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The effects of elevated acceleration fields on spray cooling heat transfer are discussed in this paper. Spray cooling has proven to be one of the most efficient methods of heat removal. This technology is being transitioned into more advanced applications, such as fighter aircraft that must withstand a wide range of variable acceleration-induced body forces. Heat transfer associated with closed-loop spray cooling will be affected by acceleration body forces, the extent of which is not yet known. To test these various effects, an eight-foot-diameter centrifuge table will be outfitted with a spray cooling system to test for the effects associated with elevated gravity.

The objective of this paper is to describe the design of an experiment that will examine the effects of elevated acceleration environments on a high-temperature, titanium-water loop heat pipe for actuator cooling. An experimental test setup has been designed for mounting a loop heat pipe on an 8-ft-diameter centrifuge table, which is capable of radial accelerations of up to 12 g's. A high-temperature PAO loop will interface the condenser of the loop heat pipe to simulate the rejection of the transported heat to an elevated temperature. In addition to LHP experimentation, a mathematical model has been developed for aerodynamic heating of highspeed aircraft. A flat plate at zero-incidence, used to model an aircraft wing, was subjected to sub- and supersonic flow to examine whether heat will be rejected or absorbed. The results of this analysis will be used to determine the condenser conditions of the loop heat pipe during centrifuge testing.

The objective of this paper is to design and fabricate a micro-cooler to provide integral cooling to electronics or Microelectromechanical Systems (MEMS) type components utilizing current MEMS technologies. A three-port capillary pumped loop (CPL) was analyzed and fabricated from silicon and quartz for this purpose. An analytical study of the device is presented in support of this design. This proves the feasibility of such a device, and thus the rationale for continuing its development.

An innovative thermal management system (TMS) that provides both effective active heat transfer and high passive thermal energy storage capacity has been developed and successfully demonstrated. The TMS integrates the high latent heat advantages of a phase change material with an actively cooled cold plate design. The resulting TMS concept has direct use on many transient system applications, where the amount of heat dissipated varies over time. The example discussed in this paper is the transient operation of electric flight control actuator hardware that is proposed for the More Electric Aircraft (MEA) Initiative. The development of the TMS concept, the successful fabrication and validation testing on actual flight control electronic hardware is provided. The advantages of the Thermal Management System include: significant weight savings, high thermal performance, high thermal energy storage capability, high reliability and reduced maintenance.

A two-phase thermosyphon cooler coupled with phase change material (PCM) energy storage was built to demonstrate a concept for cooling a 26 kW actuator motor. FC75®, a Fluorinert® compound, was used as the working fluid to transfer heat to the phase change material, acetamide. The PCM was contained in alternating layers of a plate-fin compact heat exchanger core. At the 90 percent power condition the peak motor temperature was within 90°C of the heat sink, showing good source to sink thermal coupling by the thermosyphon and conductive links. Conversely, when the motor was cooled by natural convection and conduction alone, the peak temperature was 190°C above sink temperature. Testing shows that the PCM material provides additional useful thermal inertia during the melting process. However, test data revealed that the melt temperature of the acetamide had been depressed from 80°C to 68°C by absorbed water, highlighting the need to process the PCM in a dry atmosphere.

This paper reports on the effects of transient transverse and axial acceleration forces with step changes in input power on the performance of a flexible copper/water arterial heat pipe. Transient transverse accelerations were generated using a centrifuge table to simulate acceleration forces typifying high performance aircraft maneuvering. These transients consisted of step changes, steady periodic, and burst cycles in the transverse acceleration forces. Steady periodic and burst cycle transverse accelerations had frequencies of 0.01 and 0.03 Hz with peak-to-peak values of 1.1 to 9.8 g. Partial depriming of the artery, pooling of the unconstrained working fluid, and fluid sloshing were found to have a significant impact on the heat transport potential and transient behavior of the heat pipe. Repriming of the heat pipe under thermal load while being subjected to transient transverse accelerations was also demonstrated.

This paper reports the experimental and analytical investigation on the transient behavior of a heat pipe subjected to a heat load resulting from an actuator duty cycle. A simple analysis is presented which predicts the temperature response to a steady periodic square wave heat load of varying periods. The analytical calculations are compared to experimental results for a heat pipe operating without dry-out.

A review of rotating thermosyphon technology with specific applications in aircraft thermal management and control is given. Successful use and operation of thermal control systems aboard aircraft require high performance operation in environments consisting of high “g” loads, vibration and multiple orientation possibilities. Rotating thermosyphon technologies offer possible applications in aircraft thermal management and control in these operating environments and provide capabilities for dissipating high heat flux thermal loads.