The discussion about energy takes a central role, whether it is about energy security, energy cost or the transition to renewable energy. An often overlooked part however is that most of this energy comes in the form of heat. It can, amongst others, be solar heat, process heat and geothermal heat. When talking about heat, one of the first questions that arises is how to efficiently transfer heat. For many applications this has been thoroughly investigated in scientific literature. Some of these applications are for example heat pumps, thermal power plants and refrigeration cycles. However now a new technology is emerging which can effectively convert low-temperature heat to electricity, the Organic Rankine Cycle (ORC). While the ORC inherently has a low efficiency, it can be greatly improved by implementing heat transfer at supercritical conditions. From other applications it is known that under supercritical conditions the fluid properties and physical mechanisms of heat transfer vary strongly. This has a huge impact on the design and control. Unfortunately, for the specific working fluids and operating conditions of an ORC no data is available to investigate this. This work aims to provide this data and to derive a robust and accurate heat transfer model. If this gap in scientific literature is filled, it would have the potential to launch the development of supercritical ORCs resulting in both increased energy efficiency and increased shares of renewable energy.