Simulation models are crucial for various applications across the lifecycle of process plants, such as plant engineering. As the industry moves toward modularization, plant components are increasingly supplied by manufacturers who design these modular units, often called package units or process equipment assemblies. Consequently, critical knowledge about their behavior resides with the manufacturers. This paper outlines the requirements for simulation model exchange to share this behavioral knowledge. It reviews solutions and highlights challenges based on literature and case studies. Key elements include metadata, open standards, IP protection, and quality assurance. Solutions, like the asset administration shell (AAS), CAPE-OPEN, the Functional Mock-up Interface (FMI), encrypted models, and quality models, are discussed. Remaining gaps are highlighted.