This work details the experimental characterization of a Variable Refrigerant Flow Heat Pump (VRF-HP), which operates using a 3-phase compressor with a variable frequency drive (VFD). The VRF-HP is a novel and useful addition to Solar-Assisted-Heat-Pump (SAHP) systems, which use a Heat Pump (HP) to transfer solar energy into Domestic-Hot-Water (DHW).
A modified factorial experiment was conducted on a custom-built experimental test unit instrumented to measure flow rate, electrical power consumption, and outlet temperatures. Independent variables studied included mass flowrate on the source and load side of the HP, inlet temperatures on the source and load sides of the HP, and the commanded compressor speed (implemented through the VFD).
The result of this work is a set of three multivariate polynomial response hypersurfaces that describe the VRFHP's
electrical power consumption, source, and load-side heat transfer rates. These hypersurface fits can be used to model the performance of the VRF-HP on average within 5% for power consumption, 15% for source-side heat transfer, and 13% for the load-side heat transfer rates. Although these uncertainties are significant, they are small enough to permit the implementation of the model in a predictive controller or for preliminary simulation studies, provided that the models are validated over the range of conditions being simulated.Video presentation