Dimple structure is an effective heat transfer augmentation approach on coolant channel due to its advantage on pressure penalty. The implication of secondary protrusion, which indicates protrusion with smaller dimension than dimple, will intensify the Nusselt number Nu inside dimple cavity without obvious extra pressure penalty. The objective of this study is to numerically analyze the combination effect of dimples and secondary protrusion. Different protrusion–dimple configurations including protrusion print-diameter Dp, protrusion–dimple gap P, and staggered angle α are investigated. From the results, it is concluded that the implication of secondary protrusion will considerably increase the heat transfer rates inside dimple cavity. Cases 4 and 6 possess the highest Nusselt number enhancement ratio Nu/Nu0 reaching up to 2.1–2.2. The additional pressure penalty brought by the protrusion is within 15% resulting in total friction ratio f/f0 among the range of 1.9–2.1. Dimpled channels with secondary protrusions possess higher thermal performance factor TP, defined as (Nu/Nu0)/(f/f0)1/3, among which cases 4 and 6 are the optimal structures. Besides this, the TP of protrusion–dimple channels are comparable to the other typical heat transfer devices, and higher TP can be speculated after a more optimal dimple shape or combination with ribs and fins.

References

References
1.
Lau
,
S. C.
,
McMillin
,
R. D.
, and
Han
,
J. C.
,
1991
, “
Heat Transfer Characteristics of Turbulent Flow in a Square Channel With Angled Discrete Ribs
,”
ASME J. Turbomach.
,
113
(
3
), pp.
367
374
.
2.
Han
,
J. C.
,
1988
, “
Heat Transfer and Friction Characteristics in Rectangular Channels With Rib Turbulators
,”
ASME J. Heat Transfer
,
110
(
2
), pp.
321
328
.
3.
Zhang
,
Y. M.
,
Gu
,
W. Z.
, and
Han
,
J. C.
,
1994
, “
Heat Transfer and Friction in Rectangular Channels With Ribbed or Ribbed-Grooved Walls
,”
ASME J. Heat Transfer
,
116
(
1
), pp.
58
65
.
4.
Ligrani
,
P. M.
, and
Mahmood
,
G. I.
,
2003
, “
Spatially Resolved Heat Transfer and Friction Factors in a Rectangular Channel With 45-Deg Angled Crossed-Rib Turbulators
,”
ASME J. Turbomach.
,
125
(
3
), pp.
575
585
.
5.
Ligrani
,
P. M.
,
Oliveira
,
M. M.
, and
Blaskovich
,
T.
,
2003
, “
Comparison of Heat Augmentation Techniques
,”
AIAA J.
,
41
(
3
), pp.
337
362
.
6.
Afanasyev
,
V. N.
,
Chudnovsky
,
Y. P.
, and
Leontiev
,
A. I.
,
1993
, “
Turbulent Flow Friction and Heat Transfer Characteristics for Spherical Cavities on a Flat Plate
,”
Exp. Therm. Fluid Sci.
,
7
(
1
), pp.
1
8
.
7.
Griffith
,
T. S.
,
Luai
,
A.
, and
Han
,
J.
,
2003
, “
Heat Transfer in Rotating Rectangular Cooling Channels (AR = 4) With Dimples
,”
ASME J. Turbomach.
,
125
(
3
), pp.
555
564
.
8.
Elyyan
,
M. A.
, and
Danesh
,
K. T.
,
2010
, “
Effect of Coriolis Forces in a Rotating Channel With Dimples and Protrusions
,”
Int. J. Heat Fluid Flow
,
31
(
1
), pp.
1
18
.
9.
Elyyan
,
M. A.
, and
Danesh
,
K. T.
,
2012
, “
Investigation of Coriolis Forces Effect of Flow Structure and Heat Transfer Distribution in a Rotating Dimpled Channel
,”
ASME J. Turbomach.
,
134
(
3
), pp.
1
8
.
10.
Ligrani
,
P. M.
,
Harrison
,
J. L.
, and
Mahmmod
,
G. I.
,
2001
, “
Flow Structure Due to Dimple Depressions on a Channel Surface
,”
Phys. Fluids
,
13
(
11
), pp.
3442
3451
.
11.
Ligrani
,
P. M.
,
Mahmood
,
G. I.
,
Harrison
,
J. L.
,
Clayton
,
C. M.
, and
Nelson
,
D. L.
,
2001
, “
Flow Structure and Local Nusselt Number Variation in a Channel With Dimples and Protrusions on Opposite Walls
,”
Int. J. Heat Mass Transfer
,
44
(
23
), pp.
4413
4425
.
12.
Mahmood
,
G. I.
,
Sabbagh
,
M. Z.
, and
Ligrani
,
P. M.
,
2001
, “
Heat Transfer in a Channel With Dimples and Protrusions on Opposite Walls
,”
J. Thermophys. Heat Transfer
,
15
(
3
), pp.
275
283
.
13.
Burgess
,
N. K.
, and
Ligrani
,
P. M.
,
2005
, “
Effects of Dimple Depth on Channel Nusselt Numbers and Friction Factors
,”
ASME J. Heat Transfer
,
127
(
8
), pp.
839
847
.
14.
Elyyan
,
M. A.
, and
Tafti
,
D. K.
,
2012
, “
Investigation of Coriolis Forces Effect of Flow Structure and Heat Transfer Distribution in a Rotating Dimpled Channel
,”
ASME J. Turbomach.
,
134
(
3
), p.
031007
.
15.
Alshroof
,
O.
,
Reizes
,
J.
,
Timchenko
,
V.
, and
Leonardi
,
E.
,
2009
, “
Flow Structure and Heat Transfer Enhancement in Laminar Flow With Protrusions–Dimple Combinations in a Shallow Rectangular Channel
,”
ASME
Paper No. HT2009-88251.
16.
Hwang
,
S. D.
,
Kwon
,
H. G.
, and
Cho
,
H. H.
,
2010
, “
Local Heat Transfer and Thermal Performance on Periodically Dimple–Protrusion Patterned Walls for Compact Heat Exchangers
,”
Energy
,
35
(
12
), pp.
5357
5364
.
17.
Chang
,
S. W.
,
Chiang
,
K. F.
, and
Chou
,
T. C.
,
2010
, “
Heat Transfer and Pressure Drop in Hexagonal Ducts With Surface Dimples
,”
Exp. Therm. Fluid Sci.
,
34
(
8
), pp.
1172
1181
.
18.
Han
,
J. C.
,
Zhang
,
Y. M.
, and
Lee
,
C. P.
,
1991
, “
Augmented Heat Transfer in Square Channels With Parallel, Crossed and V-Shaped Angled Ribs
,”
ASME J. Heat Transfer
,
113
(
3
), pp.
590
596
.
19.
Taslim
,
M. E.
,
Li
,
T.
, and
Kercher
,
D.
,
1996
, “
Experimental Heat Transfer and Friction in Channels Roughened With Angle, V-Shaped and Discrete Ribs on Two Opposite Walls
,”
ASME J. Turbomach.
,
118
(
1
), pp.
20
28
.
20.
Chyu
,
M. K.
,
Yu
,
Y.
,
Ding
,
H.
,
Downs
,
J. P.
, and
Soechting
,
F. O.
,
1997
, “
Concavity Enhanced Heat Transfer in an Internal Cooling Passage
,”
ASME
Paper No. 97-GT-437.
21.
Shen
,
Z. Y.
,
Qu
,
H. C.
,
Zhang
,
D.
, and
Xie
,
Y. H.
,
2013
, “
Effect of Bleed Hole on Flow and Heat Transfer Performance of U-Shaped Channel With Dimple Structure
,”
Int. J. Heat Mass Transfer
,
66
, pp.
10
22
.
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