Potentials of implementing liquid-separation to a transient wrap-around microchannel condenser coil within heat pump water heater

Abstract

Dynamic characteristics of wrap-around microchannel condenser coil are essential to heat pump water heater (HPWH) during heating-up transient. In this paper, effectiveness of applying liquid-separation technology to the wrap-around microchannel condenser coil is discovered. A mathematical model adopting “quasi-steady-state” and “segment-tube-path” approaches is established for the water tank and microchannel condenser coil. Its predictions on both liquid-separation microchannel condenser coil (LMC) and conventional microchannel condenser coil (CMC) are in good agreements with experimental data. Results show that simply employing separators in the condenser coil (LMC-I) does not bring improvement. The average heat transfer coefficient of LMC-I is enhanced by 10.34% and 5.75% at the entrances of the second and third paths compared to that of CMC, respectively, whereas it is degraded at the outlets of the second and third paths as well as in the entire fourth path. However, LMC-I achieves a significant pressure drop reduction by 34.48%. Thereafter, LMC-II is screened from 963 candidates of path arrangements, and has better performances in terms of higher heat capacity and shorter heating time than both CMC and LMC-I. Its average proportion of 51.83% of two-phase area to the total area is also superior to both CMC and LMC-I.