The problem of laminar combined free and forced convection through vertical noncircular ducts and passages in the fully developed region has been treated. The fluid properties are considered to be constant, except the variation of the density in the buoyancy term of the momentum equation. Pressure work and viscous dissipation terms of the energy equation have been neglected. Heat flux has been considered to be constant in the flow direction. A general solution to the problem has been obtained in "the form of infinite series containing modified Bessel functions. Two possible thermal boundary conditions on the circumference of the heated wall have been analyzed, Case 1 - uniform circumferential wall temperature, and Case 2 - uniform circumferential wall heat flux. Information of engineering interest like Nusselt number, heat flux, ratio, shear stress ratio, temperature distribution on the' wall, velocity and temperature distributions in the flow field have been obtained for two sets of geometries, namely, (i) flow through regular polygonal ducts, and (ii) flow between cylinders arranged in regular arrays. For flow through regular polygonal ducts, the case of uniform circumferential wall temperature results in higher values of Nusselt numbers as compared to the case of uniform circumferential wall heat flux. This difference in Nusselt number values decreases as the number of sides of the regular polygon is increased, until for a circle it completely disappears. For both the cases, at higher values of Rayleigh number, the Nusselt number is less sensitive to the number of sides of the polygon. Also, at higher values of Rayleigh number, both the cases tend to produce the same results. For low sided polygons, an increase in Rayleigh number tends to shift the maximum value of shear stress from the centre of the duct wall towards the apex of the duct. For flow between cylinders arranged in regular arrays, Case 1 results in higher values of Nusselt number compared to Case 2, for low spacing ratios. However, as the spacing ratio is increased, the two cases tend to produce the same results. Cylinders arranged in equilateral triangular arrays produce higher values of Nusselt number compared to those in square arrays. This difference in Nusselt number values decreases when the spacing ratio is high. For higher values of Rayleigh number, however, the results are less sensitive to the type of arrays. Also, at higher values of Rayleigh number, both the cases tend to produce the same results. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Analysis of combined free and forced convection through vertical non-circular ducts has been carried out using variational technique. Fully developed flow with uniform axial heat input is assumed. All fluid properties are considered invariant with temperature except the variation of density in the buoyancy term of the equation of motion. A general study of the problem has been made in three stages: (i) Forced convection without circumferential wall conduction. For this case, a known velocity expression is used and a particularly simple variational expression has been presented. Nusselt numbers are calculated for rectangular, rhombic, isosceles triangular, and right-angled triangular ducts. Results compared with the available solutions have shown excellent agreement. (ii) Combined free and forced convection without circumferential wall conduction. Nusselt numbers have been computed for rectangular and rhombic ducts. A finite-difference procedure has also been carried out and the results are presented for rhombic duct only. In both of the above cases (i) and (ii), the condition of uniform peripheral heat flux has been directly utilized in deriving the variational expression, thus releasing the thermal boundary condition from satisfying exactly the condition at the wall. The condition of uniform circumferential heat flux results in lower values of Nusselt numbers as compared to that of uniform circumferential wall temperature. This difference in Nusselt number values decreases with the increase in Rayleigh number. At higher values of Rayleigh number, both the conditions tend to produce about the same results. (iii) Conjugate problem of combined free and forced convection when peripheral wall conduction is included. The equations coupling heat conduction in the walls with the convection inside the fluid are solved to establish the influence of peripheral wall conduction. The problem has been solved in a generalized way and the results have been presented for rectangular ducts. It is found that large values of the free convection effects and/or of the conduction parameter tend to minimize the asymmetries in circumferential wall temperature. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The study of two phase flow, where a finely divided solid is suspended in a fluid medium, has received considerable attention in the last five years due to the increased number of systems in which this phenomena occurs. The two most important areas involving the gas- particle mechanism are nuclear reactor heat exchangers and liquid and solid rockets.

A gap of knowledge lies within the hazard of extreme heat within the United States and the public’s response and perception of their own vulnerability. Even with constant communication from meteorologist at the National Weather Service and within the broadcast industry, there are still ongoing issues which include the possibility that ambient air temperature from fixed sites do not accurately reflect what the general population is experiencing, that the thresholds for excessive heat warnings are not appropriate, and that the most vulnerable individuals do not have the knowledge, and/or ability to protect themselves when extreme heat does occur. Assessment of the spatial pattens of heat alerts across the United States, mortality risks associated with extreme heat, and days above alert thresholds between 2010 to 2021 will be utilized to exhibit cities and regions where thresholds could be inappropriate and to reveal the most vulnerable between regions within this period.

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Several types of research are ongoing throughout the world, to discover economical and reliable techniques to create hydrogen, and propagate the vision of a hydrogen economy. This research examines a COMSOL Multiphysics 5.4 heat transfer model for a hydrogen production system consisting of a retort with two different heat sources, namely a heat tape and an infrared (IR) lamp. The main objective was to compare the two heat sources and find out which one offers a better technique for producing hydrogen by raising the internal center core temperature of the retort from ambient to the highest temperature, preferably 700℃, within the shortest time possible and using less power consumption in attaining the targeted temperature. Through this study, it was established that the IR lamp could potentially help with energy savings by using just 4 kWh to reach the targeted temperature within an hour.