Flow and heat transfer of confined impingement jets cooling using a 3-D transient liquid crystal scheme

Wang, Ting; Lin, Mingjie; Bunker, Ronald S.

doi:10.1016/j.ijheatmasstransfer.2005.04.020

Cited by 46 publications

(12 citation statements)

References 24 publications

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“…The result yielded by the 1D method was higher, that trend was also observed by [43]. This small difference is explained by the low height of the micro-ribs.…”

Section: Comparison Of 1d and 3d Heat Transfersupporting

confidence: 57%

Experimental and numerical investigation of impingement heat transfer on a flat and micro-rib roughened plate with different crossflow schemes

Xing

Spring

2011

International Journal of Thermal Sciences

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“…The result yielded by the 1D method was higher, that trend was also observed by [43]. This small difference is explained by the low height of the micro-ribs.…”

Section: Comparison Of 1d and 3d Heat Transfersupporting

confidence: 57%

Experimental and numerical investigation of impingement heat transfer on a flat and micro-rib roughened plate with different crossflow schemes

Xing

Spring

2011

International Journal of Thermal Sciences

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“…Brevet et al [18] optimized the spanwise pitch on the basis of cooling efficiency estimated per unit area of impingement surface. More recently, liquid crystal thermography was used to study local heat transfer distribution due to impingement of arrays of multiple jets with spent air exiting in one direction [19][20][21][22][23]. The distribution of heat transfer coefficient due to arrays of impinging jets involving an increase in spacing between the jets in the streamwise direction and an increase in jet-hole diameters in the streamwise direction using liquid crystal thermography was studied by Gao et al [24].…”

Section: Introductionmentioning

confidence: 99%

Influence of Spanwise Pitch on Local Heat Transfer for Multiple Jets with Crossflow

Katti

Prabhu

2008

Journal of Thermophysics and Heat Transfer

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The influence of spanwise jet-to-jet spacing on local heat transfer distribution due to multiple impinging circular air jets from an in-line rectangular array on a surface parallel to the jet plate is studied experimentally. The length-todiameter ratio of the nozzles of the jet plate is 1.0. The flow, after impingement, is constrained to exit in one direction from the confined passage formed between the jet plate and the target plate. Mean jet Reynolds numbers based on the nozzle-exit diameter d covered are 3000, 5000, 7500, and 10,000, and jet-to-plate spacings studied are d, 2d, and 3d. Spanwise pitches considered are 2d, 4d, and 6d, keeping the streamwise pitch at 5d. For all configurations, the jet plates have ten spanwise rows in the streamwise direction and six jets in each spanwise row. The flat heat transfer surface is made of thin stainless steel metal foil. Local temperature distribution on the target plate is measured using thermal infrared camera. Wall static pressure on the target plate is measured in the streamwise direction to estimate crossflow velocities and individual jet velocities. Heat transfer characteristics are explained on the basis of flow distribution. A simple correlation is developed to predict the streamwise distribution of the Nusselt number averaged over each spanwise strip resolved to one jet hole as a function of jet-flow and crossflow distributions.diameter of the jet, m G act = actual jet mass velocity based on jet-hole area, kg=s m 2 G c = channel crossflow mass velocity based on channel cross-sectional area, kg=s m 2 G ideal = theoretical jet mass velocity based on jet-hole area, kg=s m 2 G j = individual jet mass velocity based on jet-hole area, kg=s m 2 G j = mean jet mass velocity based on jet-hole area for the array, kg=s m 2 h = heat transfer coefficient, W=m 2 K k = thermal conductivity of the jet fluid, W=m K l=d = aspect ratio of the nozzle _ m j = mean mass flow rate from the nozzle, kg=s N c = number of streamwise rows of jets Nu = local Nusselt number (hd=k) Nu o;multijet = stagnation Nusselt number due to a jet in each spanwise row Nu o;single jet = stagnation Nusselt number due to a single jet estimated from the correlation corresponding to the jet-row Reynolds number Nu segment = Nusselt number averaged over each segment Nu strip = Nusselt number averaged over each spanwise strip resolved to one jet hole P = absolute static pressure at the nozzle exit, Pa P a = atmospheric pressure, Pa P o = absolute static pressure in the plenum or at the nozzle inlet, Pa Pr = Prandtl number Q = heater input power, W q 00 = net heat flux imposed on the target plate, W=m 2 R = characteristic gas constant of air, J=kg K Re = mean jet Reynolds number of flow exiting the nozzle (4 _ m j =d) Re j = individual spanwise-row jet Reynolds number T amb = ambient air temperature, K T j = reference jet fluid temperature on the target plate, K T o= plenum air temperature, K T w = target-plate surface temperature, K V j = mean jet velocity at the nozzle exit, m=s x = distance in the streamwi...

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“…The thermocouple technique can provide data at some discrete locations under consideration but does not allow for temperature measurement on the majority of the target surface. Later developments primarily used a transient liquid crystal thermography technique [3][4][5][6]. The transient liquid crystal technique provides very detailed local heat-transfer data but does not allow for time averaging of the convective heat-transfer coefficient; rather, it assumes that the convective heat-transfer coefficient is independent of time.…”

Section: Nomenclature Filmmentioning

confidence: 99%

Experimental Study of an Impingement Cooling-Jet Array Using an Infrared Thermography Technique

Schroder

Ou²,

Ghia

2012

Journal of Thermophysics and Heat Transfer

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An experimental test facility has been designed, constructed, and commissioned for studying the convective heat transfer of an array of 55 impingement jets with a constant heat-flux boundary condition. Spatial variation in timeaveraged Nusselt number as well as spanwise time-averaged Nusselt number are presented for jet Reynolds numbers of 4000, 8000, 12,000, and 15,000 for a jet-to-target standoff distance of z=D 3. For each of these configurations, the exit flow has also been varied to include both single-exit and double-exit configurations. The time and overall areaaveraged Nusselt number is presented as a function of jet Reynolds number. The results show that the time-averaged Nusselt number increases with increasing jet Reynolds number in both the local and spanwise-averaged values. The single-exit configuration provides lower values of local and spanwise-averaged Nusselt number for all jet Reynolds numbers studied compared with the double-exit configuration. This reduction is caused by more crossflow accumulation while it moves toward the exit. Nomenclature film = thermal diffusivity based upon film temperature, natural convection side, m 2 =s D = impingement-jet-nozzle diameter, m g = combined gravitational and centrifugal acceleration on the earth's surface, m=s 2 H = height of the imageable region of the foil heater, H hx; y; t = local impingement jet convective heat transfer coefficient, W=m 2 K I = current, A kx; y; t = local thermal conductivity based on the local film temperature, W=m K l = heated foil length, m N = total number of impingement jet nozzles Nux; y; t = local Nusselt number based on the jet nozzle diameter, hx; y; t D=kx; y; t Nu mean = time and area-averaged Nusselt number Nu natural x; y; t = Nusselt number for natural convection _ m = total mass flow rate through all impingement jet nozzles, kg=s q 00 foil = foil heater heat flux, W=m 2 q 00 losses x; y; t = heat losses on the imaged side of the foil, W=m 2 Ra y x; y; t = Rayleigh number, g T s;spanwise x; t T ambient y 3 = film;natural film;natural Re jet = Reynolds number based on the jet nozzle diameter T ambient = static temperature of the ambient air in the test cell, K T film x; y; t = local film temperature, T upstream T s x; y; t=2, K T s x; y; t = local foil surface temperature, K T s;spanwise x; t = spanwise-averaged surface temperature, 1=H R H 0 T s x; y; t dy, K T upstream = average fluid temperature measured in the pressure chamber, K t = time, s V = voltage drop across the foil heater, V w = heated foil width, m x = horizontal dimension, m y = vertical dimension, m z = normal dimension, m = expansion coefficient, (1=T s;spanwise x; t), 1=K = absolute viscosity, N s=m 2 film;natural= kinematic viscosity based upon film temperature, natural convection side, m 2 =s = ratio of the circumference of a circle to its diameter

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Flow and heat transfer of confined impingement jets cooling using a 3-D transient liquid crystal scheme

Cited by 46 publications

References 24 publications

Experimental and numerical investigation of impingement heat transfer on a flat and micro-rib roughened plate with different crossflow schemes

Experimental and numerical investigation of impingement heat transfer on a flat and micro-rib roughened plate with different crossflow schemes

Influence of Spanwise Pitch on Local Heat Transfer for Multiple Jets with Crossflow

Experimental Study of an Impingement Cooling-Jet Array Using an Infrared Thermography Technique

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