Open loop

Open loop heat pump system in DryFiciency 

Three novel heat pump demonstrators will be elaborated in the project. Each of the demonstrators will be designed, constructed and commissioned at the respective industrial site and operated under real industrial conditions.

This page describes the open loop demonstrator. Sketch of DryFiciency open loop heat pump system

The concept of the open loop heat pump is also knows as Mechanical Vapour Recompression or MVR. These heat pumps use water (R718) as a refrigerant in steam drying processes where goods are dried in a steam atmosphere. In these processes, steam is circulated and reheated by a natural gas burner with water removed from the product in the form of excess steam. Usually, this excess steam cannot be used further because there is no heat demand at this temperature and it is therefore wasted. In this case, the excess steam of the dryer can be compressed directly by the heat pump without the implementation of an evaporator. Open loop heat pumps allow for recovery of the excess steam since it is used as thermal energy source - the dryer is the evaporator of the heat pump. The compressor increases the pressure level of the excess steam, so that is can be condensed at higher temperatures. DryFiciency open loop heat pump will use turbo-compressors with a combined pressure ratio of 6 when compressing over two stages and will reach a condensation temperature of 160°C. In the condenser, the hot excess steam reheats the process steam of the dryer. Thereby, the natural gas burner can be replaced. 

Read more on this system here.  

The demonstration unit utilizes up to 1 ton of steam per hour which will result in a capacity of 750 kW. The turbo-compressors are oil-free and do not need lubrication. The successful demo case aims to reduce the energy demand of the dryer by up to 75% and to eliminate the need of the drying system to depend on fossil fuels. Water is environmentally-safe, non-toxic, reliable and natural refrigerant with no global warming potential and will not be subject to future regulations. 



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