The demand for dried products is presently increasing worldwide due to the convenience of their storage, transportation and availability. However, the quality of dried products is lower than fresh ones and is usually dependent on the drying process. Therefore, it is essential to improve the drying methods for achieving high quality and economical products.
Traditional industrial drying equipment requires fossil fuels to produce heat, leading to increased prices of electricity and harmful airborne gases. Hence, there is a need to develop energy efficient and low carbon emission drying equipment for processing and drying biological materials.
A heat pump dehydrator transfers the thermal energy of air or water to the drying material, which reduces energy consumption and operating costs. It also helps to conserve energy and reduce environmental degradation.
Heat pump drying technology has been used for several applications, including food and biomaterials. It can be combined with conventional drying techniques such as convective and intermittent irradiation dryers (Zbicinski et al., 1992).
Moreover, radio frequency energy can be used to enhance the heating effect in a heat pump batch dryer for faster initial drying rate and improved product quality (Marshall and Metaxas, 1999). The combination of IR drying with convective air drying resulted in a significant improvement of the quality of garlic and white mulberry leaves (Phoungchandang, 2009).
The performance of heat pump drying systems is characterized by the amount of energy consumed by the vapor compression system, the energy efficiency ratio COP and the specific moisture extraction rate SMER. The former reflects the drying capacity of the device, while the latter indicates the ability to dry materials with a specified quality and quantity. heat pump dehydrator