The model is based on the conservation equations of mass, momentum and energy. The following figure illustrates some of the results.
(To view a larger image of the following infrared camera output images, simply click on the image.) Flow is from the left to the right. The heaters are attached to the top of the test article (i.e. the images are upside down. Physical constraints on the camera forced us to put it upside down.) The vertical marks are approximately 1 inch apart. All temperatures are in degree Celsius with the corresponding color to temperature scale located at the top of each image.
Note: the first two images have the same input values but the first image is of single-phase heat transfer only.
Single-phase heat tranfer, lead spheres Heat flux q"=3.3 W/cm^2, pore velocity of the liquid = 1.5 cm/s
Two-phase heat transfer, lead spheres Heat flux q"=3.3 W/cm^2, pore velocity of the liquid = 1.5 cm/s
Two-phase heat transfer, copper filings Heat flux q"=4.15 W/cm^2, pore velocity of the liquid = 1.5 cm/s
Comparison Of The Model With Test Results
The model was developed to determine the liquid-vapor interface location. This profile may then be used to calculate the surface temperature or any other thermophysical behavior of interest.
As is apparent from the figures, very good agreement between the model and experimental data has been obtained.
We note in all cases of two-phase heat that a very uniform surface temperature is attained. This situation is ideal for applications involving electronic components such as computer chips which not only require high heat flux dissipation but also very small temperature gradients to reduce thermal stress. The following model prediction has an applied heat flux of 100 W/cm^2 with water as the working fluid. The channel height is 1mm. The blue and white lines represent surface temperatures if the working fluids were water and water vapor, respectively. The red line represents the surface temperature if phase change were to occur. Note: the surface temperature increases by only 15.5 degrees Celcius with most of the increase occurring within the first 25% of the two-phase zone.
Dr. Todd Dickey, james.t.dickey@aero.org, is an employee of The Aerospace Corporation, in El Segundo, CA. This research was conducted as part of his Ph.D. work. Todd is a Licensed Professional Engineer who, after completing his B.S. in Mechanical Engineering at Purdue University, worked in industry for 3 years before attending Texas A&M University to earn his M.S. and Ph.D. degrees in Mechanical Engineering. Follow the link to view his resume.
