Thermal design of a hydrogen heater for an air turboramjet engine

A compact heat exchanger has been designed for an air turboramjet engine proposed for future spacecraft. Hydrogen fuel is heated by the combustion gas of the engine at the heat exchanger. The heat exchanger, called a hydrogen heater when used in an aircraft, has to be compact so that when it is set in an engine duct to enhance heat transfer it will cause a small increase in the pressure loss of the combustion gas. To endure the vibration caused by combustion gas turbulence and the high pressure of hydrogen fuel flowing in the heat exchanger, inline tangential tube banks are adapted. An optimum design point of the heat exchanger is shown that is calculated by use of results of fundamental experiments on the heat transfer of inline tangential tubes. A small heat exchanger is developed and loaded into an ATREX500 type engine, a sea-level static air turboramjet engine used to check the predicted thermal performance of the heat exchanger. Experimental results almost match the engine system requirements and show the possibility of developing a flight-model heat exchanger.