CFD Optimization of Air Supply Angle and Rack Layout for Straw Mushroom

Air distribution uniformity is critical to the quality and yield of straw mushrooms (Volvariella volvacea); however, the coupled effects of air supply angle and cultivation rack layout remain poorly understood. We developed and validated a steady-state CFD model for a straw mushroom house with an active return-air heat pump system. Model validation against field measurements showed mean relative errors of 7.2%, 9.5%, and 1.1% for in-duct velocity, outlet velocity, and temperature, respectively confirming reliability of the model. Four scenarios were then simulated, combining horizontal (0°), vertical (90°), and mixed supply angles with two or three rack rows. The two-row layout with vertical downward supply (2-90°) achieved the best overall performance, attaining a vertical velocity CV of 8.7% and optimal-zone area ratios of approximately 90% across all layers. The mixed supply (2-0°+90°) showed intermediate performance (vertical velocity CV = 13.7%), whereas the horizontal cases (2-0° and 3-0°) exhibited pronounced wall-attachment effects, with vertical velocity CVs of 42.2% and 26.7%, respectively. An AHP-entropy-weighted TOPSIS evaluation further confirmed the superiority of the schemes incorporating a vertical component, with 2-90° ranking highest. These findings indicate that vertical downward supply combined with a two-row layout markedly improves environmental uniformity, providing practical guidance for the ventilation design of similar intensive mushroom cultivation facilities.