scholarly journals Heat transfer enhancement at evaporation and boiling of liquid on capillary-porous surfaces created by 3D printing

2021 ◽  
Vol 2119 (1) ◽  
pp. 012075
Author(s):  
O A Volodin ◽  
N I Pecherkin ◽  
A N Pavlenko
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
3D Printing ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Fold Increase ◽  
Transfer Enhancement ◽  
Enhance Heat Transfer ◽  
Porous Copper ◽  
Boiling Heat Transfer Coefficient

Abstract The paper presents the results of experiments on measuring heat transfer in laminar-wave films of R114/R21 refrigerant mixture flowing down a vertical plate (70 × 80 mm). The experiments were carried out on the saturation line at a pressure of 2 bar. To enhance heat transfer, a porous copper coating with a flat layer thickness of 400 μm and a porosity of 45% was applied to the heat-transfer surface by 3D printing. The effectiveness of the application of the technique used for the heat transfer enhancement is demonstrated: an increase in the boiling heat transfer coefficient is obtained up to three times in comparison with the reference smooth surface, as well as two-fold increase in heat transfer coefficient in the evaporation regime. Based on the obtained experimental results and analysis of the research data of other authors, the geometric structure of promising multiscale porous enhancing coating is proposed for further research.

An Experimental Investigation of Structured Roughness Effect on Heat Transfer During Single-Phase Liquid Flow at Microscale

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Ting-Yu Lin ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Enhancement Factor ◽  
Roughness Element ◽  
Hydraulic Diameter ◽  
Transfer Enhancement ◽  
Roughness Elements ◽  
The Heat Transfer Coefficient

The effect of structured roughness on the heat transfer of water flowing through minichannels was experimentally investigated in this study. The test channels were formed by two 12.7 mm wide × 94.6 mm long stainless steel strips. Eight structured roughness elements were generated using a wire electrical discharge machining (EDM) process as lateral grooves of sinusoidal profile on the channel walls. The height of the roughness structures ranged from 18 μm to 96 μm, and the pitch was varied from 250 μm to 400 μm. The hydraulic diameter of the rectangular flow channels ranged from 0.71 mm to 1.87 mm, while the constricted hydraulic diameter (obtained by using the narrowest flow gap) ranged from 0.68 mm to 1.76 mm. After accounting for heat losses from the edges and end sections, the heat transfer coefficient for smooth channels was found to be in good agreement with the conventional correlations in the laminar entry region as well as in the laminar fully developed region. All roughness elements were found to enhance the heat transfer. In the ranges of parameters tested, the roughness element pitch was found to have almost no effect, while the heat transfer coefficient was significantly enhanced by increasing the roughness element height. An earlier transition from laminar to turbulent flow was observed with increasing relative roughness (ratio of roughness height to hydraulic diameter). For the roughness element designated as B-1 with a pitch of 250 μm, roughness height of 96 μm and a constricted hydraulic diameter of 690 μm, a maximum heat transfer enhancement of 377% was obtained, while the corresponding friction factor increase was 371% in the laminar fully developed region. Comparing different enhancement techniques reported in the literature, the highest roughness element tested in the present work resulted in the highest thermal performance factor, defined as the ratio of heat transfer enhancement factor (over smooth channels) and the corresponding friction enhancement factor to the power 1/3.

Phase Change Material Particulate Flow Through a Rectangular Channel: Effect of Parachute-Shaped Particles on the Heat Transfer

2011 ◽  
Author(s):  
Laura Small ◽  
Fatemeh Hassanipour
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Phase Change Material ◽  
Volume Fraction ◽  
Particulate Flow ◽  
Transfer Enhancement ◽  
Change Material

This study presents numerical simulations of forced convection with parachute-shaped encapsulated phase-change material particles in water, flowing through a square cross-section duct with top and bottom iso-flux surfaces. The system is inspired by the gas exchange process in the alveolar capillaries between the red blood cells (RBC) and the lung tissue. The numerical model was developed for the motion of elongated encapsulated phase change particles along a channel in a particulate flow where particle diameters are comparable with the channel height. Results of the heat transfer enhancement for the parachute-shaped particles are compared with the circular particles. Results reveal that the key role in heat transfer enhancement is the snugness movement of the particles and the parachute-shaped geometry yields small changes in heat transfer coefficient when compared to the circular ones. The effects of various parameters including particle diameter and volume-fraction, as well as fluid speed, on the heat transfer coefficient is investigated and reported in this paper.

Experimental Study of Advanced Convective Cooling Techniques for Combustor Liners

2008 ◽  
Author(s):  
Michael Maurer ◽  
Uwe Ruedel ◽  
Michael Gritsch ◽  
Jens von Wolfersdorf
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Transfer Enhancement ◽  
Number Range ◽  
Convective Cooling

An experimental study was conducted to determine the heat transfer performance of advanced convective cooling techniques at the typical conditions found in a backside cooled combustion chamber. For these internal cooling channels, the Reynolds number is usually found to be above the Reynolds number range covered by available databases in the open literature. As possible candidates for an improved convective cooling configuration in terms of heat transfer augmentation and acceptable pressure drops, W-shaped and WW-shaped ribs were considered for channels with a rectangular cross section. Additionally, uniformly distributed hemispheres were investigated. Here, four different roughness spacings were studied to identify the influence on friction factors and the heat transfer enhancement. The ribs and the hemispheres were placed on one channel wall only. Pressure losses and heat transfer enhancement data for all test cases are reported. To resolve the heat transfer coefficient, a transient thermocromic liquid crystal technique was applied. Additionally, the area-averaged heat transfer coefficient on the W-shaped rib itself was observed using the so-called lumped-heat capacitance method. To gain insight into the flow field and to reveal the important flow field structures, numerical computations were conducted with the commercial code FLUENT™.

Condensation Pressure Drop and Heat Transfer in 5-mm-OD Micro-Fin Tubes

2012 ◽  
Author(s):  
Wei Li ◽  
Dan Huang ◽  
Zan Wu ◽  
Hong-Xia Li ◽  
Zhao-Yan Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Condensation Heat Transfer ◽  
Transfer Enhancement ◽  
Mass Fluxes ◽  
Fin Tubes ◽  
Condensation Heat Transfer Coefficient

An experimental investigation was performed for convective condensation of R410A inside four micro-fin tubes with the same outside diameter (OD) 5 mm and helix angle 18°. Data are for mass fluxes ranging from about 180 to 650 kg/m2s. The nominal saturation temperature is 320 K, with inlet and outlet qualities of 0.8 and 0.1, respectively. The results suggest that Tube 4 has the best thermal performance for its largest condensation heat transfer coefficient and relatively low pressure drop penalty. Condensation heat transfer coefficient decreases at first and then increases or flattens out gradually as G decreases. This complex mass-flux effect may be explained by the complex interactions between micro-fins and fluid. The heat transfer enhancement mechanism is mainly due to the surface area increase over the plain tube at large mass fluxes, while liquid drainage and interfacial turbulence play important roles in heat transfer enhancement at low mass fluxes. In addition, the experimental data was analyzed using seven existing pressure-drop and four heat-transfer models to verify their respective accuracies.

scholarly journals Quantitative Evaluation of the Dependence of Pool Boiling Heat Transfer Enhancement on Sintered Particle Coating Characteristics

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Suchismita Sarangi ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Transfer Enhancement ◽  
Pool Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient ◽  
Coating Characteristics

Immersion cooling strategies often employ surface enhancements to improve the pool boiling heat transfer performance. Sintered particle/powder coatings have been commonly used on smooth surfaces to reduce the wall superheat and increase the critical heat flux (CHF). However, there is no unified understanding of the role of coating characteristics on pool boiling heat transfer enhancement. The morphology and size of the particles affect the pore geometry, permeability, thermal conductivity, and other characteristics of the sintered coating. In turn, these characteristics impact the heat transfer coefficient and CHF during boiling. In this study, pool boiling of FC-72 is experimentally investigated using copper surfaces coated with a layer of sintered copper particles of irregular and spherical morphologies for a range of porosities (∼40–80%). Particles of the same effective diameter (90–106 μm) are sintered to yield identical coating thicknesses (∼4 particle diameters). The porous structure formed by sintering is characterized using microcomputed tomography (μ-CT) scanning to study the geometric and effective thermophysical properties of the coatings. The boiling performance of the porous coatings is analyzed. Coating characteristics that influence the boiling heat transfer coefficient and CHF are identified and their relative strength of dependence analyzed using regression analysis. Irregular particles yield higher heat transfer coefficients compared to spherical particles at similar porosity. The coating porosity, pore diameter, unit necking area, unit interfacial area, effective thermal conductivity, and effective permeability are observed to be the most critical coating properties affecting the boiling heat transfer coefficient and CHF.

Applied Pulsed Flow for Single-Phase Convective Heat Transfer Enhancement in a Laminar Flow Cooling System

2008 ◽  
Author(s):  
Bolaji O. Olayiwola ◽  
Gerhard Schaldach ◽  
Peter Walzel
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Cooling System ◽  
Transfer Enhancement ◽  
Flow Rates ◽  
The Heat Transfer Coefficient

Experimental and CFD studies were performed to investigate the enhancement of convective heat transfer in a laminar cooling system using flow pulsation in a flat channel with series of regular spaced fins. Glycerol-water mixtures with dynamic viscosities in the range of 0.001 kg/ms–0.01 kg/ms were used. A steady flow Reynolds number in the laminar range of 10 < Re < 1200 was studied. The amplitudes of the applied pulsations are in the range of 0.25 < A < 0.55 mm and the frequency range is 10 < f < 60 Hz. Two different cooling devices with active length L = 450 mm and 900 mm were investigated. CFD simulations were performed on a parallel-computer (Linux-cluster) using the software suit CFX11 from ANSYS GmbH, Germany. The rate of cooling was found to be significant at moderate low net flow rates. In general, no significant heat transfer enhancement at very low and high flow rates was obtained in compliance with the experimental data. The heat transfer coefficient was found to increase with increasing Prandtl number Pr at constant oscillation Reynolds number Reosc whereas the ratio of the hydraulic diameter to the length of the channel dh/L has insignificant effect on the heat transfer coefficient. This is due to enhanced fluid mixing. CFD results allow for performance predictions of different geometries and flow conditions.

Effect of Heat Flux on Pool Boiling Heat Transfer Enhancement (Numerical Investigation Approach)

2020 ◽  
Author(s):  
T. S. Mogaji ◽  
O. A. Sogbesan ◽  
Tien-Chien Jen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Numerical Investigation ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Transfer Enhancement

Abstract This study presents numerical investigation results of heat flux effect on pool boiling heat transfer enhancement during nucleate boiling heat transfer of water. The simulation was performed for five different heated surfaces such as: brass, copper, mild steel, stainless steel and aluminum using ANSYS simulation software at 1 atmospheric pressure. The samples were heated in a domain developed for bubble growth during nucleate boiling process under the same operational condition of applied heat flux ranged from 100 to 1000 kW/m2 and their corresponding heat transfer coefficient was obtained numerically. Obtained experimental data of other authors from the open literature result is in close agreement with the simulated data, thus confirming the validity of the CFD simulation method used in this study. It is found that heat transfer coefficient increases with increasing heat flux. The results revealed that in comparison to other materials tested, better heat transfer performance up to 38.5% and 7.11% is observed for aluminum and brass at lower superheated temperature difference conditions of 6.96K and 14.01K respectively. This behavior indicates better bubble development and detachment capability of these heating surface materials and could be used in improving the performance of thermal devices toward producing compact and miniaturized equipment.

Investigation on the Multiple Jet Impingement Heat Transfer Using Al2O3-Water Nanofluid

2013 ◽  
Author(s):  
Caner Senkal ◽  
Shuichi Torii
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Heat Dissipation ◽  
Jet Impingement ◽  
High Heat ◽  
Experimental Results ◽  
Transfer Enhancement ◽  
Particle Volume

In recent years, increasing demands for high performance electronic devices give rise to a necessity to remove enormous amount of heat fluxes from small areas. Uniform temperature distribution and sufficient heat transfer dissipation are crucial issues for proper operation of electronic components. To cope up with thermal management of high heat dissipation devices, an efficient cooling method is required. Jet impingement cooling is one of those promising candidates which can handle heat dissipation in an effective way due to its superior heat transfer rates. In this paper, Al2O3 nanofluid heat transfer characteristics are investigated experimentally. Particle diameter of 31nm Al2O3 is taken into consideration in experiments. Impingement surface (surface area:780mm2) were made from oxygen-free copper to simulate high heat flux dissipating electronic component. The experimental results show that the suspended nanoparticles remarkably increase the convective heat transfer coefficient of the base fluid.. Nanofluids with particle volume fractions up to 4% can provide significant heat transfer enhancement, on the other hand, it has been found that high volume fractions (higher then 6%), is not appropriate for heat transfer enhancement under the free jet array configuration. Within the range of parameters considered in this study, experimental results indicated that maximum heat transfer coefficient can be obtained for the intermediate jet to heated target distance (around five times of jet diameter) and closely spaced jets (S/D = 3) for the particle volume fraction 2%. Closely spaced jets are particularly suitable for the electronics cooling applications with regards to provide temperature uniformity on the heated surface.

Heat transfer performance of steam/air flow in inverted V-shaped rib-roughened channels

2021 ◽  
pp. 095765092110161
Author(s):  
Chao Ma ◽  
Bing Ge
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Performance ◽  
Air Flow ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Ribbed Channel

The heat transfer performance of steam and air flow in a rough rectangular channel with different inverted V-shaped ribs was investigated by infrared thermal imaging technology. Under the conditions that the Reynolds number is in the range of 4000–15,000, the effects of the rib angle on the heat transfer enhancement of the two coolants were obtained. The rib pitch ratio of the flow channel is 10, the ratio of the rib height to the channel hydraulic diameter is 0.078, and the inverted V-shaped rib angle varies from 45° to 90°. The results show that in the inverted V-shaped ribbed channel, the Nu number on both sides of the channel is greatly increased, while the Nu number in the middle of the channel is lower. The local Nu distribution on the surface of the ribbed channel is highly related to the shape of the rib. For different medium cooling, the value and unevenness of the heat transfer coefficient are different, but the shape of the high and low heat transfer coefficient distribution is hardly affected. The heat transfer of both coolants increases as the rib angle decreases from 90° to 45°. Compared with air flow, steam flow cooling shows higher convective heat transfer enhancement. For rib angles of 45°, 60°, 75°, and 90°, under the operating condition of the Reynolds number = 12,000, the area-averaged Nusselt numbers of the steam flow is 23.6%, 27.4% and 13.9% higher than that of the air flow, respectively. Based on the experimental heat transfer data, the correlation in terms of the Reynolds number and the rib angle was developed, which is used to estimate the Nu number for steam and air cooling in the inverted V-shaped rib-roughness channels.

Experimental and Numerical Investigations on the Heat Transfer of Film Cooling With Cylindrical Holes Fed With Internal Coolant Cross Flows

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Lin Ye ◽  
Cun-Liang Liu ◽  
Dao-En Zhou ◽  
Hui-Ren Zhu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Cross Flow ◽  
Skewed Distribution ◽  
Transfer Enhancement ◽  
High Heat Transfer ◽  
Cylindrical Holes ◽  
The Heat Transfer Coefficient

Abstract The heat transfer coefficient of cylindrical holes fed by varying internal cross-flow channels with different cross-flow Reynolds numbers Rec is experimentally studied on a low-speed flat-plate facility. Three coolant cross flow cases, including a smooth case and two ribbed cases with 45/135-deg ribs, are studied at Rec = 50,000, and 100,000 with varying blowing ratios M of 0.5, 1.0, and 2.0. A transient liquid-crystal (LC) measurement technique is used to determine the heat transfer coefficient. At lower M, the heat transfer enhancement regions are asymmetrical for the smooth and 45-deg cases. The asymmetrical vortex is more pronounced with increasing cross-flow direction velocity, resulting in a more skewed distribution at Rec = 100,000. Conversely, the contours are laterally symmetric in the 135-deg case at varying Rec. A fork-shaped trend with a relatively high heat transfer coefficient appears upstream, and the increases in the heat transfer in the 135-deg cases are lower than those in the 45-deg cases. As M increases to 2.0, the vortex intensity increases, resulting in a stronger scouring effect upstream, especially at large Rec. The range and degree are affected by Rec at M = 2.0. The core of the heat transfer enhancement is skewed to the −Y side for both cases.

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