Recent developments in heat pump dryers focusing on methods of supplying and reducing their energy consumption

This review aims to analyze recent advancements in heat pump dryers (HPDs) with a focus on improving energy efficiency and conservation in drying processes. The objective is to evaluate the components, structures, and refrigerants used in HPDs, examining their environmental impacts and system performance. The methodology includes a comprehensive comparison of various assisted HPD systems, such as infrared-, ultrasound-, and solar-assisted technologies, to assess their experimental benefits and limitations. By using key performance metrics, the paper evaluates the energy efficiencies of HPDs in comparison with traditional drying methods, discussing their applications across different industries. The study also explores the significance of integrating alternative energy sources to enhance the efficiency and economic viability of HPDs. Future research directions are proposed to further develop the technology for commercial use, emphasizing HPDs’ potential to provide energy-efficient and high-quality drying solutions. In quantitative terms, the review notes that the coefficient of performance (COP) for HPDs ranges between 3.5 and 4.5, indicating a significant improvement over traditional drying methods. Specific moisture extraction rate (SMER) values for HPDs are reported to be between 0.8 and 1.2 kg kW⁻¹ h⁻¹, demonstrating superior efficiency in moisture removal. Additionally, specific energy consumption (SEC) for HPDs is found to be 0.5–0.7 kW h kg⁻¹ of evaporated moisture, which is substantially lower compared to conventional dryers. These metrics underscore the energy-saving potential and enhanced performance of HPD technology.