Jeremy Rice

Thermal and Start-Up Characteristics of a Miniature Passive Liquid Feed DMFC System, Including Continuous/Discontinuous Phase Limitations

The thermal and start-up characteristics of a passive direct methanol fuel cell system are simulated using a numerical model. The model captures both the thermal characteristics of the fuel cell and the passive fuel delivery system using a multifluid model approach. Since the fuel cell is run without any active temperature control, the temperature may rise until the convective and evaporative cooling effects balance the heat produced in the chemical reactions. The cell temperature can vary as much as 20°C, and it is vital to model the thermal effects for accurate results. The numerical model also includes continuous and discontinuous phase limitations, as well as a probabilistic spread of the porous properties. These added physical characteristics qualitatively portray the departure of carbon dioxide from the anode side of the fuel cell.

Analysis of screen wick heat pipes, including capillary dry-out limitations

A complete numerical analysis of heat pipes is performed with no empirical correlations while including the flow in a wick. The numerical model is validated from experimental and numerical work. Single and multiple heat sources were used as well as constant, convective, and radiative heat sinks. The numerical model does not fix the internal pressure references by a point, but allows it to rise and fall based on the physics of the problem. Also, the capillary pressure needed in the wick to drive the flow is obtained for various heating configurations and powers. These capillary pressures, in conjunction with an analysis that predicts the maximum capillary pressure for a given heating load, are used to determine the dry-out limitations of a heat pipe.

A New Computational Method to Track a Liquid/Vapor Interface With Mass Transfer, Demonstrated on the Concentration Driven Evaporation From a Capillary Tube, and the Marangoni Effect

A new computational liquid/vapor interface tracking technique is developed to model an interface between a liquid and a vapor including mass transfer. This technique does not require the use of an additional transport equation, as does the VOF method, while still being implemented without a complicated solution procedure. This new interface tracking technique is used to capture the liquid/vapor interface in a capillary tube of 100 μm scale. The diffusion driven evaporation process is studied, along with the Marangoni convection that is caused by the temperature gradient along the interface. The results are qualitatively and quantitatively compared to existing experimental data.Copyright

Analysis of the Marangoni Effect in Volatile Liquids Evaporating from Capillary Tubes Using a New Interface Tracking Method

A new computational liquid/vapor interface tracking technique is developed to model an interface between a liquid and a vapor including mass transfer. This technique does not require the use of an additional transport equation, as does the volume-of-fluid (VOF) method, while still being implemented without a complicated solution procedure. This new interface tracking technique is used to capture the liquid/vapor interface in a capillary tube of 100-μm scale. The diffusion-driven evaporation process is studied, along with the Marangoni convection that is caused by the temperature gradient along the interface. The results are qualitatively and quantitatively compared to existing experimental data.

A New Computational Method for Free Surface Problems

A new technique, called the surface velocity correction (SVC) technique, is developed to track a free surface such as a liquid–vapor interface. The SVC is a computationally inexpensive and accurate method to capture interfacial fluid phenomena. This method uses a finite-volume technique to discretize the governing equations, and a semi-Legrangian mesh to locate the interface between two fluids. The effectiveness of this technique is demonstrated through several classical examples and the results are also compared to both analytical and volume-of-fluid (VOF) solutions. The examples include the shape of a meniscus in a capillary tube in mechanical equilibrium, the rise of a meniscus in a capillary tube, and the instability growth of a free-flowing cylindrical column of fluid.

Analysis of a Free Surface Film from a Controlled Liquid Impinging Jet over a Rotating Disk Including Conjugate Effects, with and without Evaporation

A detailed analysis of the liquid film characteristics and the accompanying heat transfer of a free surface controlled liquid impinging jet onto a rotating disk are presented. The computations were run on a two-dimensional axi-symmetric Eulerian mesh while the free surface was calculated with the volume of fluid method. Flow rates between 3 and 15 Ipm with rotational speeds between 50 and 200 rpm are analyzed. The effects of inlet temperature on the film thickness and heat transfer are characterized as well as evaporative effects. The conjugate heating effect is modeled, and was found to effect the heat transfer results the most at both the inner and outer edges of the heated surface. The heat transfer was enhanced with both increasing flow rate and increasing rotational speeds. When evaporative effects were modeled, the evaporation was found to increase the heat transfer at the lower flow rates the most because of a M y developed thermal field that was achieved. The evaporative effects did not significantly enhance the heat transfer at the higher flow rates.

Analysis of Porous Wick Heat Pipes, Including Capillary Dry-Out Limitations

A complete numerical analysis of heat pipes is performed with no empirical correlations while including the flow in a wick. The numerical model is validated from experimental and numerical work. Single and multiple heat sources were used as well as constant, convective and radiative heat sinks. The numerical model does not fix the internal pressure references by a point, but allows is to rise and fall based on the physics of the problem. Also, the capillary pressure needed in the wick to drive the flow is obtained for various heating configurations and powers. These capillary pressures, in conjunction with an analysis that predicts the maximum capillary pressure for a given heating load is used to determine the dry-out limitations of a heat pipe.Copyright