Since the introduction of Hydrazine to the list of substances of very high concern, REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals), there has been an increase in the investigation of “green” propellant alternatives. At the DLR Institute of Space Propulsion, a mixture of Nitrous Oxide
and Hydrocarbons (Ethylene or Ethane), called HyNOx, has been under development since 2014. These monopropellants offer bipropellant-like performance, the ability to be used in a self-pressurised propulsion system, and are non-toxic. HyNOx propellants have the drawback of high combustion temperatures (up to 3400 K). Therefore, it is necessary to study what cooling methods can be applied to rocket engines using HyNOx propellants.
During this project, the test setup, HTMS (Heat Transfer Measurement Section), has been designed, built and tested in the M11.2 test bench at the DLR Lampoldshausen to study heat transfer in regeneratively cooled channels. The design was based on what was learned from studying past experimental
setups. A test campaign was performed to study the use of Nitrous Oxide and Ethane as coolant in stainless steel, copper and aluminium alloy pipes of different diameters. The setup diagnostics system was improved by procuring new measurement instrumentation. Additionally the instruments were
installed in different ways in order to understand which method would provide the most accurate and reliable results. The results of the thesis show that Ethane has better coolant properties than Nitrous Oxide due to its higher specific heat. However, the carbon present in Ethane leads to the formation of carbon deposits at high temperatures which can lead to clogging of the pipes and therefore Nitrous Oxide could be a the preferred coolant for situations where the temperatures are high enough for carbon deposition to occur. Additionally, it was determined that pure copper and the aluminium alloy AlMgSi 0.5 are not adequate materials for the construction of cooling channels. In the course of this project and to complement the experimental testing, a Matlab-based numerical simulation tool was developed that simulates the temperature profile in the HTMS setup using empirical Nusselt correlations to determine the heat transfer coefficient.