Dryer for a textile material web having a device for determining the residual moisture of a material web and method, module, and system therefor

A method for operating a dryer for a web of textile material with at least one dryer compartment, comprising steps of:

• rotatably disposing in the dryer compartment at least one air-permeable cylinder around which the web of textile material partially loops;
• flowing a drying heated fresh air flow through the web of textile material;
• suctioning off through a duct with at least one fan humid drying air as discharge air from an inside of the at least one air-permeable cylinder from a front-sided opening of the at least one air-permeable cylinder;
• detecting values of at least a temperature and a humidity of the fresh air flow;
• detecting a value of a temperature, a volume flow rate and a humidity of the discharge air;
• detecting values of at least a mass flow rate and a humidity of the web of textile material entering the dryer;
• inputting into a control a value for a reference variable for a desired residual humidity of the web of textile material;
• calculating an evaporative capacity of the dryer from the detected values in a control;
• and
• upon deviation of the evaporative capacity of the dryer from the reference variable, controlling at least one of the at least one heating element and the at least one fan while selectively considering at least one of an energy optimization and a cost optimization.