In this numerical study, heat transfer characteristics and hydrodynamical
analysis have been performed for a circular tube inserted with twisted tape,
which has different twisted pitch ratios (TPR=0, 50, 100, and 200). As a
working fluid Al2O3/water nanofluid is used which has different volumetric
concentrations (0.0≤φ≤3.0 vol. %). The numerical analysis has been carried out
under the constant wall heat flux (q′′) of 4357 W/m2 for laminar flow ranging
the Reynolds (Re) number from 1000 to 2000. According to numerical results,
the highest average Nusselt number (Nu) and average Darcy friction factor (ff)
have realized in twisted pitch ratio (TPR) 50. The reason is that when the
twisted pitch ratio gradually decreases, stronger secondary flows and a higher
velocity can be obtained. When compared with water, the highest Nu for
TPR=50 has been obtained at φ=3.0 vol. % concentration as 61.15%. Also,
when compared with TPR=0, the highest thermal performance enhancement
(TPE) was realized at φ=3.0 vol. % concentration and Re=2000 conditions as
61.15% for TPR=50.
Keywords:
CFD
Convective heat transfer
Laminar flow
Al2O3/water
Twisted tape
This study was performed to define the kinetic drying model and to define the effective diffusivity coefficient of the fruit, which is called ottoman strawberries in the literature. In the study, strawberries by the weight of 100 g and with a thickness of 5 mm were placed in the drying device, and the data were processed by observing the weight loss every two hours after being subjected to the drying process for 14 hours. 8 different kinetic drying models were applied to the acquired data using the MATLAB program. As a result of the application, the estimated standard errors (RMSE), chi-square (X2), regression coefficients (R2) were calculated, error analysis was performed, R2, X2, and RMSE values were found, as 9,998×10-1, 6,993×10-5 and 0.7242×10-2. According to these results, it was determined that the most suitable model is the Page model. Also, the effective diffusivity coefficients for ottoman strawberries were calculated as 2.73286 × 10-10 m2/s. It was confirmed that the calculated effective diffusivity value was within the reference range mentioned in the literature (10-12 m2/s – 10-8 m2/s) for food products.
Investigation of Freeze-Drying characteristic of kiwi slices with various thicknesses. The proper kinetic drying model was specified by using MATLAB software. The effective diffusivity (Deff) values were computed by drawing drying value.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.