Developing a 1.2 kW air-to-air single room heat pump unit for heating, ventilation and air conditioning - Acronym: Heat Pump - Deliverable 1, WP1: Scientific concept development (D1.1 Report on prototype heat pump cycle, D1.2 Report on Heat Pump system specific heat transfer properties, D1.3 Report on investigation on combined fan and motor package)

Report, 2011

This report sums up the current knowledge on basic thermodynamics, heat trans-fer etc. Combining this information and the design goals presented in the Description Of Work (DOW) has resulted in a set of target values that reflect on the design specifications. The analysis has lead to the formulation of a rating condition and a set of design goals regarding capacity and efficiency at full load and part load respectively: • Rating condition: Temperature, outdoor = +7 °C, indoor = +20 °C • Full load (100 %): Heating capacity = 3.6 kW with COP = 3.0 • Part load (50 %): Heating capacity = 1.8 kW with COP = 4.7 Design specifications on noise etc. are also included. All global target values are chosen to be competitive with current best practice, in particular at the all important part load condition (this is backed by an up-to-date market analysis). The design focus is on a rotating heat pump with liquid-ring compressor. At this, introductory stage, much of the effort has been directed to the garner information on liquid ring compressor design, fan principles and heat transfer at moving surfaces. Preliminary analysis on the required component performance to be able to reach the listed design goals above has resulted in design target values for: • compressor Carnot efficiency ( in a heating heat pump cycle), • air-flow capacities at the condenser and evaporator respectively, • heat exchanger efficiencies and heat transfer capacities, The critical design condition is part load capacity at the condenser and full capacity at the evaporator. As most of the operating hours will be at part load, given the desire to achieve reasonable energy coverage, part-load performance will be paramount. Hence a full chapter is devoted to new motor and motor-drive technology to achieve high efficiency even at low capacity turn-down ratios. This includes BLDC (BrushLess DC) as well as PMSM (Permanent Magnet Synchronous Motor) techniques. First impression from the analysis of the refrigerant side is that a hydro carbon, e.g. R290 propane, is a likely first choice. Important issues to tackle will be the compatibility between the refrigerant and the lubricating and sealing fluids.