Volume 68

Simulation of a Chilled Water System Based on MWorks and Its Application for Commissioning Xuan Zhou, Yuhao Fang, Xinhua Xu, Junlong Xie, Jiaming Xiong

Abstract

In existing buildings, the efficiency of air-conditioning water systems is frequently constrained by flaws in de-sign, installation, and control, resulting in substantial en-ergy waste and poor operational performance. This re-search centers on the severe hydraulic imbalance in the main branches of such systems within an industrial sys-tem. It usually causes inadequate cooling capacity in the coils located upstream of AHUs. Additionally, the lack of permanent sensors complicates on-site hydraulic balance adjustments. To resolve these challenges, a hydraulic balancing method based on simulation technology is pro-posed. Specifically, a physics-based simulation model is constructed in MWorks using the Modelica language. Validated against historical operational data, the model exhibits relative errors of less than 3% for flow rate and 6% for pressure drop, thereby showing excellent con-sistency with the actual hydraulic characteristics of the system. A PID-based control strategy is integrated into the simulation model to calculate target valve openings for key branches. These computed values offer direct, quantitative guidance for on-site manual adjustments, eliminating the need for a permanent sensor network. Moreover, AHUs continue to operate normally even when the pump frequency is reduced by 2 Hz, which indi-cates enhanced overall system performance and energy efficiency. This study presents a practical, low-cost digital twin approach for retrofitting existing HVAC systems, underscoring the effectiveness of Modelica-based physi-cal modeling in the analysis and control of intelligent en-ergy systems.

Keywords Commissioning, industrial systems, hydraulic imbalance, MWorks