Dynamics of two-heat exchanger network

The dynamics of heat exchanger networks, parallel and series connections of two heat exchangers are investigated. Experiments of two steam-condensers cooled by water in tubes are performed and show intersting phenomena on both parallel- and series-heat exchanger networks. The characteristics of the parallel systems are mainly influenced by a stream splitting, i.e., the flow rate distribution and the transportation lag-time in the pipe connecting each heat exchanger and a confluence point. The magnitude and phase of water (cold stream) outlet temperature change against a water flow rate change input show fluctuations in the lower frequency range. In the same manner, the magnitude and phase of the series systems also show a fluctuation in a lower frequency range. These behaviors are caused by the effect of the size ratio of the primary heat exchanger to the secondary one and the lag-time in the pipe connecting each heat exchanger. Consequently, it is clarified that both the parallel and series systems are sensitive to the transportation lag-time in the pipe. The results shows the importance of a fluid transportation model in the pipe on the dynamics of the system.