Industrial Heat Pumps

 

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. A conventional washing machine is visualized in the figure below. The washing water is pumped through a heat exchanger and is heater by a gas fired boiler. With a spray fan the washing water is pressurized and sprayed over the product. A part of the washing water will evaporate in the air, but the main part of the water flows back to the water tank. 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.

Industrial washing machine with conventional heating

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. A washing machine with heat pump is visible in the figure below. The evaporator (cold side) of the heat pump is placed inside the air discharge duct. In the evaporator humid air is cooled down below the dew point. The temperature level of this waste heat is increased by the heat pump. In the condenser this heat is used to heat the central heating circuit of the washing machine. The boiler is used maintained, because the amount of heat in the exhaust air will not be enough to heat the complete washing machine. It is also possible to directly heat the washing water with the condenser. However, when a washing machine has more than one washing section, it is easier to heat the central heating circuit.

Industrial washing machine with heat pump

To realize a high efficiency, it is important that the discharge air has a high relative humidity. This can be realized by controlling the amount of discharge air based on the relative humidity or the pressure inside the washing machine.

The heat demand of the washing installation depends on several factors. The most important are:

  • In- en outgoing temperature of the product
  • Amount of vapor that is evaporated and discharged
  • Heat losses through surface of washing machine

Based on the size of each of these heat flows, it is possible to determine if the complete washing machine can be heated with a heat pump. Mostly an additional (existing) heat source is necessary to get enough heat.

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