Hydraulic networks constitute a fundamental part of heating, ventilating and air conditioning systems in buildings and high rises. In order to optimize large and complex networks it is important to understand the effects of operational changes in one loop on the others. The objective of this study is to investigate the time-independent flow and thermal interactions between secondary user-loops, in a hydraulic network that is used for cooling, when the system goes from one steady state to another. The study is experimental and was carried out on a facility which has a primary cooling loop, three secondary loops, and a primary heating loop. The flow was abruptly changed by actuating a valve in one of the loops causing changes in the other two loops. Results show that the change of flow rates and pressure differences in the other two loops are linearly dependent on that in the actuating loop. The dependence is also affected by the initial operational condition of the network. The thermal interaction, however, is different in that it is nonlinearly coupled with the hydrodynamic interaction.

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