Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: January 11, 1996
Publication Date: N/A
Interpretive Summary: Vapor pressure is the fundamental driving force for moisture changes in cotton, the attraction for cotton for moisture is a temperature dependent manifestation of vapor pressure. Data from drying system tests and equilibrium moisture level data was used to relate moisture levels to vapor pressure of cotton and air in the dynamic temperature conditions in gin dryers. Areas of incomplete data were shown and designs for tests needed to develop the data were suggested. With a complete profile of the dynamic temperature and vapor changes in cotton drying systems the most efficient and effective processes for conditions encountered could be designed. This would save the ginning industry energy costs and also would enable high efficiency cleaning of cotton without using conditions that now cause fiber damage.
Technical Abstract: Cotton gin drying systems were mathematically modeled using calculations based on laboratory data showing drying rates for small samples. The model was used to predict expected moisture transfer rates for different components of machine-stripped cotton in typical cotton gin drying systems. The calculated results were compared with actual results for two types of gin drying systems. The source of apparent rewetting that has been noted in seed cotton downstream of gin drying systems was examined using vapor pressure relationships. Possible ways for modifying drying processes to compensate for drying rates, and to maintain the drying gradient are suggested. The results show that some rethinking of cotton gin drying processes is in order and additional research is needed. Fundamental data showing vapor pressure for cotton in terms of temperature and moisture level is needed so that it can be integrated with vapor pressure and temperature data for air to describe the interactions through the entire drying system and allow design of ways to compensate for imbalances originating from the drying process.