Transient Heat Transfer Analysis of Freeze Plate Structures Cooled by Nanofluids

2006 ◽  
Author(s):  
Rong-Yuan Jou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Nano Particles ◽  
Heat Transfer Analysis ◽  
Transient Heat Transfer ◽  
Innovative Technology ◽  
Transfer Enhancement ◽  
Left Hand ◽  
Smooth Channel ◽  
Transport Problems

Heat transfer enhancement by nanofluids is an emerging and innovative technology for traditional heat transfer problems. However, researches of nanofluids for refrigeration applications are rare either theoretically or experimentally. In this paper, the physical model of a freezing chucker is considered as a two-dimensional domain which is consist of the top and bottom copper plates, and a channel for flowing of copper nanofluids. Inlet flow passes through the left hand side and exhausts to the outlet at right hand side. Three kinds of transverse rib structures, e/Dh = 0.1, 0.2, 0.3, are attached on the internal top wall of the channel for heat transfer enhancement of the coolant flows. To investigate this problem, the transient heat transfer of this channel flow is analyzed and transport problems are solved numerically for the ethylene-glycol (EG) based nanofluids mixture of copper nano-particles with volume fractions of 0%, 0.5%, 1%, 5%, respectively. The smooth channel problem is analyzed and compared to the ribbed channel problem. Analyses of the highest decay rate, the lowest temperature, and temperature distributions of the top-plate surface of a freezing chucker are shown.

Heat Transfer Enhancement Using a Convex-Patterned Surface

2003 ◽  
Vol 125 (2) ◽  
pp. 274-280 ◽  
Author(s):  
H. K. Moon ◽  
T. O’Connell ◽  
R. Sharma
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Reynolds Numbers ◽  
Smooth Wall ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Patterned Surface ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Smooth Channel

The heat transfer rate from a smooth wall in an internal cooling passage can be significantly enhanced by using a convex patterned surface on the opposite wall of the passage. This design is particularly effective for a design that requires the heat transfer surface to be free of any augmenting features (smooth). Heat transfer coefficients on the smooth wall in a rectangular channel, which had convexities on the opposite wall were experimentally investigated. Friction factors were also measured to assess the thermal performance. Relative clearances δ/d between the convexities and the smooth wall of 0, 0.024, and 0.055 were investigated in a Reynolds number ReHD range from 15,000 to 35,000. The heat transfer coefficients were measured in the thermally developed region using a transient thermochromic liquid crystal technique. The clearance gap between the convexities and the smooth wall adversely affected the heat transfer enhancement NuHD. The friction factors (f ), measured in the aerodynamically developed region, were largest for the cases of no clearance δ/d=0). The average heat transfer enhancement Nu¯HD was also largest for the cases of no clearance δ/d=0, as high as 3.08 times at a Reynolds number of 11,456 in relative to that Nuo of an entirely smooth channel. The normalized Nusselt numbers Nu¯HD/Nuo, as well as the normalized friction factors f/fo, for all three cases, decreased with Reynolds numbers. However, the decay rate of the friction factor ratios f/fo with Reynolds numbers was lower than that of the normalized Nusselt numbers. For all three cases investigated, the thermal performance Nu¯HD/Nuo/f/fo1/3 values were within 5% to each other. The heat transfer enhancement using a convex patterned surface was thermally more effective at a relative low Reynolds numbers (less than 20,000 for δ/d=0) than that of a smooth channel.

Effect of 45-Deg Rib Orientations on Heat Transfer in a Rotating Two-Pass Channel With Aspect Ratio From 4:1 to 2:1

2019 ◽  
Author(s):  
Izzet Sahin ◽  
Andrew F. Chen ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Rotation Number ◽  
Pressure Loss ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
First Passage

Abstract The internal cooling passages of gas turbine blades mostly have varying aspect ratios from one passage to another. However, there are limited data available in the open literature that used a reduced cross-section and aspect ratio, AR, after the tip turn. Therefore, the current study presents heat transfer and pressure drop of three different α = 45° profiled rib orientations, typical parallel (usual), reversed parallel (unusual), and criss-cross patterns in a rotating two-pass rectangular channel with AR = 4:1 and 2:1 in the first radially outward flow and second radially inward flow passages respectively. For each rib orientation, regional averaged heat transfer results are obtained for both the flow passages with the Reynolds number ranging from 10,000 to 70,000 for the first passage and 16000 to 114000 for the second passage with a rotational speed range of 0 rpm to 400 rpm. This results in the highest rotation number of 0.39 and 0.16 for the first and second passage respectively. The effects of rib orientation, aspect ratio variation, 180° tip turn, and rotation number on the heat transfer and pressure drop will be addressed. According to the results, for usual, unusual and criss-cross rib patterns, increasing rotation number causes the heat transfer to decrease on the leading surface and increase on the trailing surface for the first passage and vice versa for the second passage. Overall heat transfer enhancement of the usual and unusual rib patterns is higher than criss-cross one. In terms of the pressure losses, the criss-cross rib pattern has the lowest and the usual rib pattern has the highest-pressure loss coefficients. When pressure loss and heat transfer enhancement are both taken into account together, the criss-cross or unusual rib pattern might be an option to use in the internal cooling method. Therefore, the results can be useful for turbine blade internal cooling design and heat transfer analysis.

Heat Transfer Enhancement Induced by Cube- and Diamond-Shaped Block Arrays in Two-Pass High-Aspect Ratio Channels With a 180-Degree Turn

2010 ◽  
Author(s):  
Pavin Ganmol ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
High Aspect Ratio ◽  
Local Heat Transfer ◽  
Channel Height ◽  
Transfer Enhancement ◽  
Smooth Channel ◽  
Sharp Turn ◽  
First Pass

Described in this paper is an experimental investigation of the heat transfer and pressure characteristics in a high aspect ratio, (4.5:1 width-to-height), two-pass channel, with cube-shaped and diamond-shaped block arrays placed in both passes before and after a 180-degree sharp turn. Transient liquid crystal technique was applied to acquire detailed local heat transfer data on both the channel surfaces and the block elements. Reynolds number tested varies between 13000 and 28000. To further explore potential design alternatives for enhancement cooling, the effects of block height, ranging from 1/4, 1/2, 3/4 and full span of the channel height were also evaluated. Present results suggest that a staggered cube-array can enhance heat transfer rate up to 3.5 fold in the first pass and about 1.9 fold in the second pass, relative to the fully-developed smooth channel counterpart. For the corresponding diamond-shaped block array, the enhancement is 3.4 and 1.9 fold respectively. Even though the post-turn turbulence transport in the second pass is generally higher than that in the first pass, the effects of surface-block induced heat transfer enhancement in fact are less prominent in the post-turn region of the second pass. Pressure loss for diamond block arrays is generally higher than that of the corresponding cube-block arrays.

Effect of 45-deg Rib Orientations on Heat Transfer in a Rotating Two-Pass Channel With Aspect Ratio from 4:1 to 2:1

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Izzet Sahin ◽  
Andrew F Chen ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Rotation Number ◽  
Pressure Loss ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
First Passage

Abstract The internal cooling passages of gas turbine blades mostly have varying aspect ratios from one passage to another. However, there are limited data available in the open literature that used a reduced cross section and aspect ratio (AR), after the tip turn. Therefore, the current study presents heat transfer and pressure drop of three different α = 45 deg profiled rib orientations, typical parallel (usual), reversed parallel (unusual), and crisscross patterns in a rotating two-pass rectangular channel with AR = 4:1 and 2:1 in the first radially outward flow and second radially inward flow passages, respectively. For each rib orientation, regional averaged heat transfer results are obtained for both the flow passages with the Reynolds number ranging from 10,000 to 70,000 for the first passage and 16,000 to 114,000 for the second passage with a rotational speed range of 0–400 rpm. This results in the highest rotation number of 0.39 and 0.16 for the first and second passage respectively. The effects of rib orientation, aspect ratio variation, 180-deg tip turn, and rotation number on the heat transfer and pressure drop will be addressed. According to the results, for usual, unusual and crisscross rib patterns, increasing rotation number causes the heat transfer to decrease on the leading surface and increase on the trailing surface for the first passage and vice versa for the second passage. The overall heat transfer enhancement of the usual and unusual rib patterns is higher than the crisscross one. In terms of the pressure losses, the crisscross rib pattern has the lowest and the usual rib pattern has the highest-pressure loss coefficients. When pressure loss and heat transfer enhancement are both taken into account together, the crisscross or unusual rib pattern might be an option to use in the internal cooling method. Therefore, the results can be useful for the turbine blade internal cooling design and heat transfer analysis.

Dimple Enhanced Heat Transfer in High Aspect Ratio Channels

2001 ◽  
Author(s):  
Srinath V. Ekkad ◽  
Hasan Nasir
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Rectangular Cross Section ◽  
Rectangular Channel ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
High Heat Transfer ◽  
Smooth Channel ◽  
Wide Range

Abstract Detailed heat transfer measurements are presented for a rectangular channel with dimples on one wall. Dimpled surfaces provide high heat transfer enhancement comparable to ribbed surfaces with reduced overall pressure drop. The heat transfer coefficients were measured using a transient liquid crystal technique. The effect of channel flow Reynolds number was investigated for a wide range from 10000 to 65000. The channel is a 25.4 mm × 101.6 mm (1” × 4”) rectangular cross-section with the dimples on one of the 101.6 mm wall. Heat transfer enhancement around three times that of a smooth channel were achieved for all flow conditions. The overall pressure drop through the dimpled section of the passage was also measured. The resulting thermal performance of the dimples surfaces is significantly higher compared to channels with protruding ribs.

Numerical Simulation of Laminar Flow Heat Transfer Enhancement Using Surface Modification

2014 ◽  
Author(s):  
Abhijit S. Paranjape ◽  
Ninad C. Maniar ◽  
Deval A. Pandya ◽  
Brian H. Dennis
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Surface Modification ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Longitudinal Vortex ◽  
Bottom Wall ◽  
Transfer Enhancement ◽  
Smooth Channel

Heat transfer augmentation techniques have gained great importance in different engineering applications to deal with thermal management issues. In this work, a numerical investigation was carried out to see the effects of a modified surface on the heat transfer enhancement compared to a smooth surface. In the first case, spherical dimple arrays were applied to the surface. The effects were observed for dimples on the bottom wall of a channel for a laminar airflow. The effects of a 21×7 staggered array and a 19×4 inline array on the bottom wall were investigated. In the second case, the heat exchange enhancement in a rectangular channel using longitudinal vortex generators (LVG) for a laminar flow was considered. In both cases, a 3D steady viscous computational fluid dynamics package with an unstructured grid was used to compute the flow and temperature field. The heat transfer characteristics were studied as a function of the Reynolds number based on the hydraulic diameter of the channel. The heat transfer was quantified by computing the surface averaged Nusselt number. The pressure drop and flow characteristics were also calculated. The Nusselt number was compared with that of a smooth channel without surface modification to assess the level of heat transfer enhancement.

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