Acoustic comfort improvement of simultaneous heating and cooling heat pumps using control logic for flow-induced noise reduction

Abstract

Acoustic comfort in buildings can be achieved by minimizing unwanted noise generated primarily from heating, ventilation, and air-conditioning systems. However, research on noise reduction in simultaneous heating and cooling heat pumps (SHCHP) is limited. This study proposes a novel noise reduction control logic (NRCL) based on experiments on flow-induced noise through electronic expansion valves (EEVs) in an SHCHP. The flow-induced noise through EEVs was measured and analyzed regarding the degree of subcooling, differential pressure between indoor unit and evaporation (ΔPindoor), EEV opening speed (Vo), and opening (Oeev) while switching operation mode in an SHCHP. For all the operating and controllable variables, the peak sound pressure level (SPLpeak) was decreased by evenly distributing sound energy (SE). The sensitivity analysis indicated that Oeev and Vo were the most significant variables for achieving uniformly distributed SE. Therefore, a novel NRCL was proposed in terms of the initial EEV opening (Oeev,i) and dimensionless control time (CT) derived from the relationship between Oeev and Vo. The optimal CT for EEVs in SHCHP with NRCL was 1. At this point, the difference between SPLpeak and average SPL decreased by 46.2%, and the converging time for ΔPindoor to 0 increased by 17.8% compared with those of baseline.