Abstract
High temperature steaming with humid air is important in textile printing.
In this report, the heat conduction of paper cylinder, used as a model of yarn, was investigated under various conditions of high temperature steaming with humid air. The temperature was recorded by inserting Alumel/Chromel thermocouple into the cylinder.
The results obtained were as follows.
1) The temperature rise of a paper cylinder during the steaming with humid air was characterized by three periods, i.e. the period of heating by latent heat of condensed water, that of constant temperature heating by reevaporation of condensed water and that of heating of dried fiber. Such periods could not be clearly observed on the nonporous cellophane cylinder. These results suggested that in a cellophane cylinder the condensed water was retained only on the surface, whereas in a paper cylinder the steam penetrated into the cylinder. Therefore, the porosity of the fiber assembly played an important role on the heat conduction and the water condensation during the steaming.
Generally, there is following relation between heating medium and heated material
In T0/Tt=kθ
where, T0: initial temperature difference
Tt Temperature difference at time θ
θ: heating time
k: constant
From the above equation, it is expected that the plot of In T0/Tt against θ is linear. But in the case of paper cylinder, the relation between In T0/Tt and θ was expressed by three parts of creased line. The time intervals of heating by latent heat and by the reevaporation of condensed water were estimated from the creased lines on the graph.
2) The rate of temperature rise on the cylinder surface during the heating by latent heat was estimated by extraporation to zero diameter. The obtained results were compared with a parameter of temperature rise, In (T0/Tt)/θ .
