Transient Humidity Measurements: Part II—Determination of the Characteristics of an Interactive Device

In this paper, a humidity/temperature transmitter is used to determine the transient response characteristics of a passive interactive moisture transfer device (i.e., a desiccant coated energy wheel) following a step change in humidity and temperature. The output of the transmitter, which is placed downstream of the energy wheel, follows exponential functions with two time constants and includes the combined effects of the device and transmitter. The response of the unknown device needs to be deconvoluted from the measured data to determine the transient characteristics of the device alone. The results in this paper show that the transient moisture characteristics of the interactive device are strongly influenced by the temperature testing conditions. Isothermal test conditions are recommended when determining the moisture characteristics of devices that have a combined heat and moisture transfer interaction