Wing Fuel-Tank Heat-Sink Calculation for Conceptual Aircraft Design

Abstract

The utilization of fuel as a heat sink can enable the design of higher-performance aircraft through the reduction of heat loads. A conceptual design phase energy model for the cross section of a wing with an internal fuel tank is developed for computing the rate of heat rejection in flight. The calculations focus on physical dependencies rather than empirical correlations, solving the conservation of energy equation by using results from prior solved conservation of mass and momentum equations. A series of control volumes and various temperature profiles are employed to model the thermal boundary layer. The surface boundary conditions include an isothermal surface as well as an unheated starting length to approximate a heated fuel tank. An implicit root-finding method is verified and used in solving the resulting system of equations. Results are compared to empirical correlations for validation purposes involving laminar and turbulent flow test cases over a flat plate, various NACA airfoils, as well as a C-130 Hercules. Two temperature profiles are considered and compared throughout the verification and validation process. The results show reasonable agreement with empirical correlations, and thus show great promise to be employed in conceptual design.