Air-side heat transfer characteristics of ambient air vaporizers with various geometric parameters under cryogenic frosting conditions

Al was sputtered onto four substrates: nylon, polyester, cotton/polyester, and shape memory polyurethane nanoweb, and the heat-transfer characteristics of the resultant materials were investigated by surface temperature measurements. The thickness of the Al layer increased linearly with sputtering time. The heat-transfer mechanisms of the multilayer systems in terms of conduction, convection, and radiation were investigated under steady-state conditions using a hot plate as a heat source in contact with Al-sputtered fabrics. The Al-sputtered fabric was placed on the hot plate, which was maintained at 35°C, and exposed to open air, which was maintained at 15°C. The temperatures of the air-facing surfaces of hot plate-Al-fabric-air (i.e., Al-phase-down) and hot plate-fabric-Al-air (i.e., Al-phase-up) systems were used to investigate the heat-transfer mechanism. It was found that heat dissipation to ambient air was much higher for the Al-phase-up system than for the Al-phase-down system. Heat-transfer coefficients of the Al surfaces were calculated and found to increase with the thickness of the Al layer. Furthermore, different conductive thermal resistances were observed for different fabrics prepared with the same Al-sputtering time. Consequently, differences in their thicknesses pore sizes, and thermal conductivities were suggested to have significant effects on their heat-transfer properties.

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Heat Transfer Characteristics for Inline and Staggered Arrays of Circular Jets with Crossflow of Spent Air

Journal of Heat Transfer ◽

10.1115/1.3451022 ◽

1979 ◽

Vol 101 (3) ◽

pp. 526-531 ◽

Cited By ~ 95

Author(s):

D. E. Metzger ◽

L. W. Florschuetz ◽

D. I. Takeuchi ◽

R. D. Behee ◽

R. A. Berry

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Heat Transfer Surface ◽

Geometric Parameters ◽

Channel Height ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Nusselt Numbers ◽

Circular Jets ◽

Impinging Flow

Heat transfer characteristics were measured for two-dimensional arrays of jets impinging on a surface parallel to the jet orifice plate. The impinging flow was constrained to exit in a single direction along the channel formed by the jet plate and the heat transfer surface. Both mean Nusselt numbers and streamwise Nusselt number profiles are presented as a function of Reynolds number and geometric parameters. The results show that significant periodic variations occur in the streamwise Nusselt number profiles, persisting downstream for at least ten rows of jet holes. Both channel height and hole spacing can have a significant effect on the streamwise profiles, smoothed across the periodic variations. Where significant differences exist, inline hole patterns provide better heat transfer than staggered ones, particularly downstream. These and other effects of the geometric parameters are presented and discussed.

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Experimental Investigation on Impingement Heat Transfer From Rib Roughened Surface Within Arrays of Circular Jet: Effect of Geometric Parameters

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/98-gt-208 ◽

1998 ◽

Cited By ~ 9

Author(s):

Chang Haiping ◽

Zhang Jingyu ◽

Huang Taiping

Keyword(s):

Heat Transfer ◽

Flux Ratio ◽

Hole Diameter ◽

Geometric Parameters ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Impingement Heat Transfer ◽

Roughened Surface ◽

Turbine Airfoils ◽

Rib Roughened

Impingement heat transfer from rib roughened surface within two-dimensional arrays of circular jet with initial crossflow has been investigated experimentally. The configurations considered are intended to simulate the impingement cooled midchord region of the gas turbine airfoils in case where an initial crossflow is present. Many factors affect the heat transfer. The relative positions of the jet hole to the ribs and the geometric parameters have the significant effect on the heat transfer characteristics and have been experimentally studied. The investigation on the effect of the relative position of the jet hole to the ribs has been presented in an other paper. The effects of the geometric parameters such as jet hole spacing, jet-to-surface spacing, rib pitch-to-height ratio and rib height-to-hole diameter ratio on the heat transfer characteristics are considered in this paper. The experimentation is conducted under the conditions of Reynolds number 7,000–15,000 and the crossflow-to-jet mass flux ratio based on each channel/jet hole area 0∼0.5. With three jet hole spacing to jet hole diameter ratios, five jet-to-surface spacings, three rib pitch-to-height ratios and three rib height-to-hole diameter ratios, a great number of experimental data has been obtained. Based on this, the effects of the geometric parameters on the heat transfer characteristics have been obtained qualitatively and quantitatively. It can be used for evaluating the efficiency of the impingement heat transfer.

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Inaccuracy of Heat Transfer Characteristics of a Metal Duct Neglecting Heat Radiation Effect in Ambient Air

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.516-517.322 ◽

2012 ◽

Vol 516-517 ◽

pp. 322-327 ◽

Cited By ~ 1

Author(s):

King Leung Wong ◽

Wen Lih Chen ◽

Yung Chin Chiu

Keyword(s):

Heat Transfer ◽

Temperature Difference ◽

Radiation Effect ◽

Ambient Air ◽

Heat Radiation ◽

Heat Transfer Characteristics ◽

Circular Duct ◽

Transfer Characteristics ◽

Internal Fluid ◽

Fluid Convection

A heat radiation equation contains 4th exponential order of temperature which makes mathematics analysis complicated and time-consumption. Most heat transfer experts and scholars believe, based on their own experiences, that the heat radiation effect can be ignored in situations of small temperature difference between duct surfaces and surroundings. This paper studies in detail for complete heat transfer characteristics of a circular duct with heat radiation effect taken into account. It is found that, in some practical conditions, the heat radiation effect can not be ignored especially in cases of lower ambient convection heat coefficients and larger surface emissivities, as well as the smaller the duct size and/or the greater the duct conductivity and/or internal fluid convection coefficients, even though the temperature-difference between inner and outer fluid-temperatures of duct is low to 1 °C. It is found that the conventional LMTD method (ignoring heat radiation) cannot be applied to calculate the total heat transfer rate of a single-duct heat exchanger located in ambient air, such as condenser and evaporator.

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Flow and Heat Transfer Characteristics of Impinging Jet from Expansion Pipe Nozzle with Air Entrainment Holes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.931-932.1213 ◽

2014 ◽

Vol 931-932 ◽

pp. 1213-1217 ◽

Cited By ~ 1

Author(s):

Natthaporn Kaewchoothong ◽

Makatar Wae-Hayee ◽

Passakorn Vessakosol ◽

Banyat Niyomwas ◽

Chayut Nuntadusit

Keyword(s):

Heat Transfer ◽

Infrared Camera ◽

Air Entrainment ◽

Impinging Jet ◽

Ambient Air ◽

Jet Flow ◽

Heat Transfer Characteristics ◽

Pipe Length ◽

Transfer Characteristics ◽

Flow And Heat Transfer

Flow and heat transfer characteristics of impinging jet from expansion pipe were experimentally and numerically investigated. The expansion pipe nozzle was drilled on expansion wall for increasing an entrainment of ambient air into a jet flow. The diameter of round pipe nozzle was d=17.2 mm and the diameter of expansion pipe was fixed at D=68.8 mm (=4d). The number of air entrainment holes was varied at 4, 6 and 8 holes, and the expansion pipe length was examined at L= 2d, 4d and 6d. In this study, the expansion pipe exit-to-plate distance was fixed at H=2d and the Reynolds number of jet was studied at Re=20,000. Temperature distribution on the impinged surface was acquired by using an infrared camera. The numerical simulation was carried out to reveal the flow field. The results show that the ambient air enters through the holes and subsequently blocked the entrainment of ambient air into the jet flow. It causes to enhance the heat transfer particularly at stagnation point higher than the case of conventional pipe: 4.68% for 4 holes at L=2d, 6.4% and 6.28% for 4 holes and without holes at L=4d and 5.48% for 8 holes at L=6d.

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The effect of the geometric parameters of a perforated plate on its heat transfer characteristics

Cryogenics ◽

10.1016/0011-2275(95)00170-0 ◽

1996 ◽

Vol 36 (6) ◽

pp. 443-446 ◽

Cited By ~ 7

Author(s):

Guo Tingwei ◽

Zhu Tingying ◽

Hu Jichuan ◽

Gong Linghui

Keyword(s):

Heat Transfer ◽

Perforated Plate ◽

Geometric Parameters ◽

Heat Transfer Characteristics ◽

Transfer Characteristics

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Effect of Helical Vane Swirler Geometry on Heat Transfer Characteristics for Compressed Natural Gas/Air Swirling Flame Impinging on a Flat Surface

Volume 8A: Heat Transfer and Thermal Engineering ◽

10.1115/imece2013-63968 ◽

2013 ◽

Cited By ~ 1

Author(s):

Subhash Chander ◽

Gurpreet Singh

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Natural Gas ◽

Flat Surface ◽

Geometric Parameters ◽

Heat Transfer Characteristics ◽

Compressed Natural Gas ◽

Transfer Characteristics ◽

Swirl Intensity ◽

Swirling Flame

An experimental study has been conducted to investigate the effect of helical vane swirler geometry on heat transfer characteristics for compressed natural gas (CNG)/air swirling flame impinging on a flat surface. Effects of helical vane swirler geometric parameters like, length of helical insert (25 mm, 45 mm and 65 mm), depth of groove on the helical insert (2.5 mm, 3.5 mm and 4.5 mm) and number of helical vanes (8, 10 and 12), on heat transfer characteristics have been studied. All the inserts were having fixed helical vane angle of 45°. Also, the burner exit diameter was kept constant (d = 20 mm). Experiments were conducted at different dimensionless separation distances (6, 4, 3 and 2) for fixed values of Reynolds number (6000) and equivalence ratio (1.3). Significant variation in the heat flux profiles has been observed for different swirler inserts till the radial hump in heat flux. After the radial hump, almost in all cases, the heat flux lines merged together. These variations in the heat flux profiles were due to different level of swirling intensities produced by different swirlers at fixed value of the helical vane swirler angle. It was observed that the heating was comparatively more uniform at larger separation distances (H/d = 6). It has been concluded that defining swirl intensity only with the helical vane swirler angle would be incorrect for such type of swirlers. Other geometric parameters of the swirler like, number of vanes, length of the swirler and the depth of the groove should also be included in swirl intensity definition.

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