Three-dimensional multi-scale plate assembly for maximum heat transfer rate density

International Communications in Heat and Mass Transfer

Bello‐Ochende

Meyer

2011

Self Cite

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.

Section: Introductionmentioning

confidence: 99%

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

International Communications in Heat and Mass Transfer

Bello‐Ochende

Meyer

2011

Self Cite

“…The results report in this literature confirmed the results, derived analytically by Bejan et al [18], for the same problem. A three dimensional parallel plate multi scale structure cooled by laminar natural convection was also considered, more recently, by Bello-Ochende et al [19].…”

Section: Increased Geometric Complexitymentioning

confidence: 99%

Geometric Optimization for Maximum Heat Transfer Density Rate From Cylinders Rotating in Natural Convection

Proceeding of Proceedings of CHT-12. ICHMT International Symposium on Advances in Computational Heat Transfer.

2012

Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a i Abstract Title: Geometric optimization for the maximum heat transfer density rate from cylinders rotating in natural convection Author:LG Page Supervisors: Prof T Bello-Ochende and Prof JP Meyer Department: Mechanical and Aeronautical Engineering University:University of Pretoria Degree:Masters in Engineering (Mechanical Engineering)In this study we investigates 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 was used to solve the governing equations that describe the temperature and flow fields and an optimisation algorithm was used to find the optimal structure for flow configurations with two or more degrees of freedom. The geometric structure of the consecutive cylinders was optimized for each flow regime (Rayleigh number) and cylinder rotation speed for one and two degrees of freedom. Smaller cylinders were placed at the entrance to the assembly, in the wedge-shaped flow regions occupied by fluid that had not yet been used for heat transfer, to create additional length scales to the flow configuration.It was found that the optimized spacing decreases and the heat transfer density rate increases as the Rayleigh number increases, for the optimized structure. It was also found that the optimized spacing decreases and the maximum heat transfer density rate increases, as the cylinder rotation speed was increased for the single scale configuration at each Rayleigh number. Results further showed that there was an increase in the heat transfer density rate of the rotating cylinders over stationary cylinders for a single scale configuration.For a multi scale configuration it was found that there was almost no effect of cylinder rotation on the maximum heat transfer density rate, when compared to stationary cylinders, at each Rayleigh number; with the exception of high cylinder rotation speeds, which serve to suppress the heat transfer density rate. It was, however, found that the optimized spacing decreases as the cylinder rotation speed was increased at each Page iii Rayleigh number. Results further showed that the maximum heat transfer density rate for a multi scale configuration (with stationary cylinders) was higher than a single scale configuration (with rotating cylinders) with an exception at very low Rayleigh numbers.

“…This has lead researchers to study the optimized configurations for various architectures such as: the optimal spacing of parallel plates in forced convection, natural convection and mixed convection [7,8,10,35]; the optimal spacing of cylinders in forced convection and natural convection [36,37]; and various optimized multi-scale structures [4,9,[11][12][13]34], etc.…”

Section: Introductionmentioning

confidence: 99%

Constructal multi scale cylinders with rotation cooled by natural convection

International Journal of Heat and Mass Transfer

Bello‐Ochende

Meyer

2013

Self Cite

In this paper we investigated the thermal behaviour of an assembly of multi scale cylinders in a staggered counterrotating configuration cooled by natural convection with the objective of maximizing the heat transfer density rate (heat transfer rate per unit volume). A numerical model was used to solve the governing equations that describe the temperature and flow fields and a mathematical optimisation algorithm was used to find the optimal structure for flow configurations with two degrees of freedom. The multi scale structure of the cylinder assembly was optimized for each flow regime (Rayleigh number) and cylinder rotation speed for two degrees of freedom. Smaller cylinders were placed at the entrance to the assembly, in the wedge-shaped flow regions occupied by fluid that had not yet been used for heat transfer, to create additional length scales to the flow configuration.It was found that there was almost no effect of cylinder rotation on the maximum heat transfer density rate, when compared to stationary cylinders, at each Rayleigh number; with the exception of high cylinder rotation speeds, which served to suppress the heat transfer density rate. It was, however, found that the optimized spacing decreased as the cylinder rotation speed was increased at each Rayleigh number. Results further show that the maximum heat transfer density rate for a multi scale configuration (without cylinder rotation) was higher than a single scale configuration (with rotating cylinders) with an exception at very low Rayleigh numbers.