Industrial Heat Pumps



Heat pump installation ready to go on transport When is it profitable to apply a heat pump?

Heat Pumps can be used in several industrial processes. Industrial plants have both waste heat flows and heat consumers. Waste heat flows are for example: waste water, hot humid air, condenser heat from refrigeration systems, etc. Heat consumers are process water, central heating systems, blanchers, dryers, etc.

In complex industrial applications, a pinch analysis may be performed to assess the suitability of waste heat integration. For processes that are less complex, the method described below will help in forming a decision.

1. Identification

Identify all heat consuming processes. For waste heat sources as well as potential waste heat consumers the following information must be collected:

  • Medium
  • Temperature
  • Power

2. Direct heat exchange

For waste heat flows with higher temperatures than their potential users, direct heat exchange is possible. In this situation a heat pump is not needed to transfer the heat.

3. Using a heat pump

Waste heat flows with a temperature level lower than the heat consumers do not offer a possibility for direct heat exchange. It may then be an interesting option to upgrade the temperature level using heat pumps. The efficiency of the system will depend on the temperature levels, power and hours of operation. You may use our feasibility check to determine the feasibility of using a heat pump.

Typical applications

Drying processes
Drying is an important industrial process. Various temperature levels and drying principles are applied in industrial dryers. The most common dryer type is one in which air is heated with steam, gas or hot water and then circulated over the wet product. As the air picks up moisture from the wet product, its humidity increases and the energy contained in this stream may make it a useful heat source. Standard procedure is to exhaust this humid air or dehumidify it. With a heat pump, heat can be extracted from the humid air. The air is cooled down and dehumidified. The extracted heat can be increased in temperature and can be used to heat the dryer.

Thus, the use of a heat pump serves two purposes - heat the dryer and dehumidify and recirculate air. Heat pump assisted drying can give high efficiencies because of this. This innovative heat pump application has been realised in practice; the heat pump for drying of fries.

Read more about drying processes.

Washing processes
In industry a lot of washing processes occur. Mostly this are processes where hot water, sometimes mixed with a solvent, is prayed over a product. The washing installation is often equipped with an air discharge fan to prevent the installation from vapor flowing out through the in- and outlet opening and other openings in the washing machine. The air discharge will blow humid hot air to the ambient and will maintain an under pressure inside the washing machine. The discharge air contains a large amount of energy. With a heat pump it is possible to use the heat prom the discharge air to heat the washing water.

Heating of process water with waste heat from a refrigeration system
Typically the food industry produces products that need to be cooled or frozen before transport and/or consumption/utilisation. On the other hand, hot water is needed for the process and for cleaning purposes. Waste heat from a refrigeration system has a temperature of 25 to 30 °C. With the use of an add-on heat pump, waste heat from the condensing side of the refrigeration system is used to heat water to temperatures up to 80 °C. The add-on heat pump will further increase the pressure of the refrigerant from the refrigeration system to achieve high condensation temperatures.
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Heat pumps in practice

For pasteurization a product needs to be heated above 70 °C. Afterwards the product is cooled down. The product temperature thus varies from cold before pasteurization to hot during pasteurization and back to cold again after pasteurization. In most pasteurization processes heat exchange between the cold and hot product flow is already implemented. The cold product before pasteurization is used to pre-cool the product directly after pasteurization, or looking at it the other way around: the hot product is used to pre-heat the cold product. In addition to this extra heating and cooling are needed for pasteurization. This is normally provided by, for example, steam injection and a flow of chilled water. A heat pump might be the ideal solution to extract heat from the product that needs to be cooled and supply this heat at a higher temperature to the product that needs to reach pasteurization temperature.
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Other applications
Industrial plants provide a wide variety of heat sources and potential users. The heat pump is a promising technique with numerous applications in the industry. To investigate its feasibilty for your particular situation a pinch analysis can be performed as well as a feasibility check.

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