A Distributed Algorithm for Auto-balancing of Hydronic Cooling Systems

Hydronic cooling systems are often used in large buildings. In these systems, chilled water is transported from the chillers to Air Handling Units (AHUs) via a water distribution system. The temperature of exhaust air is controlled by the flow of the chilled water in AHUs. Due to a poorly balanced hydronic network, some of the AHUs may experience starvation at high load conditions, meaning that air temperature control is impossible. To overcome this problem, we propose an automatic approach to balancing the hydronic system, such that all AHUs can control their air temperatures. The cost is that all zones of the building are controlled to a slightly higher air temperature, which often can be compensated by higher air flow, to keep the room temperature at the desired value. The balancing algorithm is verified on a Modelica model of an office building.