###### Abstract  
Previous research has shown that the accumulated temperature can describe drying processes as well as crop growth. To describe the mass and heat transfer processes in the rice drying process more accurately, a mathematical model of rice drying was proposed based on the drying accumulated temperature, and the optimal tempering ratio for conventional hot air drying was obtained through data comparison and analysis. First, it was proven that there was an exponential relationship between the moisture ratio and the drying accumulated temperature of rice. Second, by comparing and analyzing the fitting results of seven different drying mathematical models, the model with the highest fitting degree was selected and reconstructed to obtain the drying accumulated temperature-moisture ratio model. Finally, the new model was used to fit the results of two drying experiments without and with tempering, and the tempering characteristics of rice drying were proved by comparing and analyzing the coefficient difference between the two models. The results showed that the optimal tempering ratio was 3. This study thus provides a reference for rice drying process parameters. drying accumulated temperature; moisture ratio; rice; tempering Article  
Characteristics Based on Drying Accumulated Temperature  
[PERSON], [PERSON], [PERSON], Z. To improve the above situation, many new and more accurate sensors and gauges have been introduced in recent years to record more comprehensive data or enhance control systems, which makes building new models more challenging [7]. The [PERSON] model [8], proposed by [PERSON] in 1949, has had a profound influence on field of drying. The [PERSON] model [9] is an exponential model that is also widely used in the field of drying, which uses [PERSON]'s law of cooling to describe moisture motion. The [PERSON] model [10] is another exponential model, which has a better fitting effect than the [PERSON] model in some cases. [PERSON] [11] proposed two single-parameter equations to quantify the thin-layer drying characteristics of contemporary long-grain rice cultivars grown in the Mid-South U.S. The results showed that the two equations have a high degree of fitting, with the shortcoming that only two drying parameters, hot air temperature and relative humidity, were taken as the influencing factors. [PERSON], et al. [12] carried out an orthogonal experiment involving hot air drying with variable temperature and humidity and established a comprehensive target model; the drying process was optimized by a genetic algorithm. [PERSON], et al. [13] used empirical and diffusion models to describe rice drying kinetics, and considered only effective time of operation to compare and evaluate continuous and intermittent drying of rough rice. This study proved that a one-dimensional diffusion model could describe the drying process of rice properly, and found that the effective mass diffusivity was higher in intermittent drying as compared to continuous drying at the same temperature. The models established in the above studies can describe the grain drying process to a certain extent; however, there is still room for improvement in the model accuracy. Rice is a kind of heat sensitive material which requires a high drying process [6; 14]. Intermittent drying is used in conventional rice drying around the world; it is considered one of the solutions to improve the energy efficiency and post-drying quality of rice without increasing drying cost, and has good research and promotional prospects. This technique reduces possible damage in the form of cracks, minimizes energy costs, and provides better final product quality [15]. The most common form of intermittent drying is alternating drying and tempering. Tempering refers to placing rice in a relatively confined space for a period of time without human intervention in order to balance the moisture gradient and reduce thermal stress between grains and within grains [16; 17].