Curtt N. Ammerman Proposed Statement of Research
Curtt N. Ammerman
University of Texas at Arlington

Introduction.My current research is in the area of boiling heat transfer and two-phase flow. Boiling heat transfer is being considered for many space-related applications such as thermal management on board spacecraft (Fairuzov and Bredikhin, 1995). Compared to single-phase cooling schemes, boiling allows more waste heat removal per unit of flow because latent heats of vaporization are much greater than heat capacities of various liquids. In addition, boiling allows for nearly isothermal heat transfer conditions which are desirable for electronics cooling. Boiling is also being considered for power generation using dish-type solar receivers combined with Stirling engines (Cameron, 1993) and space-based nuclear reactors.

Previous Research. I am studying the mechanisms of enhancement in both pool- and flow boiling heat transfer. There are considered to be four heat removal mechanisms in pool boiling: natural convection, latent heat, microconvection, and Marangoni flow. In the course of my research, I have developed a photographic/laser Doppler anemometry measurement technique (named the Single-Photo Method) for quantifying the different heat transfer mechanisms that result when boiling occurs from a small heated cylinder immersed in a saturated liquid (Ammerman et al., 1996). I have applied this technique to aid in the understanding of boiling enhancement which takes place when surfactants are added to water (Ammerman and You, 1996). Understanding which heat transfer mechanisms are affected by a given enhancement method will enable optimization of future heat exchanger designs. Such optimum designs are vital for space-based applications allowing for minimum system weight.

Proposed Research. My goal is to determine the mechanisms of enhancement for both pool and flow boiling with microporous coatings. I am proposing a two-step plan to achieve this goal. 1) I plan to apply the Single-Photo Method to determine boiling mechanisms from a small cylinder with a microporous surface coating. To my knowledge, this will be the first time that heat transfer mechanisms have been quantified for a porous surface. 2) I plan to design, build, and test a mini channel heat sink under flow boiling conditions-with and without a microporous coating. In addition, I plan on visualizing the flow in the mini-channel in the hopes of obtaining heat transfer mechanism information. By combining the results from this test with the test in Step (1), I hope to make an assessment of the flow boiling heat transfer mechanisms for a microporous coating.

References

Ammerman, C.N., Hong, Y.S., and You, S.M., 1996, "Identification of Pool Boiling Heat Transfer Mechanisms From a Wire Immersed in Saturated FC-72 Using a Single Photo/LDA Method," ASME Journal of Heat Transfer, Vol. 118, p. l l7.

Ammerman, C.N. and You, S.M., 1996, "Determination of the Boiling Enhancement Mechanism Caused by Surfactant Addition to Water," ASME Journal of Heat Transfer, Vol. 118, p.429.

Cameron, C.P., 1993, "High Heat Flux Engineering in Solar Energy Applications," SPIE Vol. 1997 High Heat Flux Engineering 11, p. 460.

Fairuzov, Y.V. and Bredikhin, V.V., 1995, "Two-Phase Cooling System with a Jet Pump for Spacecraft," Journal of Thermophysics and Heat Transfer, Vol. 9, No. 2, p. 285.



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