Hardware-in-the-Loop (HIL) simulation and testing is a technique that combines real hardware components with a software model that simulates part of the system environment with which the hardware interacts. This implies that the software model is able to supply the calculated output results and interact with the hardware in real time. For a thermo-fluid simulation model this is not always the case with simulations running either faster or slower than real time depending on the complexity of the system being modelled. In another scenario, a commercial operations team may require to understand a system’s behaviour quickly and easily, as non-experts, by using a runtime version of the full simulation model. This paper describes the Design of Experiments approach used in Flowmaster V7 that enables meta-models of a full simulation model to be exported as C code or as MATLAB™ S-Functions suitable for use in an HIL environment or as the backend code to a runtime model of the system.