The strategic technical objective of the project is to improve the performance, durability and robustness of heat pump units, by integrating a new reciprocating or hydraulic piston type expander and optimizing its design and combined operation at a wide operation range. This concept will finally lead to performance increase, while keeping the cost of the expander low, in order for the specific operational cost and pay-back-period of this combined unit to be significantly reduced. As a result, the overall objective of the project is to open new markets for the participating SMEs, and further develop new products and services, in order to magnify their business cycle. Specific S&T objectives are:

  • Reciprocating or hydraulic piston type expander: Design and development of this key component. This expander will be developed, using also advanced numerical tools (CFD) for the investigation of the fluid flow and especially of the inlet/outlet flows from the valves/ports (of critical importance for part load operation). Then, it will be manufactured, focusing on the elimination of leakages, which can decrease its efficiency. A dedicated test-rig will be developed in the laboratory of FIR for the testing of this expander. Special focus will be given on its expansion efficiency (including the isentropic, mechanical, and volumetric efficiency) at various operating conditions, which is expected to be higher than 60% in continuous operation.
  • Integration of the expander in a re-designed commercial heat pump unit. This integration will require a slightly different design, which will be investigated during the project. Also, the control unit will be modified, in order to optimize the combined system efficiency (at partial and full load), achieving higher COP values. It should be noticed that the compressor/motor will be smaller (lower capacity and cost) than in the original design, resulting to a small increase of the unit’s cost (Milestones 4 and 5).
  • The retrofitting of an installed heat pump, using the developed expander, in order to boost its performance. The relevant know-how will be gained during the project, resulting in a retrofit kit capable to be used in a wide range of heat pumps and compressors (e.g. hermetic, open), having a significant impact at pan-European level. The additional cost introduced can be recovered in few years from the resulting lower operational energy cost of the unit.
  • Elaboration of methodologies and tools (including modeling,simulation, optimization, sizing, installation, modification and maintenance guidelines) that will enable the SMEs to adapt the products to the needs of various end-users, including the up- and down-scaling of the expander, being suitable to be integrated in various VCC (Vapour Compression Cycle) units.
  • Implementation of 3 test rigs in total, testing the expander and the two combined concepts. The first test-rig will be installed in FIR, where the research facilities will focus on the development of the reciprocating or hydraulic piston type expander. The second test-rig will be installed in KTH, integrating the expander in a re-designed heat pump and testing this combined system, while the third test-rig will be installed in NTUA, effectively retrofitting a heat pump and measuring the performance increase at both heating and cooling mode. These experimental facilities would allow the extraction of realistic conclusions, regarding the effectiveness of technical solutions, as well as the functionality of the units under real operating conditions. Monitoring will allow the measuring of the durability, performance and reliability of the main parts, the modified control units and the two combined systems as a whole.
  • Monitoring of the prototypes by the SMEs and presentation to prospective customers to validate and exploit the research results provided by the RTD performers.
  • The development and standardization of the expander and the re-designed heat pump unit and preparation of their mass production and introduction to the market, including the training of technicians of the SMEs in the installation and maintenance. Different power capacity and operational characteristics (e.g. pressure, temperature, and working medium) for the expander and the new heat pump unit will be considered, covering a wide range of the VCC units to be applied. Moreover, a proper retrofit kit will be standardized, covering a large capacity range of heat pumps.

Reduced specific energy cost and low pay-back-period for the combined operation of this expander in a heat pump unit is expected to be achieved at the project end. Focus will be given on keeping the expander cost low, in order to secure the cost-effectiveness of this concept.