On-Board Thermal Management of Waste Heat from a High-Energy Device

The use of on-board high-energy devices such as megawatt lasers and microwave emitters requires aircraft system integration of thermal devices to either rid waste heat or utilize it in other areas of the aircraft. Non-chemical lasers are among the most challenging applications due to the low cooling temperature requirements (67 -F) and high waste heat generation times of order 20 s. (Microwave devices will be cooled at 157.7 -F.) One plan calls for the rapidly generated waste energy to be stored prior to peripheral utilization, with subsequent removal of the heat over a 5-10 minute span. A method is presented that explores the primary factors in a laser-generated waste heat removal system to allow an understanding of the trade space between the laser power, overall thermal efficiency , and the duty cycle. Methodology includes incorporation of a single heat pump or cascaded heat pumps that transfer waste heat from the high-energy device into the bypass section of a mixed-bypass turbofan jet engine. Analyzed are multiple heat exchanger configurations that do not block the bypass air flow, minimizing friction losses. Some particulars of the waste heat removal system include a water coolant for the heat pump(s) and a maximum coolant temperature limited to 2,270 R. Results of an engine performance model used to determine the impact of the thermal management system are also presented.