6 Multi-objective Performance Optimization of a Ribbed Solar …
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transferring surface on heat transfer enhancement have been studied using Taguchi
Method (Bilen et al. 2001). The most significant parameter influencing heat transfer
is the Reynolds number, which is followed by the turning angle of the block. It was
also reported that the heat transfer rate increases with increasing Reynolds number
and turning angle of the block. The cooling effectiveness of a reactor with/without
noise sinking shield was studied by Wang et al. (2009) for avoiding the overheating problem using a systematic CFD-Taguchi approach. The radius of the bottom
and the top opening of noise reducing cover are found to be the most significant
with contribution ratios of 49.5% and 23%, respectively, to the natural convection
cooling performance. The performance of a ribbed SAH was studied by Aghaie
et al. (Aghaie et al. 2015) using CFD-Taguchi approach at a Reynolds number of
10000. The authors optimized a general rib geometry, which can produce triangular,
trapezoidal and rectangular geometries by varying its parameters, while considering
maximization of thermal performance as the criteria of optimization. It was found
that relative rib pitch and height have the greatest influence on performance improvement. Triangular rib geometry was found to be the optimum configuration. Chamoli
(Chamoli 2015) optimized different design parameters, i.e. Reynolds number (Re),
open perforation ratio (β), relative baffle height (e/H) and relative baffle pitch (p/e), of
a rectangular duct roughened with perforated V-down baffle. Maximum heat transfer
and minimum friction factor conditions were found at p/e = 2, e/H = 0.4, β = 12%,
Re = 18600 and p/e = 4, e/H = 0.285, β = 44%, Re = 14800 respectively. Caliskan
et al. (2016) studied the impact of design parameters on heat transfer distribution
for a surface attached with V-shaped and convergent-divergent shaped ribs. Results
revealed that Reynolds number was the most dominant factor influencing heat transfer, and the highest thermal performance was obtained for V-shaped ribs at Reynolds
number of 10000. The aerothermal features of a cross flow heat exchanger with
pin-fins have been studied by Kotcioglu et al. (2018) using Taguchi method with L 25
orthogonal array. The best thermal performance was observed for hexagonal pin-fins,
followed by square-angle pin-fins. Recently, the design parameters, i.e. corner angle,
inclination angle, baffle height, baffle length, baffle width and Reynolds number, of
a heat sink fixed with hollow trapezoidal baffles have been optimized to enhance the
performance (Sahin et al. 2019). The length of the baffle is the greatest influencing factor, with contribution ratio of 32.5%, on the pumping power and Reynolds
number, with influence ratio of 80%, for heat transfer.
The above discussed studies reveal that the rib design parameters i.e. shape, size,
spacing, inline or staggered arrangement, number of ribbed walls, perforation, rib
inclination, and Reynolds number, have significant impact on the overall performance of the heat exchanger mounted with ribs. It has also been reported that the
CFD-Taguchi scheme can be employed easily and also economically for a reliable and robust optimization (Wang et al. 2009; Aghaie et al. 2015). Therefore, the
present research work is primarily concentrated on the prediction of best rib design
parameters for a ribbed SAH using Taguchi method. The ribs have been provided
on the bottom surface, which was exposed to constant heat flux. Firstly, the profound impacts of design parameters, i.e. rib geometry (see Fig. 6.1), rib spacing and
79
transferring surface on heat transfer enhancement have been studied using Taguchi
Method (Bilen et al. 2001). The most significant parameter influencing heat transfer
is the Reynolds number, which is followed by the turning angle of the block. It was
also reported that the heat transfer rate increases with increasing Reynolds number
and turning angle of the block. The cooling effectiveness of a reactor with/without
noise sinking shield was studied by Wang et al. (2009) for avoiding the overheating problem using a systematic CFD-Taguchi approach. The radius of the bottom
and the top opening of noise reducing cover are found to be the most significant
with contribution ratios of 49.5% and 23%, respectively, to the natural convection
cooling performance. The performance of a ribbed SAH was studied by Aghaie
et al. (Aghaie et al. 2015) using CFD-Taguchi approach at a Reynolds number of
10000. The authors optimized a general rib geometry, which can produce triangular,
trapezoidal and rectangular geometries by varying its parameters, while considering
maximization of thermal performance as the criteria of optimization. It was found
that relative rib pitch and height have the greatest influence on performance improvement. Triangular rib geometry was found to be the optimum configuration. Chamoli
(Chamoli 2015) optimized different design parameters, i.e. Reynolds number (Re),
open perforation ratio (β), relative baffle height (e/H) and relative baffle pitch (p/e), of
a rectangular duct roughened with perforated V-down baffle. Maximum heat transfer
and minimum friction factor conditions were found at p/e = 2, e/H = 0.4, β = 12%,
Re = 18600 and p/e = 4, e/H = 0.285, β = 44%, Re = 14800 respectively. Caliskan
et al. (2016) studied the impact of design parameters on heat transfer distribution
for a surface attached with V-shaped and convergent-divergent shaped ribs. Results
revealed that Reynolds number was the most dominant factor influencing heat transfer, and the highest thermal performance was obtained for V-shaped ribs at Reynolds
number of 10000. The aerothermal features of a cross flow heat exchanger with
pin-fins have been studied by Kotcioglu et al. (2018) using Taguchi method with L 25
orthogonal array. The best thermal performance was observed for hexagonal pin-fins,
followed by square-angle pin-fins. Recently, the design parameters, i.e. corner angle,
inclination angle, baffle height, baffle length, baffle width and Reynolds number, of
a heat sink fixed with hollow trapezoidal baffles have been optimized to enhance the
performance (Sahin et al. 2019). The length of the baffle is the greatest influencing factor, with contribution ratio of 32.5%, on the pumping power and Reynolds
number, with influence ratio of 80%, for heat transfer.
The above discussed studies reveal that the rib design parameters i.e. shape, size,
spacing, inline or staggered arrangement, number of ribbed walls, perforation, rib
inclination, and Reynolds number, have significant impact on the overall performance of the heat exchanger mounted with ribs. It has also been reported that the
CFD-Taguchi scheme can be employed easily and also economically for a reliable and robust optimization (Wang et al. 2009; Aghaie et al. 2015). Therefore, the
present research work is primarily concentrated on the prediction of best rib design
parameters for a ribbed SAH using Taguchi method. The ribs have been provided
on the bottom surface, which was exposed to constant heat flux. Firstly, the profound impacts of design parameters, i.e. rib geometry (see Fig. 6.1), rib spacing and