Heat Pumps

Industrial Heat Pumps

Heat pumps are widely known for their heating and cooling applications in the residential sector, but they are still under-deployed in industrial applications. In fact, many industries can economically benefit from the installation of this technology. Heat pumps provide heating and cooling, using waste energy from processes. Increasing the energy efficiency of an industrial process, by installing a heat pump, will result both in cost reductions for the industry and in positive environmental impacts for the whole society. Today, heat pumps are used in a wide variety of applications especially in sectors like food & beverage, tobacco, wood & paper or chemical, pushing further and further the research of more performant solutions.

Industrial heat pumps are defined as equipment to actively recover waste heat. The system is rather simple: heat pumps increase the temperature of a waste-heat streams to a higher temperature, making those steams usable again. Particularly efficient when direct heat exchange is not possible, the heat pump technology can find application in several industrial processes, going even beyond a closed circuit and allowing the creation of integrated system with different processes or users. Recovering waste heat flow from: waste water, hot humid air, condenser heat from refrigeration systems, etc., heat pumps can then power process like: high temperature heating, blanchers, dryers, refrigerator, cleaning, central heating & cooling systems and even district heating.

 

Waste heat sources that can be valorized with heat pumps

  • Waste water
  • Humid off gases from drying processes
  • Water streams that need to be cooled before further treatment
  • Waste heat from chillers (refrigeration)
  • Processes that require cooling

 

Typical processes 

  • Drying and dehydration
  • Evaporation
  • Washing, cleaning
  • Cooking
  • Sterilization, pasteurisation
  • Space heating
  • District heating
  • Industrial plants provide a wide variety of heat sources and potential users; thus, numerous other applications can be guaranteed by heat pump technology. In particular the heat recovered from all above-mentioned process can be also use to power process other than the original one, especially heating systems.

 

How does a heat pump work? 

Heat pumps convert low-temperature heat into higher-temperature heat, even in winter when it is well below freezing. This process takes place in a closed circuit and involves constantly changing the state of the working fluid (evaporation, compression, condensation, expansion). Refrigerators operate on the same principle to extract heat from inside and discharge it to the outside. By contrast, heat pumps take stored solar heat from the environment around the house - soil, water or air - and release it together with the input energy in the form of usable heat to the heating and hot water circuit. The heat pump operates on the basis of a working fluid (coolant) which changes state (liquid/gas) in a continuous cycle and absorbs and releases heat.

The heat pump cycle is essentially based on the Carnot cycle. Its steps are: 

  1. Evaporation
    In a heat exchanger, the liquid refrigerant absorbs energy from the heat source (water, soil or air) and evaporates as the temperature rises.

     
  2. Compression
    In a compressor, the introduction of electrical energy causes the vaporized but still cold coolant to compress and heat up. The coolant leaves the compressor as a hot gas.

     
  3. Liquefaction/condensation
    The hot gas flows into the liquefier, releases energy to the heating system, condenses and leaves the condenser as hot, liquid refrigerant. This energy heats the hot water for heating or domestic use to the desired temperature.

     
  4. Expansion
    The hot, liquid refrigerant is transferred to the expansion valve. In the expansion valve, the pressure is reduced very rapidly. The temperature of the coolant also drops very quickly without releasing energy. The cold, liquid refrigerant is transferred to the evaporator and the cycle begins again.

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