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A study was conducted to examine the natural convection fluid structure and heat transport between two horizontal, differentially heated circular cylinders in an adiabatic circular enclosure. The study considers the impact of gap width between cylinders and the enclosure's inclination angle. It is shown that the Rayleigh number, inclination angle and gap width influence fluid flow and heat transfer.

Numerical simulation is used to analyze the perturbing effect of the axial rotation of the inner cylinder on the bouyancy-driven convection of cold water in a vertical cylindrical annulus with density inversion effects. Results showed that mixed convection and fluid flow is affected by the density inversion effects. The centrifugally forced convection can also increase the bouyant convection heat transfer for the density parameters 0.4 or 0.5. Axial rotation of the inner cylinder is therefore an effective way of increasing the natural convection heat transfer of cold water.

The major objective of engineering change is to redesign product/component parts to perform better or to be produced more efficiently. However, frequent engineering changes contribute to scheduling instability. When a material requirements planning (MRP) system is used as the production planning and inventory control method, scheduling instability becomes the most difficult problem for production planners to deal with. The purpose of this paper is to evaluate the trade-off between frequent engineering changes and resultant cost increments in writing off obsolete items. A simulation experiment is conducted to examine the effect of different frequencies of engineering changes on the performance of a multi-level MR P system under various operating environments. An analysis is also performed to evaluate the sensitivity of base experimental results to changes in important parameters which are held constant in the simulation experiment. Results show that frequent engineering changes indeed deteriorate MR P system performance considerably. Furthermore, an appropriate selection of a lot-sizing rule tends to mitigate the impact of frequent engineering changes. A lot-sizing rule such as part-period balancing consistently generates the least cost increment as engineering changes become frequent. [ABSTRACT FROM AUTHOR]

In the present study, experimental efforts have been performed to explore the forced convection heat transfer using water-based suspension of Al 2 O 3 nanoparticles (nanofluid) to replace the pure water as the working fluids in circular tubes. The nanofluid was prepared as a functional forced convection fluid and the thermal properties including the density, thermal conductivity, and dynamic viscosity were investigated experimentally. Besides, forced convection heat transfer in circular tubes was investigated with water-based nanofluid containing various mass fractions of the Al 2 O 3 nanoparticles (2, 5, and 10 wt%) under the following operating conditions: the volume flow rate Q f = 23.6–183.5 cm 3 /min (the Reynolds number Re f ,0 = 188–2095), the heating power applied at the outer wall of the tube q o , eff . ″ = 1908–7362 W/m 2 , and the inlet fluid temperature T in = 24.5–25.5 °C or 49.5–50.5 °C. Measured data showed that the dispersion of increasing mass fraction of Al 2 O 3 nanoparticles can effectively improve the thermal conductivity relative to the pure water. Besides, higher average heat transfer effectiveness ε − h , btd and figure of merit FOM are noted for the cases with higher inlet fluid temperature T in . [ABSTRACT FROM AUTHOR]