Implementation and performance evaluation of a pilot‐scaled oscillating heat pipe on rice paddy drying

AbstractThailand is the foremost global producer of rice, benefiting from its hot and humid climate which results in harvested rice with a high moisture content. This promotes the rapid growth of microorganisms that harm the paddy. Consequently, the utilization of drying techniques is necessary to uphold the quality of the product. For the sake of efficiency and dependability, forced draft convection drying is commonly utilized, despite its high energy consumption. In general, the paddy is subjected to the flow of hot air, which exits the drier at a reduced temperature, leading to energy dissipation. Heat pipes have been widely employed to reclaim wasted energy through the preheating of fresh air, owing to their straightforward design and lack of reliance on external power sources. Nevertheless, there has been a scarcity of research conducted on the utilization of the oscillating heat pipe in these particular applications. Thus, a pilot‐scale oscillating heat pipe is utilized in this study. The primary aim of this study is to evaluate the efficiency of waste heat recovery using the recently developed oscillating heat pipe, as well as the resulting energy conservation. Various thicknesses of rice paddy layers are examined to compare the duration it takes for them to dry. It is seen that the drying time increases as the bulk of the paddy increases. When the layer thickness is increased, a multimodal drying rate behavior is observed which is due to the fact that when the heated air ascends, it repeatedly heats each layer of the grain. The study focuses on analyzing the temperature profiles at the heat pipe and within the evacuated air. The rate of heat recovery is also computed. An investigation is conducted to determine the energy savings achieved through the use of heat pipes. The results indicate a decrease in energy consumption ranging from 39.4% to 63.7%. This study showcases the utilization of a research‐scaled oscillating heat pipe in the rice drying procedure, serving as a foundation for the future enhancement of the heat recovery system in industrial rice drying.Practical applicationsThailand is the world's top rice producers and because it is hot and humid, the harvested rice has a high moisture content, which encourages the growth of bacteria. In most cases, forced draft convection drying is used, which uses a large amount of energy. In general, this is due to energy loss in the exhaust. Heat pipes have been widely employed to recover wasted energy. However, research on the utilization of oscillating heat pipes in such applications has been limited. Hence, a pilot‐scale oscillating heat pipe is used in this work to evaluate the efficacy of waste heat recovery as well as the energy savings. The drying time is shown to increase with the thickness of the paddy layer. The temperature profiles at the heat pipe and in the evacuated air, as well as the heat recovery rate, are investigated. The results show an energy reduction of 41.7%–53.9%.