Thermodynamic Driver
Gradient variables representing the difference in moisture concentration between a fabric surface and the drying air drive the rate of water removal. The differential partial pressure of water vapor determines the direction and speed of the moisture transport during the drying phase. It is calculated as the difference between the saturated vapor pressure at the wet fabric temperature and the partial pressure in the circulating air.
This gradient is the fundamental force behind all drying processes.
Evaporative Mechanism
Evaporation continues as long as the surrounding air is not saturated and has a lower vapor concentration than the wet textile. A higher differential partial pressure increases the rate of mass transfer, which accelerates the stenter operation. This driver is manipulated by adjusting either the fabric temperature or the humidity of the drying air.
Reducing the exhaust air humidity is a common method to maintain a high gradient.
Stenter Setting
Controlling the moisture level in the circulating air of a drying chamber allows operators to maintain a consistent evaporation rate. If the differential partial pressure drops too low, drying slows down and fabric may exit the machine damp. Humidity sensors track the air composition to adjust the fresh air intake and exhaust dampers automatically.
This ensures that the drying driving force remains within the target range.
Equilibrium Boundary
When the fabric moisture content falls below the fiber saturation point, the vapor pressure of the moisture decreases. This reduces the driving force and slows down the drying rate.
