Performance analysis of a heat pump dryer with separate heat recovery using an energy, exergy, and economic methodology

Heat pump drying system is prospect technology with high efficiency and energy saving. Stable and efficient operation of heat pump drying systems in cold climate regions is achieved using a separate heat recovery room, which is designed to recover the heat in the exhaust air. Using a separate heat recovery room aims to maintain stable operation through switching between enclosed and partial air-loop modes. This paper analyzes the drying parameters to verify the stability of system, compares the running modes, and evaluate the economy of the dryer. It is found that setting a separate heat recovery room can achieve a higher material uniformity, and the air parameters are less affected by surroundings. Moreover, modes need to be adjusted according to the drying parameters and surroundings. Meanwhile, the proposed system has a great advantage in reducing the exergy loss of the heat exchanger, which can reduce operating costs.