Design and fabrication of a heat pump flatbed dryer for paddy drying

Abstract Paddy drying is a crucial step in rice production as it greatly affects the quality and yield of rice. One of the largest rice producing countries, the Philippines, is facing issues in paddy drying especially during rainy seasons. This has been a challenge to the agricultural sector as it causes significant losses to both farmers and the economy. In response, a heat pump flatbed dryer (HPFD) was designed utilizing a recycled air conditioning unit. The drying chamber of the HPFD was fabricated using stainless steel sheets and fiberglass insulation. The chamber’s dimensions were designed to accommodate 10 kg of rice upon taking into consideration the maximum amount of paddy that can be dried and the varying ambient conditions in the country. The airflow characteristics inside the drying chamber was evaluated using ANSYS. Several drying experiments were undertaken at different loads of paddy with approximately 25% of initial moisture content and an air intake velocity of 10 m/s. The moisture content reduction and drying efficiency were recorded accordingly to evaluate the performance of the designed HPFD. Results have shown that the dryer can achieve a drying rate of up to 4.25% per hour reduction in moisture content (MC), with a maximum drying efficiency of 70.87%. The findings displayed that the dryer has a comparable performance to the existing mechanical dryers currently available in the market.