Field test study of a novel defrosting control method for air-source heat pumps by applying tube encircled photoelectric sensors.

To improve the defrosting accuracy of air source heat pumps (ASHPs), this paper proposes a novel defrosting control method by applying tube encircled photoelectric sensors (TEPSs). A field test was conducted for two heating seasons in Beijing, China, to verify the feasibility and practicality of the novel TEPS method. The test results revealed that irrespective of the environmental conditions, the TEPS method can initiate defrosting in similar situations: most of the heat exchanger surface had been covered by frost; the compressor suction temperature decreased by ~9 °C; the compressor discharge temperature increased by ~16 °C; and the heating capacity decreased by ~30%. Furthermore, the TEPS method was verified to make more accurate and more reasonable defrosting decisions than the traditional T-T method under both frosting and non-frosting conditions. The results indicate that the TEPS method is a competitive defrosting control method that can be used for ASHPs. [ABSTRACT FROM AUTHOR]