ICR-R290 heat pump testing lead future energy efficient houses

ICR-R290 heat pump testing lead future energy efficient houses

On the fourth day of the International Congress of Refrigeration (ICR) Per Henrik Pedersen from the Danish Technological Institute (DTI) presented a study on the development and testing of small heat pumps using R290. The research demonstrated the feasibility of using R290 with a limited charge, which in the future could be used in new energy efficient houses.

Increasing environmental concerns are dramatically changing the way buildings are being designed and constructed. As more stringent building regulations are implemented low energy residential houses with a well-insulated building envelope and low energy technologies will become the norm. Given this context, small heat pumps using natural refrigerants present an attractive solution for compliance with directives on energy consumption.

Mini heat Pumps for highly insulated houses, Pedersen P. H., Jacobsen E., Madsen C., Frandsen J. Danish Technological Institute and Nilan A/S, Denmark

The objective of the project presented was to develop and test prototypes of small heat pumps for future low energy residential houses and research the possibility of using R290 with a refrigerant charge below 150g.

The heat pump was based on a variable speed compressor design originally developed for plug-in supermarket cabinets in 2006. Whilst the original design had compressor displacements of 15cm3 for R290, with the possibility to vary the speed from 2000 to 4000 rpm, for the heat pump prototype the displacement was 12cm3.

Heat pump prototypes

The first heat pump prototype was made up of the following components:

  • Compressor: Danfoss SLV12 CNX with variable speed
  • Condenser/Evaporator: Model B3-020-24-3.0-H, Danfoss Plate Heat Exchanger, Qinbao, China
  • Expansion valve: Danfoss thermostatic expansion valve type TUBE
  • Pumps: Grundfos UPM pumps with variable speed
  • Piping: 14 inch and 3/8 inch copper piping
  • Internal heat exchanger: Danfoss HE7

The second heat pump prototype was built using Gea BP18 WP-418M-10LGX plate heat exchangers, which are slightly smaller.

Prototype laboratory testing

Testing of the protoype heat pumps was done in accordance with DS/CEN/TS 14825 and DS/EN 14511. Tests were carried out with charges of 150g and 180g.

For the DS/CEN/TS 14825 test for the first prototype, bubbles were recorded in the sight glass after the condenser when the compressor was running at 2000 and 3000 rpm. To correct this additional charge was added up to 180g. The capacities and coefficient of performance (COP) values were as follows:

  • At 2000 rpm: COP of 3.44 – 3.63, capacity of around 1000 – 1100 Watts
  • At 3000 rpm: COP 3.3 – 3.48, capacity of around 1500 – 1600 Watts
  • At 4000 rpm: COP 3.19 – 3.2, capacity of around 2100 Watts

For the DS/EN 14511 test the first heat pump was tested in 3 running conditions, with a charge of 150g. The capacities and COP values were as follows:

  • At 4000 rpm: COP of 3.19, capacity of around 1000 Watts
  • At 3000 rpm: COP of 3.34, capacity of around 1500 Watts
  • At 2000 rpm: COP of 3.16, capacity of around 2000 Watts

The second prototype the COP appeared to be slightly less efficient then the first, thought to be due to the smaller heat transfer area.

Overall, the heating capacity of the prototypes was measured to be between 1 and 2.1 kW and the COP measured to be between 3.2 and 3.6, depending on the compressor speed and type of plate heat exchanger used.

Testing of a similar small heat pump using a fluorinated refrigerant in a highly insulated EnergyFlexHouse in Denmark has shown that small heat pumps are a viable solution for low energy houses.

happy wheels
Share this