Abstract
The aim of the present work is to study the static and the dynamic behaviors of parallel and counter flow heat exchangers controlled by manipulation of flow rate. It is shown that PI-feedback control system has a unique steady state. The PI-feedback control system has an unstable region in which the limit cycle is caused by the nonlinearity of the manipulation of flow rate rather than by the valve saturation. The stable region may be determined by a parameter plane method. Experimental results verify the existence of the limit cycle and agree well with the theoretical calculation.
