Maximum heat transfer density rate enhancement from cylinders rotating in natural convection

Abstract

In this paper we investigate the thermal behaviour of an assembly of consecutive cylinders in a counter-rotating configuration cooled by natural convection with the objective of maximizing the heat transfer density rate (heat transfer rate per unit volume). A numerical model is used to solve the governing equations that describe the temperature and flow fields. The spacing between the consecutive cylinders is optimised for each flow regime (Rayleigh number) and cylinder rotation speed. It was found that the optimized spacing decreases as the Rayleigh number increases and the heat transfer density rate increases, for the optimized structure, as the cylinder rotation speed is increased. Results further shows that there is an increase in the heat transfer density rate of the rotating cylinders over stationary cylinders.

Constructal multi scale cylinders with rotation cooled by natural convection

“…The results for a single row of heat-generating rotating cylinders in natural convection was presented previously by Page et al [29]. This paper focuses on taking the constructal design of optimal spacings in a new direction by numerically formulating the problem and mathematically optimising the flow configuration.…”

“…It is interesting to note that, at a cylinder rotation speed of ω 0 = 10, the maximum heat transfer density rate is suppressed for all Rayleigh numbers in the range 10 2 ≤ Ra ≤ 10 4 . Figure 11 shows a comparison between the multi scale and single scale [29] configurations for the optimal cylinder-to-cylinder spacing. The multi scale configuration has the effect of increases the optimal cylinder-to-cylinder when adding a smaller diameter cylinder in the mouth of the channel.…”

“…The maximum cylinder packing, from a physical point of view, is obtained using a single scale configuration with rotation. Figure 12 shows a comparison between the multi scale and single scale [29] configurations for the maximum heat transfer density rate. Although the effect of cylinder rotation (on a single scale configuration) is an increase in the maximum heat transfer density rate, a multi scale configuration (without any cylinder rotation) achieves a higher maximum heat transfer density rate.…”

Passive Drag Reduction Techniques for Modulating the Effects of Vortex Shedding

“…Optimum rates of rotation were reported at a specific Reynolds number and insight was given as to the mechanism by which vortex shedding is modulated. A number of other researchers also investigated the effect of rotary motion on natural convection heat transfer [11] and the effect of Prandtl number on the process [12]. The idea of introducing a rotary oscillation component to the motion of the cylinder was introduced as early as the early nineties, as experimentally reported by Tokumaru and Dimotakis [13] and then numerically investigated by Baek and Sung [14].…”

Constructal optimisation of conjugate triangular cooling channels with internal heat generation

“…In this analysis, it was shown that through the use of interstitial microtubes, the maximum heat transfer rate density for an array of circular tubes increased. Page et al [22], numerically, investigated the thermal behaviour of an assembly of consecutive heat generating cylinders in stationary, rotating and counter-rotating configurations cooled by natural convection with the objective of maximizing the heat transfer density rate by optimising spacing between the consecutive cylinders. Reis et al [23] optimised the internal configurations of parallel plates and cylindrical channels using contructal theory to understand the morphology of particle agglomeration and the design of air-cleaning devices.…”