Feasibility and optimization of defrosting control method with differential pressure sensor for air source heat pump systems

Highlights: • A novel defrosting control method using differential pressure sensor is proposed. • Optimum sensor location is set with preliminary experiments and CFD simulations. • A strategy to deal with several operating conditions and specifications is developed. • The suggested method is experimentally verified under various frosting conditions. -- Abstract: A defrosting control method with differential pressure sensor is suggested in this study for air source heat pump systems. To maintain the performance of the heat pump system under frosting conditions, it is crucial to determine the start time of the defrosting process properly. Thus, this study investigates the feasibility of using the differential pressure sensors for defrosting control and further optimizes the control method. Firstly, the optimum location of the differential pressure sensor for air flow is determined by preliminary experiments. Secondly, a method to deal with various changes in operating conditions and system specification is developed. Lastly, main experiments are conducted under various frosting conditions to validate the suggested control method using differential pressure sensors. To show the reliability of the control method under various frosting conditions, two different error factors are defined; error on a time basis and a capacity basis. As a result, the root mean square of the error for the defrosting time is 6.4% on a time basis and 5.1% on a capacity basis.