Experimental study on the performance of a two-stage heat pump drying system coupled with rotary dehumidification and total heat recovery

This study proposes a two-stage heat pump drying system integrated with rotary dehumidification and total heat recovery to address high energy consumption and insufficient deep dehumidification of conventional dryers. A corresponding experimental platform is established, and the single-factor experiments were conducted to explore the effects of key parameters including throttle valve opening, throttle opening of bypass vapor jet, compressor speed and drying temperature on system performance are systematically investigated. The experimental results indicate that the key parameters exert significant regulatory effects on the system coefficient of performance (COP), system COP (COPs), and specific moisture extraction rate (SMER). As the throttle valve opening and throttle opening of bypass vapor jet increase from 50% to 100% and 60% to 100%, respectively, all performance indicators present a trend of first increasing and then decreasing. The optimal performance is obtained at the opening of 80% and 70%, corresponding to COP, COPs, and SMER values of 5.49, 2.89, 1.44 kg/kWh and 5.34, 2.71, 1.68 kg/kWh, respectively. When the low/high-pressure compressor speed combination increases from 1000/1500 r/min to 1800/2700 r/min, the three parameters increase by 16.6%, 20.98%, and 33.3%, respectively. Under all experimental conditions, the dehumidification proportion of the rotary dehumidification ranges from 74.57% to 82.88%, and the total heat recovery efficiency varies between 22% and 30%, proving the effective complementary effect between rotary dehumidifier and heat recovery unit.