Automatic Generation of Pipe Routing for Variable Refrigerant Flow Air Conditioning System

The traditional design of variable refrigerant flow (VRF) air conditioning system relies heavily on the expertise and experience of designers. Designers spend considerable time modifying the drawings to accommodate design alternations. This paper aims to develop an automated routing method for refrigerant piping in VRF systems, based on building information modeling (BIM). The proposed methodology includes automatic zoning of the VRF system, automatic layout of indoor units, and automatic generation of refrigerant piping. To achieve system zoning, a combination of hierarchical clustering and rule-based methods are employed, while a geometric recognition method is utilized for the obstacle-avoiding layout of the indoor units. The escape graph method is applied for spatial modeling, and an ant colony optimization (ACO) approach with a concurrent search strategy is applied for multi-objective path optimization. This approach facilitates the automatic generation of the optimal orthogonal branch pipe route while ensuring obstacle avoidance. Moreover, a breadth-first search (BFS) approach is employed, considering 12 potential forms of divergence tube connections within the pipeline, which are sequentially integrated into the pre-generated piping layout. This paper presents the results of testing conducted on two engineering buildings modeled in Revit. The outcomes align with engineering standards, thus demonstrating the feasibility of the proposed method. Compared to traditional manual drafting, this automated method can complete the piping layout in just a few seconds, significantly reducing design and drawing time. This advancement further enhances the level of intelligence and automation in the heating, ventilation, and air conditioning (HVAC) system design.