Study On The Influence Of The Change Of Dry - Wet Blower Temperature On The Performance Of Duct - Type Heat Pump

Performance test of air conditioning units must be carried out under the experimental condition specified in the national standard. Measurement accuracy of the surrounding dry and wet bulb temperatures is of great importance to test results.To ensure the reliability of the performance test results, national standard (GB/T. 7725-2004 Unitary Air Conditioner,2004) strictly defines the dry-bulb and wet-bulb temperatures (D&WBTs) variations as±1℃ and ±0.5℃, respectively. However, with the increasingly requirements of energy efficiency for air conditioners, necessity of stricter settings of D&WBTs variations and effects of D&WBTs variations on performance of air conditioning unit and energy efficiency grade are in urgent need of further study. In this paper, theoretical and experimental research on performance of ducted heat pump in cooling and heating conditions are carried out when D&WBTs change in the variations set in national standard in China.Experiments on performance of ducted heat pump when indoor and outdoor D&WBTs separately and coupling changed within variations set in national standard were conducted by means of air-enthalpy method in a psychrometric chamber, respectively.Curves of refrigerating capacity, EER, heating capacity and COP changing with the rising DBT or WBT are drawn. Three-dimensional scatter distribution of refrigerating capacity, EER, heating capacity and COP changing with the rising DBT or WBT are mapped. The influence degree and deep-rooted reasons of four factors namely indoor D&WBTs and outdoor D&WBTs on unit performance in cooling and heating condition are discussedThe deviations between test results in the standard working condition and that of the most favorable and unfavorable working condition for the prototype within the tolerance of national standard are worked out. The indoor WBT was found out to be the most significant factor with influence coefficient of 0.0464 on EER in cooling condition, while the indoor DBT was found out to be the most significant factor with influence coefficient of-0.0582 on COP in heating condition.A new concept of variation grade is provided to judge the energy efficiency class of air conditioner unit more accurately. Strictly DBT ±0.3℃ and WBT±0.1℃ is provided, and the measurement error of EER drops from ±3.5% to ±1%.The variation correction calculation software is developed to reduce the effects of variations on unit performance.