Advanced Frost Sensor for HVAC Applications

Frost is a common problem in heating, ventilation, and air conditioning (HVAC) systems that can degrade their efficiencies, leading to excessive electricity consumption. Appropriate defrosting is therefore essential for heat pumps and refrigeration systems. However, these systems typically run the defrost cycle based on a predetermined time interval, a method that does not accurately identify the amount of frost and thus consume excessive electricity. This paper describes development of a smart sensor that can substantially improve defrosting initiation and termination and is based on a capacitive sensing technique that can quantify frost accumulation and distinguish the difference between frost, ice, and water. The reported sensor employs interdigitated comb electrodes and can be updated to a potential multifunctional sensor array for enhanced identification of frost, ice, and water via the integrated measurement of surface temperature, frost capacitance, and resistance. The proposed frost sensor is expected to have widespread applications in HVAC systems, including heat pumps, refrigerators, and commercial refrigeration systems.