An experimental study was carried out to investigate the heat transfer and friction characteristics of a fully developed turbulent air flow in a square channel with 45 deg inclined ribs on one, two, or four walls. Either two opposite walls or all four walls in the channel were heated. Tests were performed for Reynolds numbers (Re) ranging from 7600 to 24,900, the pitch to rib height ratio $(P∕e)$ of 8.0, the rib height to channel hydraulic diameter ratio $(e∕Dh)$ of 0.0667, and the channel aspect ratio of 1.0. The results show that the local Nusselt number and friction factor increase with the number of ribbed walls. With one ribbed wall, the Nusselt numbers on the ribbed side (B) were 50% and 63% greater than those on the adjacent smooth sides (L∕R) and the opposite smooth side (T), respectively. The Nusselt numbers, when the two opposite walls of a four-wall ribbed channel are heated, are found to be 1.49–1.52 times greater than those obtained when all four walls are heated.

1.
Han
,
J. C.
,
Park
,
J. S.
, and
Lei
,
C. K.
, 1985, “
Heat Transfer Enhancement in Channels With Turbulence Promoters
,”
ASME J. Eng. Gas Turbines Power
0742-4795,
107
, pp.
629
635
.
2.
Han
,
J. C.
, and
Park
,
J. S.
, 1988, “
Developing Heat Transfer in Rectangular Channels With Rib Turbulators
,”
Int. J. Heat Mass Transfer
0017-9310,
31
, pp.
183
195
.
3.
Chandra
,
P. R.
,
Niland
,
M. E.
, and
Han
,
J. C.
, 1997, “
Turbulent Flow Heat Transfer and Friction in a Rectangular Channel With Varying Numbers of Ribbed Walls
,”
ASME J. Turbomach.
0889-504X,
119
, pp.
374
380
.
4.
Micheal
,
F. M.
, 2003,
,
,
New York
, pp.
162
189
.
5.
Sieder
,
E. N.
, and
Tate
,
C. E.
, 1936, “
Heat Transfer and Pressure Drop of Liquids in Tubes
,”
Ind. Eng. Chem.
0019-7866,
28
, pp.
1429
1453
.
6.
Kline
,
S. J.
, and
McClintock
,
F. A.
, 1953, “
Describing Uncertainties in Single Sample Experiments
,”
Mech. Eng. (Am. Soc. Mech. Eng.)
0025-6501,
75
, pp.
3
8
.
7.
Hu
,
Z. J.
, and
Shen
,
J.
, 1996, “
Heat Transfer Enhancement in a Converging Passage With Discrete Ribs
,”
Int. J. Heat Mass Transfer
0017-9310,
39
, pp.
1719
1727
.
8.
El-Husayni
,
H. A.
,
Taslim
,
M. E.
, and
Kercher
,
D. M.
, 1994, “
Experimental Heat Transfer Investigation of Stationary and Orthogonally Rotating Asymmetric and Symmetric Heated Smooth and Turbulated Channels
,”
ASME J. Turbomach.
0889-504X,
116
, pp.
124
132
.