An Evaporative-Gravity Technique for Airborne Equipment Cooling

In airborne electronic packages, for either thermal or electrical reasons cooling air often is not ducted directly over the components but is passed through a heat exchanger. Consequently, the thermal path between the heat exchanger and the components must be of low impedance to result in efficient heat transfer. The high heat transfer coefficients obtainable as a liquid boils and condenses permit an effective reduction of the temperature drop between the electronic components and the heat exchanger. In this paper the development and design of an evaporative system utilizing gravity return flow is discussed, and the test results of such a system are compared with those obtained utilizing a conventional metallic conductive paths technique. Where heat dissipation or cooling air inlet temperature is high, the evaporative-gravity (ev-grav) system is shown to be the most effective.