Experimental Study On Nonfrosting Air Source Heatpump System

This paper was based on the frost mechanism of air source heat pump (ASHP), starting from destroying the two essential conditions for frosting, the Nonfrosting Air Source Heat Pump System (NASHP System) was proposed, which is a new system. Correspondent operational mode was proposed, and a test bed was built as well. By experimental verification, this new system was proved practical, and energy-saving effect is remarkable.The defrosting mechanism was studied in this paper, found that changing the dew point of outdoor air to make it below the fin surface temperature, or making sure that condensed water remain liquid state when the temperature below 0℃, either of the two can prevent frosting as well as removing the frost. Based on this, the Nonfrosting Air Source Heat Pump System was proposed, i.e. installing spray devices on outdoor heat exchangers and spraying mist flow of antifreezing liquid to the fins when necessary. Mechanism of Heat and moisture transfer was studied, modes of continues spray and intermittent spray were put forward. The regeneration mode was drew up that the solution is collected in Winter and regenerated in Summer. Glycerite was chosen in the system.The Nonfrosting ASHP Experiment Rig was designed and built, which can simulate different outdoor temperature and related humidity, carry out ASHP Reverse defrosting and solution spray defrosting, and Automatic exquisite the experimental data. Through calculation, the relative error of COP is 8.9%,. If take no account of the error of indoor air flow rate, the error of the difference between COP's is 2.2%.Continues spray and intermittent spray defrosting experiments were accomplished in different outdoor environment, and they were compared with reverse cycle defrosting. experimental evidence proved that the Continues spray mode is able to prevent frost and intermittent spray mode able to defrost. Index of machine performance, thermal comfort and efficiency for the three modes were compared. When comparing the COP between them, intermittent spray mode is the best, reverse cycle second and Continues spray the worst. When comparing the thermal comfort index and economical efficiency both, intermittent spray mode is the best, Continues spray second and reverse cycle the worst.Optimal operation time control method for continues spray mode was sought, and aθcriterion was posed. Feasible concentration of the solution was confirmed as 35~65%, and flow rate 0.53~0.64 t/(h·m2).In conclusion, Nonfrosting ASHP system has strong feasibility; the advantage is distinct, compared to hot gas defrosting. Optimization suggestions were raised at the end of this paper.