73C-23 |
Use of ablation to determine the convective heat transfer coefficient in two-phase flow |
W. A. TESSNEER1, B. E. Farkas, and K. P. Sandeep. (1) Department of Food Science, North Carolina State University, 129 Schaub Hall, Box 7624, Raleigh, NC 27695 Detailed knowledge of the convective heat transfer coefficient (h) is critical for successful application of aseptic processing to low acid liquid foods with particulates. Determination of h is difficult, as it is dependent on information such as fluid temperature, fluid properties, and relative velocity of the fluid over the particle. The objectives of this research were to 1) Develop a new method for determination of the convective heat transfer coefficient using ablation heat transfer, 2) Determine the convective heat transfer coefficient over a range of Reynolds numbers using the new method, and 3) Examine limitations of the new method and how it compares with previously developed techniques. The convective heat transfer coefficient was determined using a new method based on ablation heat transfer. The amount of solid lost (ablated) was shown to be directly proportional to the energy flux across the fluid-solid interface with the constant of proportionality being h. Change in mass of an ice sphere was used as an ablation probe to study h in straight, round conduit. Values of h ranged from 1369 to 2749 W/m^2K over a Reynolds number range of 2,766 to 17,081. Heat transfer coefficients increased with increasing Reynolds numbers. Advantages to this new method include low cost and the ability of the particle to move freely within the system during testing. The application of this method could have a significant influence on the implementation of an aseptic process of liquids containing particulates. This method was found to be reproducible and the results fall within the range of values obtained from previous studies.
Session 73C, Food Engineering: Transport Processes and Kinetics
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