Effect of installation factors on the environment uniformity of multifunctional fan-coil unit system in Chinese solar greenhouse

Airflow significantly affects crop growth, and providing adequate and uniform airflow is essential to improve crop yield and quality. This paper used computational fluid dynamics software to optimize multifunctional fan-coil unit (FCU) installation factors at different crop heights. Fan pressure jump coefficient got optimized further, and the percentage of disturbance velocity was proposed as an index to evaluate the improvement of turbulence characteristics in airflow fields. The simulation results showed that the FCU system's optimal tilt angle, swing angle, and height above the ground were 20°, 45°, and 2.9 m, respectively. The optimum spacing is related to crop height. For lower tomatoes, the optimal spacing was 4.2 m and 4.5 m for higher tomatoes. The velocity coefficients of variation (Cv-v) for different height crops before optimization were 0.58 and 0.66. The Cv-v after optimization decreased to 0.37 and 0.41, and the uniformity was improved by 36.21 % and 37.88 %; the porous medium amounts percentage in the optimum air velocity range were increased to 64.70 % and 23.50 %. Simultaneously, the homogeneous airflow distribution improved the temperature field uniformity by 46.5 % and 23.95 %. This paper can provide theoretical guidance for the design and installation of FCU systems.