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Heat Transfer Engineering

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Heat Transfer Augmentation of a Co-Rotating Disk Assembly with Special Emphasis on the Lower Disk N. Sanieia; E. D. Erturana; A. B. Olcaya a Department of Mechanical and Industrial Engineering, Southern Illinois University Edwardsville, Edwardsville, Illinois, USA

To cite this Article Saniei, N. , Erturan, E. D. and Olcay, A. B.(2004) 'Heat Transfer Augmentation of a Co-Rotating Disk

Assembly with Special Emphasis on the Lower Disk', Heat Transfer Engineering, 25: 4, 80 — 89 To link to this Article: DOI: 10.1080/01457630490443811 URL: http://dx.doi.org/10.1080/01457630490443811

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Heat Transfer Engineering, 25(4):80–89, 2004 C Taylor & Francis Inc. Copyright  ISSN: 0145-7632 print / 1521-0537 online DOI: 10.1080/01457630490443811

Heat Transfer Augmentation of a Co-Rotating Disk Assembly with Special Emphasis on the Lower Disk Downloaded By: [informa internal users] At: 16:15 21 June 2010

N. SANIEI, E. D. ERTURAN, and A. B. OLCAY Department of Mechanical and Industrial Engineering, Southern Illinois University Edwardsville, Edwardsville, Illinois, USA

Experiments were performed to map local heat transfer coefficients on an unobstructed co-rotating disk system simulating the internal component of a computer disk drive assembly. The disk diameter was twice as large as a hard drive, and the rotational speed up to 5000 rpm was studied. The effects of two parameters, on the heat transfer phenomena the Reynolds number from 6.587 × 104 to 3.096 × 105 and the non-dimensional disk-to-disk ratio (L/D) from 0.02 to 0.06, were observed. The disks were positioned horizontally, and heat transfer was measured for the top faces of both disks. Emphasis is given to the top face of the lower disk in this research, as less experimental data are available in the literature. A transient liquid crystal technique was employed for the measurements, and the results reveal an interesting pattern of the heat transfer rate in the gap for the upper surface of the lower disk. The overall heat transfer is much lower for the surface of the lower disk as compared to that of the top disk. The maximum average heat transfer rate was established to be at L/D = 0.04 for the case with the highest rotational speed.

LITERATURE AND BACKGROUND

disk. The aim of this study is to understand the fluid flow and heat transfer characteristics of a co-rotating disk at high rotational speeds. As the processor speed increases significantly, more heat is generated within the computers, and disks are subject to more thermal loading than ever in their enclosed boundaries. The excess heat generated causes thermal expansion on data storing disk surfaces and increases thermally induced vibration on the co-rotating disk structures. Under such conditions, the heat transfer characteristics gain significant importance in order to prevent the failure of the system. Although heat transfer from co-rotating disks has been investigated by some researchers, very few experimental results are available in the literature for

Computer disk drives, passenger car disk brake systems, and gas turbine rotors are a few examples where rotating components are part of an assembly. While a disk is rotating in an enclosed environment, heat may be generated by various components. The transfer of heat through proper cooling will enhance disk life as well as ensure the stability and integrity of the system; for example, for a typical computer hard disk, better performance can be achieved by the faster rotation of the Address correspondence to Dr. Nader Saniei, Department of Mechanical and Industrial Engineering, Southern Illinois University Edwardsville, Edwardsville, IL 62026-1805. E-mail: [email protected]

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the heat transfer characteristics of the lower disk. This could be due to the limitation imposed by rotation on the experimental instrumentations. The following literature covers some recent experimental works done on heat transfer from rotating disks and includes samples of fluid flow and heat transfer literature for single rotating as well as co-rotating systems. Kreith et al. [1] obtained experimental data for heat and mass transfer from a rotating aluminum disk. A crystal grade naphthalene technique was used during mass transfer measurements to demonstrate the strong relationship between the mass transfer rate and Reynolds number. At high Reynolds number values, the rate of mass transfer was enhanced. Young [2] studied convective heat transfer from an internally heated rotating disk facing upwards in the ambient air with an experimental approach and compared his results with the analytical solutions. He determined heat transfer coefficients by monitoring surface and ambient temperatures and disk rotational speed. Elkins and Eaton [3] determined the local Nusselt number distribution in the boundary layer of a rotating disk and utilized the constant heat flux boundary conditions on a free rotating disk surface at Reynolds numbers ranging from 8.0 × 104 to 8.5 × 105 . Chen et al. [4] also investigated heat and mass transfer on rotating disks. For mass transfer measurements, a naphthalene sublimation technique was utilized. They conducted experiments on both rotating and stationary disks with jet impingement in order to analyze the effects of rotation and jet impingement separately. Gan et al. [5] described a combined computational and experimental study of heat transfer in a rotating cavity with a peripheral inflow and outflow of cooling air for a range of rotational speeds and flow rates. Both computed and measured values of the radial component of velocity confirmed the recirculating nature of the flow. Dyban and Kabkov [6] studied flow in a gap formed by rotating disks. They used two identical disks with a 20 cm diameter and conducted experiments in the ranges of 0.0345 < L/D < 0.045 and 3.6 × 105 < Re < 6.5 × 105 . They concluded that for the studied L/D and Reynolds number ranges, the fluid boundary layers on the disk surfaces facing the air gap do not merge and the flow was turbulent. It was also stated that airflow rates were stabilized in the center zone of the peripheral region and the flow was directed inwards (towards the axis of rotation), whereas the flow in the bottom and top boundary layers was directed outwards (away from the axis of rotation). Simand et al. [7] analyzed flow characteristics of a confined vortex between two parallel disks rotating around the same axis in a cylindrical enclosure with an L/D ratio of 0.844. They reported a stable vortex just outside the gap near the lateral wall heat transfer engineering

and a solid body rotation in the gap, with a tangential velocity increasing linearly with the radius and an almost null velocity component along the radius when two disks rotate at the same rotational speed. It was also stated that due to the vortex at the lateral walls, flow was penetrating the gap around the mid-plane between the disks and disturbing the solid body rotation in the entry region. Soong and Yan [8] conducted a numerical study of mixed convection between co-rotating heated disks with a special emphasis on the centrifugal buoyancy effect. They concluded that the rotational-induced buoyancy effect alters the flow and heat transfer characteristics and should be considered in convection studies. Mochizuki and Inoue [9] studied local heat transfer coefficients along the radius in a passage formed by two parallel rotating disks. The flow was radially outward, and their study included cases with a low source flow rate and a higher rotating speed, which creates a rotating stall. The effect of self-sustained periodic flow separation as well as rotating stall was determined and mechanisms were explained. Chang et al. [10] performed a numerical study for flow and heat transfer in the space between two co-rotating disks. They concluded that in the absence of throughflows, the structure of the flow varies from solid body rotation near the hub to a strongly sheared flow in the vicinity of the shroud wall. Morse [11] computationally predicted streamlines for flow in rotor-stator geometry as well as for co-rotating and counter-rotating disks. His numerical results for the co-rotating case show asymmetrically re-circulating zones extending inside the gap between the disks. Their Reynolds numbers varied between 105 and 106 , and the gap ratio between the disks was fixed at 0.1. Tzeng and Chang [12] used Laser Doppler Anemometry to measure flow between four shrouded co-rotating disks. They showed that a globally oscillatory motion exists for the disk drive flow with a small amount of obstruction between the disks. Such oscillatory motion influences the radial transport and distribution of the variables such as circumferential velocity component. Tzeng and Humphrey [13] presented numerical results for flow in a co-rotating disk similar to the geometry used by Tzeng and Chang [12]. The contour plot of their predicted streamlines shows recirculation cells near the enclosed wall and in the gap, which extends into the core along the symmetry plane. Humphrey et al. [14] presented a summary review on unobstructed and obstructed rotating disk flows. Thermochromic liquid crystals (TLC), displaying a color hue at certain temperature ranges, are widely used for measuring heat transfer from surfaces in internal and external flows. Many experimental researchers used TLC in transient thermal analysis because of their high accuracy and reliability. Metzger et al. [15] investigated vol. 25 no. 4 2004

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heat transfer with a transient liquid crystal technique on a rotating disk with jet impingement. Saniei and Yan [16] studied heat transfer from a single disk rotating in an infinite environment and enhanced by jet impingement cooling. Accuracy of TLC technique is sometimes questioned by researchers that had reported a rotational shift and discrepancies between liquid crystal readings and thermocouple readings. Two different research groups, Camci and Glezer [17] and Syson et al. [18], examined the effects of rotational speed on liquid crystal surface temperature measurements at rotational speeds up to 7500 rpm. Both groups reported no significant effect of rotational speed on either narrow-band or wide-band liquid crystal readings. This research aims to provide experimental data on local heat transfer of a co-rotating structure and analyze the effects of geometric factors such as distance between co-rotating disk surfaces and rotational speeds on the thermal phenomena. The data provided in this research will lead to a better understanding of heat transfer characteristics of co-rotating structures and provide necessary information for the design of such systems to improve their operational efficiencies. As a result of the developments in the computer technology, a typical hard disk drive system is more compact, has higher storage capacity, and weighs and costs less than ever. Current computer hard disks have a diameter of 9.5 cm and operate in the range of 5,400–10,000 rpm, resulting in an 8 × 104 < Re = R 2 ω/υ < 1.5 × 105 operating condition. In this study, 20 cm diameter test disks were used at rotational speeds from 1,000 rpm to 4,700 rpm, resulting in a Reynolds number range from 6.587 × 104 to 3.096 × 105 . Moreover, L/D values from 0.02 to 0.06 were studied in these experiments in order to understand

Figure 1

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the effects of disk-to-disk distance on local and average heat transfer.

EXPERIMENTAL TECHNIQUE Experimental apparatus consisted of the following: a co-rotating disk setup, a temperature controlled environment, and a DC motor, and a data acquisition system with an image recording and analyzing system. The co-rotating setup was made of two 20 cmdiameter transparent Plexiglas disks with 0.45 cm thickness mounted on the same shaft with an adjustable distance from each other. The top surfaces of the upper disk and the bottom disk were considered for heat transfer measurements and covered with liquid crystals in order to observe isotherms on the surfaces under study. Before spraying the liquid crystals, the surfaces were painted black to provide a non-transparent background for better observation of the liquid crystal color display on the surfaces. Local points were marked white with the increments of r/R = 0.1 in order to differentiate the liquid crystals color displays at each location during each experiment. In order to observe and record data on the lower disk, the top disk was replaced with a transparent disk during the second phase of measurements while focusing on the lower disk. Figure 1 shows the co-rotating disk experimental setup with the lower disk covered with liquid crystals and the upper disk being transparent. A thermally insulated oven equipped with heating elements and thermocouples was used as the temperaturecontrolled test environment. A sliding door was placed on the top of the oven to seal the test environment. The

Experimental apparatus.

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door was kept closed during the heating period and removed at the beginning of the experiment in order to allow the sudden exposure of the test section to the ambient air. Once the sliding door was removed, the test section could be seen clearly by the video camera connected to the recording system. Two light bulbs controlled by a data acquisition system were used as heating elements in the insulated enclosure. During the initial heating period, the temperature of the test enclosure was controlled by the data acquisition system through four thermocouples placed in the oven in the following manner one above the upper disk, one in the corner of the gap between the two disks, and two at opposite corners at the bottom of the test section. A DC motor controlled by a power supply was used to rotate the co-rotating disks setup with the desired rotational speeds. The clearance between the disk setup and four side walls of the enclosure was kept at 12 cm.

EXPERIMENTAL PROCEDURE Experiments were performed at five rotational speeds for five different L/D ratios for the lower disk. A similar procedure was followed when measuring heat transfer from the upper disk regardless of L/D ratio. After the disk-to-disk distance was set to the desired L/D ratio, the co-rotating disk fixture was placed in the enclosed oven and mounted on the motor. After the cover was placed and the test setup was thermally isolated, the oven was heated up to 40◦ C for 1 hour (15 minutes without rotation, and 45 minutes with rotation). Uniform oven temperature of 40◦ C was reached in 15 minutes of initial heating, and the motor set to the desired

Figure 2

rotational speed was activated to obtain steady state flow conditions. After a one-hour heating period, steady-state thermal and flow boundary conditions required for the experiments were reached within the enclosed volume. With the camcorder and timer ready (facing the oven’s removable door), the experiment started by shutting down the heating and removing the oven door simultaneously. After the cover was removed, the transient cooling times and the propagation of the liquid crystals color bands (rings) indicating a 35◦ C disk surface temperature were recorded. Local heat transfer coefficient data were obtained based on the transient solution of a one-dimensional conduction equation for a semi-infinite solid body: Ts − T∞ 2 = eγ erfc(γ) Ts,i − T∞

(1)

∞ where TTs,is −T −T∞ is the non-dimensional surface temperature (T ∗ ) and γ is related to heat transfer coefficient by the following equation:

 ht = γ

ρC p k t

RESULTS AND DISCUSSION Heat Transfer from Upper Disk Figure 2 displays local Nusselt numbers at a rotational speed of 5000 rpm for the surface of the upper disk of the co-rotating assembly. This corresponds to a disk Reynolds number of 3.43 × 105 . Reynolds numbers

Local Nusselt number comparison between experimental and analytical [19] results for Re = 3.43 × 105 .

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and local Nusselt numbers are defined as Re = R 2 ω/υ and Nu = h D/kair , respectively. The results are shown for the entire region except for the central hub, which occupied up to r/R = 0.4 of the radial position. For the upper disk (similar to a single rotating disk), it has been established that the local critical Reynolds number (Rer = r 2 ω/υ) where transition from laminar to turbulent flow takes place is around 2.3 × 105 –2.5 × 105 . As seen from Figure 2, the heat transfer slope starts to change around r/R = 0.65, which corresponds to a local Reynolds number of 2.2 × 105 . This implies that the flow has gone into transition to turbulent regime at this radial interval for this particular rpm. The heat transfer rate increases with a mild slope in the laminar region, whereas in the turbulent region (r/R > 0.7), it increases with a sharper slope. The results are compared against the correlation given by Cobb and Saunders [19] and shown on the same graph. Although the correlation is shown for the entire radial region of the disk, it is said to be more accurate for turbulent region. The present experimental results show higher Nusselt numbers for turbulent regime, where Rer exceeds that of 2.5 × 105 . This could be due to the existence of the hub at the center of the experimental setup. Figure 3 demonstrates the comparison of the experimental results for Nusselt number distributions at different Reynolds numbers. Transition from laminar to turbulent flow is observed at the same local Reynolds number of 2.2 × 105 , and higher heat transfer rates are obtained for higher Reynolds numbers at a given radial position. The two lowest curves show a case where

Figure 3

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flow remains laminar up to 70–80 percent of the radial location on the disk surface. Heat Transfer from Lower Disk With the co-rotating disk setup, experiments were performed for rotational speeds of 1000, 2200, 3000, 4000, and 4700 rpm with non-dimensional disk-to-disk spacing (L/D) varying from 0.02 to 0.06. The heat transfer rate was measured for the top surface of the lower disk (the surface facing the gap between the disks). For a non-dimensional disk-to-disk distance of L/D = 0.02 and 0.05, the local heat transfer coefficients are given in Figures 4 and 5, respectively, for different rotational speeds. Since the motor shaft and disk mounting fixture occupy the central area of the lower disk, the heat transfer data from r/R = 0.2 to 1 are presented in the graphs. For L/D = 0.05, heat transfer rates increase with relatively mild slopes for the region closer to the central hub and are followed by a region with a sharper slope at the middle section that levels off as it gets closer to the outer edge of the disk. For L/D = 0.02, the heat transfer rates increase almost linearly as shown in Figure 4 for all Reynolds numbers. For all cases, the central region of the lower disk experiences very low heat transfer rate. The definition of the laminar, transition, and turbulent flow regime that have been established for the single disk (upper disk) may be applied to the lower disk of the co-rotating assembly, but the critical Reynolds number for transition to turbulent may not be the same. The

Nusselt number vs. location for a single disk at different rotating speeds.

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Figure 4

Local Nusselt number for L/D = 0.02 at different Reynolds numbers.

fluid flow behavior in the gap between two disks is governed by the amount and extent of the air penetrating into the gap. During the rotational motion, cross-stream flow will penetrate symmetrically into the gap between the disks up to a critical radius. Tzeng and Chang [12] and Humphrey et al. [14] confirmed this flow behavior, and it seems to be valid for both obstructed as well as unobstructed co-rotating disk geometries. The strength of the radial flow and its penetration depth depend on two parameters: the non-dimensional gap between the disks and the rotational speed. A smaller gap dimension or a lower rotational speed results

Figure 5

in a shorter penetrating radius or weaker re-circulation zones, respectively, and consequently lower heat transfer rates. Figure 6 compares heat transfer data for various L/D ratios at Re = 3.096 × 105 . For smaller L/D cases, strong re-circulating regions exist at the outer edge of the gap between the co-rotating disks. For larger L/D cases, the re-circulating flow extends further towards the midsection of the disk. These re-circulation zones lose their strength and effectiveness in removing heat as they get closer to the center. The effect of rotational speed is demonstrated in Figures 4 and 5, where higher heat transfer rates are observed at higher Reynolds

Local Nusselt number for L/D = 0.05 at different Reynolds numbers.

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Figure 6

Local Nusselt number for Re = 3.096×105 for different L/D ratios.

numbers for a fixed L/D ratio. Between r/R = 0.2 and r/R = 0.4, the flow in the gap approaches that of a solid-body rotation. That is why the central region of the lower disk experiences the lowest heat transfer rate in all cases. On the other hand, depending on the L/D ratio and Reynolds number, the imbalance between the inwardly directed pressure gradient and the outwardly directed centrifugal force causes the cross-stream flows for 0.7 < r/R < 1.0. Those with high turbulent kinetic energy enter into the core along the symmetry plane.

Figure 7

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The higher rate of heat transfer at the mid-plane and the outer edge of the gap may be attributed to these secondary flows. The overall local heat transfer rates and average Nusselt numbers are considerably lower for the lower disk as compared to the upper disk for all L/Ds studied. For comparison, the local Nusselt number values are presented in Figure 3 for the upper disk, and in Figures 4 and 5 for the lower disk. Moreover, average Nusselt numbers versus L/D are plotted in Figure 7 for various Reynolds

Average Nusselt number vs. L/D for different Reynolds numbers.

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Figure 8

T ∗ distribution at Re = 3.096 × 105 for different L/D ratios.

numbers. For each Reynolds number, there exists an optimum L/D at which an average Nusselt number reaches its maximum. The heat transfer rate reaches its maximum at L/D = 0.04 for higher Reynolds numbers and at L/D = 0.05 for lower Reynolds numbers. As the L/D ratio approaches zero, the co-rotating assembly behaves like a rigid body rotation; when the gap becomes larger than a certain distance, the overall heat transfer rate starts to decrease due to the decoupling effect between the two disks. In the analysis of the dynamic behavior of a rotating disk, surface temperature distribution is needed as an input boundary condition. For this reason, the surface temperature distribution for the rotating disk is obtained by a back calculation scheme. Because of the transient nature of these experiments, temperature distributions may be obtained at every instant of time by inserting the local values of heat transfer coefficient back into the one-dimensional heat conduction equation for a semiinfinite solid body at a particular time. Figure 8 compares temperature distributions for five different L/Ds on the surface of the lower disk.

are the major contributors to the uncertainties. In addition to the usual uncertainty analysis for these types of measurements, uncertainty exists in the position readings for the liquid crystal color display. This is a function of the camera’s viewing angle and temperature gradient at the positions that the temperature readings are taken. For example, points with lower temperature gradients are expected to introduce higher uncertainties because they demonstrate wider color play rather than a distinct ring representing an isotherm at a single location. The uncertainty due to the position reading is estimated to be 1–2 mm for the high temperature gradient regions and 2–3 mm on the low temperature gradient regions. An assumption of a one-dimensional semi-infinite solid solution will be valid if the penetration depth for a given experimental run is less than the thickness of the object under study. As the duration of an experiment increases, so does the penetration depth of conduction; therefore, there are more uncertainties introduced for those runs requiring longer time. These include cases of low Reynolds numbers, particularly for the lower disk, where the rate of heat transfer is slow. Table 1

Uncertainty analysis

UNCERTAINTY ANALYSIS

Variable X i

Uncertainty analysis was done following the outline by Kline and McClintock [20], for all the parameters that had factored into the calculation of Nusselt number. Table 1 shows a sample uncertainty analysis for a typical experiment run. The Nusselt number uncertainty was calculated to be around 10%, where time, liquid crystal temperature, ambient temperature, and radiation

t (ρ∗ C ∗p k)0.5 Ts Ts,i Tamb ε kair D

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Typical value

Uncertainty δX i

38.54 (sec) 0.033 569 (kg/K-s5/2 ) 28.45 35.4 (◦ C) 0.2 40 (◦ C) 0.2 22 (◦ C) 0.5 0.7 0.1 0.0263 (W/m-K) 0.000263 0.2 0.001

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δX i Nu

×

δNu δX i

× 100

0.050 1.027 6.077 4.407 6.018 2.411 1.000 0.584

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CONCLUSIONS

Greek Symbols

An experimental study on a co-rotating disk assembly using a transient liquid crystal technique was conducted for a non-dimensional disk-to-disk distance (L/D) from 0.02 to 0.06 and Reynolds numbers from 6.587 × 104 to 3.096 × 105 to simulate the computer disk drive operating conditions. The following are the conclusions of this study.

ω ρ υ γ





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• •





Local heat transfer distribution from the top disk is fairly independent of the radial location in the laminar region but increases sharply when flow becomes turbulent. Heat transfer from the top surface of the lower disk was considerably lower than the heat transfer from the top surface of the upper disk. Strong re-circulating zones exist near the outer edge of the gap between the two disks. The rate of heat transfer between the two disks depends on the strength of the re-circulating zones as well as the extent by which they penetrate the gap. Rotational speed is dominant on heat transfer characteristics. Heat transfer is enhanced with increasing rotational speed for both upper and lower disk at all L/Ds. Average heat transfer is maximized at L/D = 0.05 for Re = 6.587 × 104 and at L/D = 0.04 for Re = 3.096 × 105 . As the rotational speed increases, heat transfer tends to reach maximum at a lower L/D.

NOMENCLATURE Cp D h ht k kair L L/D Nu Nuavg r R Re Rer r/R t Ts Ts,i T∞ T∗ 88

Plexiglas specific heat, J/kgK disk diameter, m convective heat transfer coefficient, W/m2 K total heat transfer coefficient, W/m2 K Plexiglas thermal conductivity, W/mK air thermal conductivity, W/mK disk-to-disk distance, m non-dimensional disk-to-disk distance local Nusselt number, h D/kair average Nusselt number local radius, m disk radius, m rotational Reynolds number, ωR 2 /υ local rotational Reynolds number, ωr 2 /υ non-dimensional radial disk location transient cooling time, s surface temperature, ◦ C initial surface temperature, ◦ C ambient temperature, ◦ C ∞ non-dimensional surface temperature, TTs,is −T −T∞ heat transfer engineering

disk rotational speed, rad/s Plexiglas density, kg/m3 kinematic viscosity of air, m2 /s non-dimensional parameter in semi-infinite body assumption

REFERENCES [1] Kreith, F., Taylor, J. H., and Chong, J. P., Heat and Mass Transfer from a Rotating Disk, ASME Journal of Heat Transfer, vol. 81, pp. 95–104, 1959. [2] Young, R. L., Heat Transfer from a Rotating Plate, Transactions of the ASME, August, pp. 1163–1168, 1956. [3] Elkins, C., and Eaton, J. K., Heat Transfer Measurements in the Boundary Layer on a Rotating Disk, ASME Winter Annual Meeting, HTD, vol. 271, pp. 193–200, 1994. [4] Chen, J. X., Ben, X., and Owen, J. M., Heat Transfer from Air-Cooled Contra-rotating Disks, Journal of Turbomachinery, vol. 119, pp. 61–67, 1997. [5] Gan, I., Wilson, X., Owen, J. M., Heat Transfer in a Rotating Cavity with a Peripheral Inflow and Outflow of Cooling Air, Journal of Turbomachinery, vol. 120, pp. 818–823, 1998. [6] Dyban, Y. P., and Kabkov, V. Y., Experimental Study of Flow of Air in a Gap Formed by Two Rotating Disks, Fluid MechanicsSoviet Research, vol. 8, no. 4, pp. 99–104, 1979. [7] Simand, C., Chilla, F., and Pinton, J. F., Structure, Dynamics and Turbulence Features of a Confined Vortex, Springer Online Publications, Lecture Notes in Physics, vol. 0555, 2000. [8] Soong, C. Y., and Yan, W. M., Numerical Study of Mixed Convection between Two Co-rotating Symmetrically Heated Disks, Journal of Thermophysics and Heat Transfer, vol. 7, No. 1, pp. 165–170, 1993. [9] Mochizuki, S., and Inoue, T., Self-Sustained Flow Oscillations and Heat Transfer in Radial Flow Through Co-Rotating Parallel Disks, Experimental Thermal and Fluid Science, vol. 3, pp. 242–248, 1990. [10] Chang, C. J., Schuler, C. A., Humphrey, J. A. C., and Greif, R., Flow and Heat Transfer in Space Between Two Co-rotating Disks in an Axisymmetric Enclosure, Journal of Heat Transfer, vol. 111, pp. 625–632, 1989. [11] Morse, A. P., Assessment of Laminar-Turbulent Transition in Closed Disk Geometries, Journal of Turbomachinery, vol. 113, pp. 131–138, 1991. [12] Tzeng, H. M., and Chang, C. J., Obstructed Flow between Shrouded Co-rotating Disks, it Phys. Fluids A, vol. 3, pp. 484– 486, 1991. [13] Tzeng, H. M., and Humphrey, J. A. C., Corotating Disk Flow in an Axisymmetric Enclosure with and without a Bluff Body, International Journal of Heat and Fluid Flow, vol. 12, No. 3, pp. 194–201, 1991. [14] Humphrey, J. A. C., Chang, C. J., and Schuler, C. A., Unobstructed and Obstructed Rotating Disk Flows: A Summary Review Relevant to Information Storage Systems, ASME Winter Annual Meeting, Dallas, TX, November 25–30, 1990. [15] Metzger, D. E., Bunker, R. S., and Bosch, G., Transient Liquid Crystal Measurement of Local Heat Transfer on a Rotating Disk with Jet Impingement, Transactions of the ASME, vol. 113, pp. 52–59, 1991. [16] Saniei, N., and Yan, X., An Experimental Study of Heat Transfer from a Disk Rotating in an Infinite Environment Including

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[17]

[18]

[19]

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[20]

Heat Transfer Enhancement by Jet Impingement Cooling, Journal of Enhanced Heat Transfer, vol. 7, pp. 231–245, 2000. Camci, C., and Glezer, B., Liquid Crystal Thermography on the Fluid Solid Interface of Rotating Systems, Journal Heat Transfer, vol. 119, pp. 20–29, 1997. Syson, B. J., Pilbrow, R. G., and Owen, J. M., Effect of Rotation on Temperature Response of Thermochromic Liquid Crystal, International Journal of Heat and Fluid Flow, vol. 17, no. 5, pp. 491–499, 1996. Cobb, E. C., and Saunders, O. A., Heat Transfer from a Rotating Disk, Proc. Roy. Soc. London, Ser. A 236, pp. 343–351, 1956. Kline, S. J., and McClintock, F. A., Describing Uncertainties in Single Sample Experiments, Mechanical Engineering, vol. 75, pp. 3–8, 1953.

particular, he has been involved with transient and steady-state visualization techniques for local heat transfer measurements using liquid crystals.

Nader Saniei is the department head and professor of Mechanical Engineering at Southern Illinois University Edwardsville. He received his Ph.D. in 1988 from the University of California Davis and joined Southern Illinois University Edwardsville in 1990 as an Assistant Professor. His research area has been in heat transfer enhancement techniques for channel flows, electronic cooling, and flow visualizations. In

Ali Bahadir Olcay received his Bachelor of Science from Middle East Technical University, Ankara, Turkey, and Master of Science from Southern Illinois University Edwardsville in Mechanical Engineering. He is currently a lecturer and a Ph.D. student at the Southern Methodist University, Dallas, Texas. Lately he has been working on heat transfer and fluid flow characteristics of the rotating disk structures.

heat transfer engineering

Evren D. Erturan is currently a Design & Development Engineer at Watlow Electric Manufacturing Company in St. Louis, Missouri. He received his B.S. at Middle East Technical University, Turkey, and M.S. at Southern Illinois University Edwardsville in Mechanical Engineering. He worked on experimental heat transfer on corotating disk structures during his graduate study.

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