Kosasih Engkos Achmad, Zikri Ahmad, Dzaky Muhammad Irfan
Department of Mechanical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok 16424, West Java, Indonesia.
Heliyon. 2022 Jun 21;8(6):e09757. doi: 10.1016/j.heliyon.2022.e09757. eCollection 2022 Jun.
The drying method requires an effort to store food for a longer time. Some drying processes experience technical and economic weaknesses, mainly related to low efficiency, high energy costs, and decreased product quality. Various drying models have been studied to determine the suitability of heat and mass transfer analysis at drying rates in an air dehumidification scheme using different materials, one of which is silica gel. In this case, the researchers examined the effects of humidity, temperature, and airflow rate on the constant drying rate and activation energy of water desorption in silica gel using a packed bed dryer that was modified with a refrigeration system. This modified system aims to reduce specific energy consumption (SEC). The results demonstrate that the constant rate of water desorption in silica gel and the increase in air humidity cause a decrease in the constant value of the water desorption rate in silica gel. However, increases in the temperature and airflow cause an increase in the value of the constant drying rate for water desorption in silica gel, as they cause capillary evaporation. Meanwhile, the activation energy of water desorption in silica gel increases with decreasing air flow rate and increasing inlet air humidity. The attractive force acting on the water molecules from the surface force field on the surrounding walls becomes stronger if the air flow rate decreases or the air humidity increases. From the results and analysis, it is shown that the activation energy of water desorption in silica gel with significant air humidity and low flow rate, of 0.013 kg/kg d.a. (450 lpm), is the highest at 35.16 kJ/mol, whereas in silica gel with air humidity of 0.007 kg/kg d.a. (750 lpm), it is the lowest at 22.92 kJ/mol. Meanwhile, the dryer air flow rate, higher heater temperature, and lower air humidity improve the performance of the bed dryer against its evaporation rate and decrease the Specific Energy Consumption (SEC) value. SEC is also greatly influenced by the use condenser 1, which provides heater power savings of up to 79.1%. Thus, the system is expected to be applied to commercial drying systems that can work at low drying temperatures to maintain drying products and obtain low energy consumption.
干燥方法需要付出努力来将食物储存更长时间。一些干燥过程存在技术和经济方面的弱点，主要与效率低下、能源成本高以及产品质量下降有关。人们已经研究了各种干燥模型，以确定在使用不同材料的空气除湿方案中，传热传质分析在干燥速率方面的适用性，其中一种材料是硅胶。在这种情况下，研究人员使用配备制冷系统的填充床干燥器，研究了湿度、温度和气流速率对硅胶中水脱附的恒定干燥速率和活化能的影响。这种改进后的系统旨在降低比能耗（SEC）。结果表明，硅胶中水脱附的恒定速率以及空气湿度的增加会导致硅胶中水脱附速率的恒定值降低。然而，温度和气流的增加会导致硅胶中水脱附的恒定干燥速率值增加，因为它们会引起毛细管蒸发。同时，硅胶中水脱附的活化能随着气流速率的降低和进气湿度的增加而增加。如果气流速率降低或空气湿度增加，作用在水分子上的来自周围壁面表面力场的吸引力会变得更强。从结果和分析可以看出，在空气湿度为0.013 kg/kg d.a.（450 lpm）且气流速率较低的情况下，硅胶中水脱附的活化能最高，为35.16 kJ/mol，而在空气湿度为0.007 kg/kg d.a.（750 lpm）的硅胶中，活化能最低，为22.92 kJ/mol。同时，干燥器的气流速率、较高的加热器温度和较低的空气湿度提高了床式干燥器的蒸发速率性能，并降低了比能耗（SEC）值。SEC也受到冷凝器1使用的极大影响，冷凝器1可节省高达79.1%的加热器功率。因此，该系统有望应用于能够在低温干燥条件下工作以保持干燥产品并实现低能耗的商业干燥系统。
