Study On Field Evaluation Method Of Direct Condensing Floor Radiant Heating System With Air Source Heat Pump

Air Source Heat Pump(ASHP,Air Source Heat Pump)is used in building,industry,agriculture and other applications on an increasing scale and area.In order to improve the air source heat pump evaluation system and enhance the system performance,the field measurement of air source heat pump system performance is necessary.The current field testing technology for air-water and air-air type systems is relatively mature,and there is a gap between the field measurement methods for direct condensing air source heat pump systems that have emerged in recent years and the research on performance testing methods for air source heat pump systems under restricted spaces.In this study,we systematically carried out the field evaluation of air source heat pump direct condensing floor heating system around the existing test methods,and proposed the outdoor air enthalpy difference method combined with CFD simulation,i.e."optimized outdoor air enthalpy difference method".A field evaluation device was developed to evaluate the performance of air source heat pump units in a restricted space,and the possibility of using this method to quantify the energy loss caused by frost,and to optimize the logic for judging frost and defrosting the units was envisioned.The main work is as follows:First,by analyzing the characteristics of direct condensing air source heat pump systems,the enthalpy difference method of air on the outside of the room and the refrigerant enthalpy difference method were used as the field performance measurement methods of air source heat pumps,and the corresponding test devices were developed.The test accuracy of both the electrically heated refrigerant enthalpy difference method and the outdoor air enthalpy difference method reached ±11.0%,and both test devices meet the test requirements and can be applied to the field performance evaluation of air source heat pump direct condensing system.Secondly,in order to reduce the workload of multi-point testing in the field,the outdoor air enthalpy difference method combined with CFD simulation,i.e.,the "optimized outdoor air enthalpy difference method",was proposed to reduce the test accuracy due to the uneven distribution of airflow organization in the restricted space.Based on this,a model of air source heat pump test platform under restricted space is constructed,and the feasibility of this method for unit performance testing under restricted space is verified through model analysis and experimental verification.Finally,the "optimized outdoor air enthalpy difference method" is applied to the field performance evaluation of air source heat pump direct condensing system under restricted space,and the accuracy of the test method is analyzed under typical frost conditions,continuous variable conditions and long-term operation conditions.The operating characteristics of the unit under dynamic frost conditions,the operating characteristics of the outdoor fan and the quantification of the frost loss of the unit were also tested and analyzed,and the feasibility of the test method for quantifying the energy loss caused by the frost of the unit was initially demonstrated.This paper presents a systematic study of the field test method for direct condensing air source heat pump system performance,and verified by enthalpy difference laboratory and field tests.The results show that the test method meets the engineering test needs in terms of test accuracy,and can provide a methodological basis for the field evaluation of different types of ASHP end systems.