Using a Tray Dryer to Investigate Convective and Conductive Heat Transfer
Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Dryers are utilized in numerous industrial processes. The function of a dryer is to use heat transfer processes to dry solids. A variety of dryer types exist. Adiabatic dryers use convection and direct contact with gases to dry solids, whereas non-adiabatic dryers use methods other than heated gas contact to dry1, including conduction, radiation, and radio frequency drying1. Dryers can be used for batch processes or they be in continuous use1.
In this experiment, the effects of temperature and air velocity on the drying rate of sand will be determined using a tray dryer. Three different power settings (1000 W, 1500 W and 2500 W) for two different air flow rates will be tested, providing a total of six data sets. From this data, the heat and mass transfer coefficients can be calculated.
The experiment will consist of four runs, each testing a different combination of one of two fan and heat settings.
1. Tray Dryer Operation
- Prepare the slurry by mixing 500 g of sand and 150 mL of water and load into the experimental tray for the unit. Spread the mixture evenly in the tray.
- With the main unit off, place the tray in the drying chamber.
- Turn on the main unit, then turn on the blower and heater.
- Set the air velocity and temperature for ea
From the data collected, the following information can be obtained. Use psychrometric charts to determine the absolute humidity, which gives the concentration of water present in the air. The heat transfer coefficients can be calculated using the measured temperatures and Equation 1. And finally, the change in mass of the wet sand can be used to calculate the concentration of water in the sand.
The moisture content of sand decreased linearly over time. As expected, the evaporation rate was fou
A tray dryer was used to measure the drying rate of sand with respect to convective and conductive heat transfer. Using the dryer at three different power levels and two different flow rates, six experimental data sets were found. Measurements were taken by weighing the sand/water mixture at five minute intervals.
This experiment made use of Newton’s Law of Heating, drying rate modeling, and heat and mass transfer modeling. Heat and mass transfer coefficients were determined with the use
- "Solids Drying: Basics and Applications - Chemical Engineering." Chemical Engineering Solids Drying Basics and Applications Comments. N.p., n.d. Web. 12 Jan. 2017.
- "Pharmainfo.net." Tray dryer by Saraswathi.B. N.p., n.d. Web. 12 Jan. 2017.
- "Unit Operations in Food Processing - R. L. Earle." Unit Operations in Food Processing - R. L. Earle. N.p., n.d. Web. 12 Jan. 2017.
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