Mode-Dependent Time Constants in Electric Heating Processes

Adequate comfort conditions in any space heating process can be assured only if a good understanding of the dynamic temperature variations is possessed. The vast majority of published literature considering the system dynamics assumes that the temperature variations have an exponential increase or decrease with time, and hence, that the thermal system can be modeled by linear RC equivalent circuits. These linear models have a severe restriction in that the time constant of the exponential variations remain constant under all conditions. A few published articles giving experimental data have indicated that in discontinuously controlled electric heating processes the system time constant during heating (active time constant) is not necessarily the same as the system time constant during the interval in which no heat is supplied (passive time constant).