Buckwheat is a globally recognized, nutritionally rich crop with robust adaptability, serving as a multi-purpose plant for its health benefits. Achieving precise and mechanized plot seed harvesting is a critical step in obtaining accurate results in breeding experiments. However, plot breeding requires no seed retention, no mixing, and ensures no accumulation of seed in the threshing unit. A self-cleaning technology was developed to prevent seed retention, mixing, and accumulation in the multistage tangential cylinder threshing unit. The newly designed cleaning system has five air inlets and a centrifugal fan for pneumatic cleaning. CFD simulations were conducted for each inlet position, coupled with four varying inlet velocities and the rotation speed of the main threshing cylinder. During the post-processing stage of the CFD modeling, a line consisting of fifty points was drawn beneath the threshing drums, and the air velocity at these points was recorded. The optimal configuration of inlet position, inlet air velocity, and main threshing drum rotation speed for efficient cleaning was identified based on the ratio of points beneath the drums where the airflow speed surpassed the suspension speed of buckwheat to the points where the airflow speed was lower than the suspension speed of buckwheat. The optimal configuration for "inlet_1" was identified based on the suspension velocity of buckwheat grain, with an inlet velocity of 4 m/s and a main threshing drum speed of 450 rpm.

This study presents a comparative experimental and numerical investigation of two solar air heater (SAH) configurations: a flat-panel absorber (F-SAH) and a longitudinal-baffle absorber (LB-SAH). Experiments were conducted under real outdoor conditions at mass flow rates of 0.00410, 0.00513, and 0.00616 kg s⁻¹, and a three-dimensional CFD model was developed in ANSYS Fluent using the SST k–ω turbulence closure. The numerical results showed excellent agreement with experimental data, with a mean deviation not exceeding 4.5%. The LB-SAH consistently outperformed the F-SAH across all operating conditions. For experimental results, the maximum outlet air temperature reached 97 °C for the LB-SAH compared to 79 °C for the F-SAH at a mass flow rate of 0.00410 kg s⁻¹. The thermal efficiency of the LB-SAH ranged from 47.76% to 64.51% as the mass flow rate increased from 0.00410 to 0.00616, compared to 30.77–47.76% for the F-SAH. The LB-SAH achieved Nusselt numbers up to 110.18% higher than those for the F-SAH, with heat transfer coefficients of up to 16.61 W m⁻² K⁻¹. The thermohydraulic performance parameter (THPP) reached 1.49 for the LB-SAH configuration at m = 0.00616 kg s⁻¹, confirming significant net energy gains compared to the results for the F-SAH configuration. These findings establish the LB-SAH as the superior configuration in terms of thermal performance, while highlighting the F-SAH as the preferred choice when minimizing hydraulic resistance is a priority. While the LB-SAH significantly enhances heat transfer performance, this improvement is accompanied by an increased pressure drop and higher fan power requirements.