Functional materials’ properties are influenced by microstructures which can be changed during manufacturing. Experimental characterisation is often time consuming and expensive. A technique is presented which digitises graphite foam via X-ray tomography and converts it into image-based models to determine properties in silico. By simulating a laser flash analysis its effective thermal conductivity is predicted. Results show ~3% error in two of three planes but is significantly less accurate in the third due to effective thermal conductivity resulting from both the foam’s microstructure and graphite’s crystallographic structure. An empirical relationship is found linking these by using a law of mixtures. A case study is presented demonstrating the technique’s use to simulate a heat exchanger component containing graphite foam with micro-scale accuracy using literature material properties for solid graphite. Compared against conventional finite element modelling these is no requirement to experimentally measure the foam’s effective bulk properties. Additionally, improved local accuracy is achieved due to exact location of contact between the foam and other parts of the component. This capability will be of interest in design and manufacture of components using graphite materials. The software used was developed by the authors and is open source for others to undertake similar studies.