Experimental Study on Drying Characteristics of Alfalfa Hay Bales Using Hot Air Convection

Alfalfa hay bale drying technology can effectively reduce alfalfa leaf loss and improve forage quality. However, due to the large volume and high density of fresh-stored hay bales, deep-level drying is uneven, leading to nutrient loss in alfalfa. To address these issues, a hay bale drying test bench was constructed to systematically investigate the effects of initial moisture content, bale density, drying temperature, and air velocity on drying performance. The results showed that when the hot air temperature was 70 °C and the air velocity was 2 m/s, the average moisture content of hay bales with an initial moisture content of 25% (w.b.) could be reduced to 17% (w.b.) within 1.5 h, with a drying efficiency of 26.67 kg/h. However, increasing the bale density from 127.95 kg/m3 to 144.15 kg/m3 prolongs the drying time by 50% (w.b.). Batch drying of multiple bales further reduces drying efficiency due to increased airflow resistance. The problem of uneven drying is significant, especially when hot air is introduced in the horizontal direction. Therefore, the precise control of drying parameters such as temperature, airflow direction, and bale density is essential for achieving uniform moisture reduction. These findings provide important theoretical support for the efficient drying of alfalfa hay bales.