Vapour quality sensors for energy reduction in flooded ammonia systems.

The latest research within control and regulation of flooded ammonia refrigeration system design shows great incentive to optimise the flow through evaporators (air coolers, plate freezers, and plate heat exchangers). The Danish Technological Institute carried out a number of research and development projects. These demonstrated that a vapour quality sensor and a capacity flow control system would improve the COP by 13-19 % or improve the cooling capacity by up to 16%.

The HB vapour quality sensor will make a difference in following applications:

  • Installations with height difference between the flooded evaporator and the pump separator/liquid pump. The height difference can be up to 6 m.

  • Installations with a plate heat exchanger, air coolers, and plate freezer in general. The load capacity on the plate heat exchanger influences the efficiency of plate heaters. A low circulation rate is essential for high efficiency but it requires a sensor for vapour quality and capacity control. The test result at the Danish Technological Institute shows savings in COP as well as increased cooling capacity.



The report “Elimination of wet return lines in ammonia systems” written by Anders Mønsted can be downloaded here. In the abstract of this report, fundamental figures of pressure loss as well the saving potential show:

  • 0.1 bar pressure loss in the suction line corresponds to 2°C at te = 35°C

  • 2°C improvement in the suction temperatures gives a COP improvement of approx. 8 % for a one-stage ammonia compressor


The HB vapour quality sensor for flooded system design is named HBOVC and is available from HB Products. Read more about these products at