Elangovan Elavarasan, Natarajan Sendhil Kumar
Department of Aerospace Engineering, SJC Institute of Technology, Chikkaballapur, Karnataka, 562101, India.
Department of Mechanical Engineering, National Institute of Technology Puducherry, Karaikal, U.T of Puducherry, India.
Environ Sci Pollut Res Int. 2023 Jan;30(4):10469-10483. doi: 10.1007/s11356-022-22865-5. Epub 2022 Sep 8.
In the present work, a study on convective heat, mass transfer coefficients and evaporative heat transfer coefficient of the thin layer drying process of ivy gourd is performed. The experiment was conducted in three drying modes such as natural, forced convection solar dryer and open sun drying. The hourly data for the rate of moisture removal, sample temperature, relative humidity inside and outside the solar and ambient air temperature for complete drying have been recorded. The drying air temperature varied from 55, 65, 70 and 75 °C, and the air velocity was 1, 1.5 and 2 m/s. All the drying experiments had shown a falling rate period. The data obtained from experimentation have been used to evaluate the experimental constant values of C and n by simple regression analysis. Based on the values of "C" and "n", convective and evaporative heat transfer coefficients for ivy gourd were determined. The average convective heat and mass transfer coefficients varied between 2.64 and 8.30 W/m °C and 0.0025 to 0.0076 m/s for temperature ranges, at the different air velocities, respectively. The average evaporative heat transfer coefficient for ivy gourd varied from 181.89 to 421.84 W/m °C. It was observed that convective and evaporative heat transfer coefficients increase with the increase in drying air temperature. The rate of increment of evaporative heat transfer coefficient is higher than the convective heat transfer coefficient. The intensity of heat and mass transfer during solar drying depends on the drying air temperature and velocity.
在本研究中，对苦瓜薄层干燥过程的对流换热系数、传质系数和蒸发换热系数进行了研究。实验在自然干燥、强制对流太阳能干燥器和露天晾晒三种干燥模式下进行。记录了整个干燥过程中每小时的水分去除率、样品温度、太阳能干燥器内部和外部的相对湿度以及环境空气温度的数据。干燥空气温度为55、65、70和75℃，风速为1、1.5和2m/s。所有干燥实验均呈现降速阶段。通过简单回归分析，利用实验获得的数据评估了C和n的实验常数值。基于“C”和“n”的值，确定了苦瓜的对流换热系数和蒸发换热系数。对于不同的风速，在不同温度范围内，平均对流换热系数和传质系数分别在2.64至8.30W/m²·℃和0.0025至0.0076m/s之间变化。苦瓜的平均蒸发换热系数在181.89至421.84W/m²·℃之间变化。观察到对流换热系数和蒸发换热系数随着干燥空气温度的升高而增加。蒸发换热系数的增加速率高于对流换热系数。太阳能干燥过程中的传热传质强度取决于干燥空气温度和风速。
