Study On The Impacts Of Outdoor Heat Exchanger Fouling On The Operating Performance And The Fouling Fault Diagnosis For Ashp

Air source heat pump(ASHP)has been widely accepted in many parts of the world,and classified as one of renewable energy sources technologies in China.However,when ASHP operates in the dusty environment,fouling can be quickly formed on its outdoor coil surface,impacting negatively on the ASHP performance.To effectively alleviate the negative impacts of fouling,a study on the impacts of fouling on operating performance and the fouling fault diagnosis for ASHP was reported.Firstly,a field study on the fouling formation process was conducted,and the main objective factors of fouling formation were analyzed.Secondly,the cooling and heating operating performance degradation of ASHP units with fouling fault were revealed.Thirdly,the cooling and operating performances of ASHP under different degrees of fouling were presented.The main influencing factors that affect the performance degradation of ASHP were analyzed.Finally,the reasonable defouling point was analyzed,and the characteristic parameter of TTT(ambient temperature-condensation temperature-outlet air temperature)was proposed which can reflect the degrees of fouling.The TTT fouling fault diagnosis method was was developed.The applicability and efficiency of the TTT method was verified during cooling seasons.Research results indicate:(1)Fouling was inevitably formed on the outdoor coil surface of ASHP in the actual operation.The outdoor coil located in vegetation and plant environments,the dust particles in ambient air and the long operating of ASHP were caused by the frequent occurrence of fouling fault.(2)Fouling fault changed the operating parameters by 11%~147%,reduced COP by 18%~28%,and even lead to the shutdown of ASHP,which was 2.5 times per hour in high ambient temperature cases,resulting in huge energy consumption for ASHP.Furthermore,fouling fault was not reasonable to exclude,resulting in the heating performance deterioration of ASHP.(3)Most of operating and cooling parameters of ASHP were affected by both the degrees of the fouling and the ambient temperature.The operating and cooling parameters of ASHP with different degrees of fouling were changed by 1%~121% and 1%~29%,respectively.(4)The TTT fouling fault diagnosis method can effectively detect fouling fault in a cooling seasons,the average COP was increased by 11% compared with the unused method during a cooling season.In summary,fouling formation for ASHP is inevitable,resulting in significantly negative impacts on the ASHP performance.The TTT method can effectively alleviate the fouling fault to improve the ASHP performance.