectric facility in the Canadian province of Quebec:

  • Shell & Tube Flooded CO2 Evaporator
  • 3 stacker CO2 Gas Cooler

Thus, Isotherm’s design of heat exchangers for heat pump applications is not new and is striving to further its technology for this application in order to contribute the goal of reducing the carbon footprint.