thermo-hydrodynamics of developing flow in a rectangular mini-channel array
DESCRIPTION
Experimental investigations concerning thermo-hydro-dynamics of developing single-phase liquid flow in a rectangular mini-channel array subjected to constant heat flux condition from three sides, insulated from top, are reported.Data compared with relevant conventional theory.It is concluded that conventional theory, which predicts thermo-hydrodynamics of developing internal flows, is well applicable for the channels used in this study; although, transition occurs early.TRANSCRIPT
6th April, 2008
ISHMT-ASME 2010
10HMTC351
4-6 JANUARY 2010IIT BOMBAY
THERMO-HYDRODYNAMICS OF DEVELOPING FLOW IN A RECTANGULAR MINI-CHANNEL ARRAY
Gaurav Agarwal, Manoj Kumar Moharana, Sameer Khandekar *Department of Mechanical EngineeringIndian Institute of Technology Kanpur
Kanpur-208016 (U.P), INDIA
* Tel: +91-512-259-7038, Fax: +91-512-259-7408, E-mail: [email protected]
Developing flows provide very high heat transfer coefficients in the entrance regions and therefore of interest for mini/micro scale high heat flux removal applications.
In general, the conventional theory which predicts thermo-hydrodynamics of internal flows is well applicable for the channels used in this study. No additional physical effects were observed.
Experimental data suggests an early laminar to turbulent transition near Re ≈ 1100. This is primarily attributed to the channel roughness morphology and possibly by corner swirls generated due to the construction of inlet/outlet manifolds of the array.
The experimental and theoretical Poiseuille number (Po) as well as Nusselt number (Nu) are well correlated with the available models for developing flow. Comparison was made with circular channels of equivalent diameter as well as with fully developed flow conditions.
Experimental investigations concerning thermo-hydro-dynamics of developing single-phase liquid flow in a rectangular mini-channel array subjected to constant heat flux condition from three sides, insulated from top, are reported.
Data compared with relevant conventional theory.
It is concluded that conventional theory, which predicts thermo-hydrodynamics of developing internal flows, is well applicable for the channels used in this study; although, transition occurs early.
Need for highly efficient high heat flux removal in mini/microscale heat transfer devices.
Miniaturized high heat flux removal devices have many application, viz., Cooling of electronic components, Compact heat exchangers, Refrigeration systems, Fuel cells, Aerospace thermal systems, and Bio-medical equipments etc.
Necessitates understanding of the underlying transport processes, especially of simultaneously developing flows, as transport of species (mass, momentum and energy) is highly augmented and enhanced during such conditions.
Parameters of interest are: (a) Friction factor: Poiseuille Number (Po), (b) Heat transfer coefficient: Nusselt Number (Nu).
Estimation of Poiseuille Number and local Nusselt number, over rectangular mini-channel array under simultaneously developing flow and constant heat flux condition is reported.
SCHEMATIC LAYOUT OF THE EXPERIMENTAL SETUP
RESULTS: PRESSURE DROP
MINI-CHANNEL ARRAY MADE OF COPPER SUBSTRATE
DETAILS OF THE MINI-CHANNEL ARRAY ASSEMBLY
MicropumpControlvalve
Condenser
Flow meter
Dataacquisition
system
Pressure transducerT
est s
ect
ion
Con
stan
t te
mpe
ratu
er b
ath
Roughness values μm
Ra 3.7
Rz 23.95
Rq 4.6
Rp 10.61
Rt 31.22
(a) ROUGHNESS PROFILE OF A SINGLE CHANNEL USING LASER PROFILOMETER (b) AVERAGE VALUES USED FOR THE ENTIRE ARRAY
EXPERIMENTAL SETUP
VARIATION OF (a) HYDRODYNAMIC ENTRY LENGTH (b) THERMAL ENTRY LENGTH WITH FLOW Re EXPERIMENTAL PRESSURE DROP vs FLOW Re
Po vs. Re FOR THE ARRAY Po vs. Re FOR DEVELOPING LAMINAR FLOW
NuX vs. Re AT DIFFERENT LOCATIONS
COMPARISION OF EXPERIMENTAL AND THEORETICAL VALUES OF Nu FOR LAMINAR FLOW (a) Pr = 3.97, (b) Pr = 3.25
COMPARISION OF EXPERIMENTAL AND THEORETICAL Nu FOR TURBULENT FLOW (a) Pr 3.97 (b) Pr 3.25
SUMMARY AND CONCLUSIONS
Acknowledgements: Department of Science and Technology, Government of India
RESULTS: HEAT TRANSFER
Sieder and Tate Correlation
Stephan and Preuβer correlation
Shah and London correlation
Churchill and Ozoe correlation
x1/ 62
1/ 33/ 2
1/ 2 1/ 32 / 3 2
Nu
4.364 1 Gz / 29.6
Gz /19.041
1 Pr/ 0.0207 1 Gz / 29.6
1/ 3 0.14
h f wNu 1.86 RePr D / L /
1.33
h0.83
h
0.086 RePr D / LNu 4.364
1 0.1Pr ReD / L
h h
1/ 3
h h
Nu 4.364 0.0722 RePr D / L ;RePr D / L 33.3
Nu 1.953 RePr D / L ; RePr D / L 33.3
h
LGz
4RePr D
Shah correlation
Shapiro et al. correlation
Blasius correlation (Turbulent flow)
x 22
1.25 64x 13.74 x2 P 1Po 13.74 x
u x x1 0.00021 x
2xPo 2 P / u x 13.74 / x
hx x / ReD
0.75Po f Re 0.316 Re
INTRODUCTIONABSTRACT
(a)
(b)
Copper substrate
Dittus-Boelter Correlation (Turbulent flow)
Phillips Correlation
2
0.87 0.43x hNu 0.012 1 D / x Re 280 Pr
0.8 0.4Nu 0.023 Re P r
Correlations for Pressure Drop Estimation
Correlations for Heat Transfer Estimation