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THE EFFECT OF HEAT TRANSFER COEFFICIENT ON HIGH ASPECT RATIO CHANNEL ACCOMPANIED BY VARYING RIB ASPECT RATIO
Title
THE EFFECT OF HEAT TRANSFER COEFFICIENT ON HIGH ASPECT RATIO CHANNEL ACCOMPANIED BY VARYING RIB ASPECT RATIO.
Creator
Le, An, Kapat, Jayanta, University of Central Florida
Abstract / Description
Heat transfer and pressure data were performed and reported on two different rigs. The first rig has an aspect ratio of (19:1) with two different inlet conditions and the second rig is composed of two different aspect ratio channels, (1:8) and (1:4). Rib turbulators were used as a flow disruptor scheme to enhance the heat transfer and friction factor. Rib aspect ratios ranging from (1:1) to (1:5) rib-height-to-width ratio were used. The first channel rib-width-to-pitch (Wr/P) ratio was kept...
Show moreHeat transfer and pressure data were performed and reported on two different rigs. The first rig has an aspect ratio of (19:1) with two different inlet conditions and the second rig is composed of two different aspect ratio channels, (1:8) and (1:4). Rib turbulators were used as a flow disruptor scheme to enhance the heat transfer and friction factor. Rib aspect ratios ranging from (1:1) to (1:5) rib-height-to-width ratio were used. The first channel rib-width-to-pitch (Wr/P) ratio was kept at 1/2 where flow was kept at relatively low Reynolds numbers, between 3000 and 13000. Results from the current tests showed that existing correlations could be used for high aspect ratio channels in predicting the effectiveness of the cooling scheme. Two different inlet conditions were tested; one was arranged so that the flow was hydrodynamically fully-developed at the entrance of the heated section, while the other uses an abrupt entrance from bleeding off mass flow from a horizontal channel. The heat transfer augmentation (compared to a well known and accepted correlation proposed by Dittus-Boelter) in these channels are extremely high with an average of 350% to 400%. However, this was accompanied by a substantial increase in the pressure drop, causing the overall thermal performance to increase between twenty to thirty percent. The second channel rib-width-to-pitch ratio (Wr/P) ranges from 0.1, 0.3, and 0.5; the flow conditions are tested from 20,000 to 40,000 Reynolds number. Correlations for heat transfer and friction augmentation of the test data was also given. The test shows large rib blockage ratio does not demonstrate the best thermal performance; however it does give a high heat transfer augmentation ranging from 200 to 300 percent for both aspect ratios depending on the width of the used ribs.
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Date Issued
2009
Identifier
CFE0002782, ucf:48130
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002782
EFFECT OF RIB ASPECT RATIO ON HEAT TRANSFER AND FRICTION IN RECTANGULAR CHANNELS
Title
EFFECT OF RIB ASPECT RATIO ON HEAT TRANSFER AND FRICTION IN RECTANGULAR CHANNELS.
Creator
Tran, Lucky, kapat, Jay, University of Central Florida
Abstract / Description
The heat transfer and friction augmentation in the fully developed portion of a 2:1 aspect ratio rectangular channel with orthogonal ribs at channel Reynolds numbers of 20,000, 30,000, and 40,000 is studied both experimentally and computationally. Ribs are applied to the two opposite wide walls. The rib aspect ratio is varied systematically at 1, 3, and 5, with a constant rib height and constant rib pitch (rib-pitch-to-rib-height ratio of 10). The purpose of the study is to extend the...
Show moreThe heat transfer and friction augmentation in the fully developed portion of a 2:1 aspect ratio rectangular channel with orthogonal ribs at channel Reynolds numbers of 20,000, 30,000, and 40,000 is studied both experimentally and computationally. Ribs are applied to the two opposite wide walls. The rib aspect ratio is varied systematically at 1, 3, and 5, with a constant rib height and constant rib pitch (rib-pitch-to-rib-height ratio of 10). The purpose of the study is to extend the knowledge of the performance of rectangular channels with ribs to include high aspect ratio ribs. The experimental investigation is performed using transient Thermochromic Liquid Crystals technique to measure the distribution of the local Nusselt numbers on the ribbed walls. Overall channel pressure drop and friction factor augmentation is also obtained with the experimental setup. A numerical simulation is also performed by solving the 3-D Reynolds-averaged Navier-Stokes equations using the realizable-k-[episilon] turbulence model for closure. Flow visualization is obtained from the computational results as well as numerical predictions of local distributions of Nusselt numbers and overal channel pressure drop. Results indicate that with increasing rib width, the heat transfer augmentation of the ribbed walls decreases with a corresponding reduction in channel pressure drop.
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Date Issued
2011
Identifier
CFH0004103, ucf:44890
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004103
Analysis of Heat Transfer on Turbulence Generating Ribs using Dynamic Mode Decomposition
Title
Analysis of Heat Transfer on Turbulence Generating Ribs using Dynamic Mode Decomposition.
Creator
Elmore, Michael, Kapat, Jayanta, Ahmed, Kareem, Bhattacharya, Samik, University of Central Florida
Abstract / Description
Ducts with turbulence-promoting ribs are common in heat transfer applications. This study usesa recent modal extraction technique called Dynamic Mode Decomposition (DMD) to determinemode shapes of the spatially and temporally complex flowfield inside a ribbed duct. One subjectmissing from current literature is a method of directly linking a mode to a certain engineeringquantity of interest. Presented is a generalized methodology for producing such a link utilizing thedata from the DMD...
Show moreDucts with turbulence-promoting ribs are common in heat transfer applications. This study usesa recent modal extraction technique called Dynamic Mode Decomposition (DMD) to determinemode shapes of the spatially and temporally complex flowfield inside a ribbed duct. One subjectmissing from current literature is a method of directly linking a mode to a certain engineeringquantity of interest. Presented is a generalized methodology for producing such a link utilizing thedata from the DMD analysis. Theory suggests exciting the modes which are identified may causethe flow to change in such a way to promote the quantity of interest, in this case, heat transfer. Thistheory is tested by contouring the walls of the duct by the extracted mode shapes.The test procedure is taken from an industrial perspective. An initial, unmodified geometry pro-vides a baseline for comparison to later contoured models. The initial case is run as a steady-stateReynolds-Averaged Navier-Stokes model. Large-Eddy Simulation generates the necessary datafor the DMD analysis. Several mode shapes extracted from the flow are applied to the duct wallsand run again in the RANS model, then compared to the baseline, and their relative performanceexamined.
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Date Issued
2018
Identifier
CFE0007328, ucf:52123
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007328