Pulse-Width-Modulation Control of a Heat Pump Dryer with Cascade Evaporators and Parallel-Flow Condensers

Heat pump drying systems require a method to change the inflow air temperature of the drying chamber. Pulse-widthmodulation (PWM) technique with duty cycle provides a measure of controlling the voltage supplied to the electric motors. Therefore, we conducted this research to PWM control a heat pump dryer to change the air circuit parameters. In the Parallel-Flow condensers, inlet and outlet temperatures, and relative humidity, data were collected, and the average temperature values were recorded. The duty cycle was changed by developing a program using the Python programming language. An Excel-based psychrometric calculator was developed to analyze the collected data. The average condenser outlet temperatures were 56.6±0.1℃, 54.9±0.1℃, and 52.6±0.1℃, and the average condenser inlet temperatures were 43.2±0.0℃, 42.8±0.1℃, and 41.2±0.1℃ for 60%, 80%, and 100% duty cycles, respectively. The power consumption rate of the condenser reduced with an increasing duty cycle. The results concluded that the PWM control system is a viable method to control the inflow air temperature to the drying chamber.