Working Principle of Hot Air Drying for Chili Segments

The core principle of hot air drying for chili segments is: using hot air as the drying medium, transferring heat to the chili segments through convective heat exchange, causing internal moisture to migrate to the surface and evaporate, and then having the flowing air carry away the water vapor, thereby achieving continuous dehydration and drying.

This can be understood from the following aspects:

Basic Processes of Heat and Mass Transfer

1. Heat Transfer

Hot air drying equipment heats air through a heat source (steam, electricity, natural gas, biomass, or heat pump) to form hot air at 40–80°C. Driven by a fan, the hot air flows over the surface of the chili segments, transferring heat to the material through convective heat exchange. After the chili segments absorb heat, the temperature of the internal moisture rises, and it begins to migrate toward the surface.

2. Moisture Migration

Under the action of concentration differences and temperature differences, the moisture inside the chili segments diffuses from internal high-moisture areas to surface low-moisture areas. After reaching the surface, the moisture absorbs latent heat of vaporization, changes from liquid to gas, and leaves the material surface.

3. Water Vapor Discharge

The evaporated water vapor is carried away by the flowing hot air and discharged from the drying room or dryer through a moisture exhaust fan. If moisture removal is poor, the humidity inside the drying chamber rises, which inhibits further moisture evaporation and reduces drying efficiency.

Multi-Stage Temperature Control Process (Key for Chili Segments)

Chili segments have a high moisture content (fresh chili is about 80%) and are rich in capsaicin and volatile aroma components. During drying, a multi-stage variable temperature process must be adopted to avoid high temperatures causing decomposition of capsanthin, darkening of color, and loss of spiciness.

Hot Air Circulation Mode

Chili segment hot air dryers usually adopt a forced hot air circulation design:

- Hot air penetrating the material layer: Hot air vertically penetrates the chili segment layer from below or the side of the mesh belt, ensuring each segment is evenly heated.

- Multi-layer mesh belt turning: Chili segments turn and fall layer by layer between the multi-layer mesh belts, allowing internal and external moisture to evaporate synchronously and avoiding local over-drying or over-wetting.

- Partial exhaust gas recycling: The discharged humid hot air still contains a large amount of heat. Through a waste heat recovery device, part of the exhaust gas is reintroduced into the drying chamber, which can significantly improve thermal efficiency and reduce energy consumption.

Hot air drying of chili segments is essentially the simultaneous operation of three processes: "convective heat exchange + moisture migration + vapor discharge." Through multi-stage temperature control and forced hot air circulation, it efficiently dehydrates while maximizing the retention of the chili's bright red color, spicy flavor, and aroma components. It is the mainstream drying method for large-scale processing of chili segments.