An integrated heat-transfer-fluid-dynamics-mass-transfer model for evaluating solar-dryer designs

This work aims to facilitate the design-improvement process of solar dryers by a computational model that accounts for the interrelationships between the conditions of the drying product (temperature and moisture content), the airflow inside the dryer (temperature, humidity, and velocity), and the surrounding conditions (temperature, humidity, and solar radiation). The model considers not only how the dryer and surrounding affect the drying of the product but also how the conditions of the product itself affect the conditions of the airflow inside the dryer and, by extension, its performance as well. To account for such intricate interrelationships, the model leverages and integrates three physical domains: fluid dynamics, heat transfer, and mass transfer. The model automatically simulates the natural convection inside the dryer and eliminates the need for obtaining the experimental values of the temperature, humidity, and velocity of the internal airflow for calculating the moisture level of the product. It can be used to quantify the effects of mixed-mode solar dryer designs on their drying performance. Simulated results were validated against experimental data and found to be reasonably accurate. Moreover, the model offers insights into how the complex airflow inside the dryer can affect the drying of the product. Practical applicationsExperiments that are required to understand, compare, and improve the drying performance of different solar dryer designs can be impractical because of long operation time of solar drying and variability of weather conditions, making a typical design process time-consuming. This work aims to facilitate the design-improvement process. The model can quantify the effects of mixed-mode solar dryer designs on their drying performance. The model can also offer useful insights for solar-dryer designers. For instance, results from a case study show that the velocity and humidity of the internal airflow could have stronger influence than that of the temperature on the drying, suggesting that a solar dryer design that aims only to maximize airflow temperature may not lead to optimal drying, and that airflow temperature should not be used as the sole benchmark for solar dryer design.