Through-air drying of tissue and towel grades

A computer model that simulates the sheet drying part of through-air drying of tissue and towel grades has been developed. Empirical relationships for heat and mass transfer coefficients show that a simple, single relationship covering a wide range of through-drying conditions is not adequate. However, several empirical relationships, each covering a narrow range of process conditions, are more accurate. Experimental data that represent commercial operating conditions are critical in developing a comprehensive system simulation. Results to date indicate that, under the conditions studied, the sheet temperature quickly warms up to the saturation temperature and remains constant for a long time before beginning to rise at the end. The sheet drying rate primarily consists of on increasing rate period and a falling rate period. Application: A computer model could be used to evaluate ways to reduce energy consumption in new through-drying systems.