91C-21 |
An interactive-visual computer generated psychrometric chart |
F. ERDOGDU, Food Engineering Department, Mersin University, Ciftlikkoy-Mersin, 33342, Turkey and R. P. Singh, Biological and Agricultural Engineering, University of California, Davis, Bainer Hall, Davis, CA 95616. The determination of thermal and physical properties of air-water mixtures (psychrometrics) is important in food and agricultural engineering problems, e.g., control of temperature and relative humidity; drying, evaporation and transpiration problems. The availability and afford-ability of PCs have made the numerical and visual graphical calculations for engineering problems easier, and this can be also used to generate an interactive psycrometrics chart for any specific range of interest. The objectives of this study were to develop a computer generated psychrometric chart within a specified range, make the determination of different properties easier and let the users play what-if games visually on the interactive chart to gain a better understanding of different processes. The computer program was written in Visual Basic V.6.0 to generate the interactive chart and determine the psyhrometric properties (dry bulb and wet bulb temperatures, relative humidity, humidity ratio, enthalpy, dew point, humid heat, specific volume) of moist air using equations listed in ASAE D271.2 at different atmospheric pressures. A graphical interface (Pinnacle Graphic Server V.5.5) was also used in the program to give the user an easier and better interactive visual representation. The calculations were tested in a wide range of conditions, and the average percentage error was found to be less then 5%. This program easily generated the psychrometric chart within any specified temperature range and pressure and made all the calculations visually letting the users see how any change in one property will affect the all others. On the interactive graph, all the properties can be determined with a move of mouse and seen on the screen. This program made the psychrometrics-related calculations and graphical readings easier and faster, and a psychrometric chart in a specified range can be easily formed with the extensive interactive visual graphical abilities of the program.
Session 91C, Food Engineering: Food process engineering
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