Browsing by Subject "centrifuge"
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Item Centrifuge testing of an expansive clay(2009-08) Plaisted, Michael D.; Zornberg, Jorge G.; Gilbert, Robert B.Expansive clays are located world wide and cause billions of dollars in damage each year. Currently, the expansion is usually estimated using correlations instead of direct testing as direct testing is expensive and often takes over a month to complete. The purpose of this study was to determine if centrifuge technology could be used to characterize expansive clays through direct testing. Testing was performed in an centrifuge permeameter on compacted specimens of Eagle Ford clay. A framework was developed to analyze effective stresses in centrifuge samples and methods were proposed to determine the swell-stress curve of a soil from centrifuge tests. Standard free swell test were also performed for comparison. The swell-stress curve determined by centrifuge testing was found to match with the curve found from free swell tests after correcting for differences in testing procedures. The centrifuge tests were found to be repeatable and required several days for testing rather than weeks.Item Design and Optimization of Condenser and Centrifuge Units for Enhancement of a Batch Vacuum Frying System(2011-02-22) Pandey, AkhileshA batch vacuum frying system, which processes fruits and vegetables, includes a frying pan, a surface-condenser, and a vacuum pump. With health and safety issues in mind, this research focused on developing a modified surface-condenser to prevent cavitation of the vacuum pump. The final oil-content was reduced by centrifugal de- oiling of the product under vacuum, which make the product healthier than what is currently available. The de-oiling mechanism consists of a centrifuge with a motor attached to the basket shaft, rotating up to 750 rpm (63 g units). The condenser consists of a (counter- flow) spiral-coil heat exchanger (SHE) connected to a refrigeration system that uses R404a refrigerant. De-oiling for 40 s at 300 and 750 RPM removed up to 67% and 72% of the chip?s surface oil, respectively. At 750 RPM for 10 s, 40 s, and 60 s the oil-content was reduced by 38%, 44%, and 51%, respectively. The convective heat transfer coefficient (h) of the frying oil was determined at 120?C and 140?C using the lumped capacitance method. The h-values were 217?13 W/m2K (120?C) and 258?37 W/m2K (140?C) using a copper-ball thermocouple. The h- values increased to 3.6 times during the boiling period. COMSOLTM Multiphysics was used to model the heat transfer in the vacuum fryer pan. Based on the simulation results, a 1.5 cm thick insulation material was installed in the fryer to reduce the energy losses. The refrigeration system operates at Tevap = -26?C and Tcond = 50?C with 26?C sub-cooling. Sensitivity analysis showed that the system Coefficient of Performance (COP) was about 3.87 at these conditions and compressor power requirement (CPR) was 74 W (85% efficiency) when frying 30 g of potatoes slices. The best results were obtained at Tevap = -10?C and Tcond = 40?C with 26?C sub-cooling and superheat of 5?C. The predicted COP was 4 and the CPR 70 W. The ice-formation on coils reduced the condensation rate. Reducing the refrigerant temperature to -10?C (from -26?C) reduced the condensation rate by 30%. These results show a more effective vacuum frying system for high-quality fruits and vegetables than the system previously used.