Design Optimisation of Finned Channel

2009 ◽  
Author(s):  
K. M. C. Seakher ◽  
L. S. S. Prakash Kumar ◽  
K. S. R. Kali Prasad ◽  
K. H. Manasa ◽  
A. Siva Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Pumping Power ◽  
Transfer Enhancement ◽  
Power Requirement ◽  
Smooth Channel ◽  
Fin Length

A finned channel has a higher heat transfer coefficient compared to a smooth channel and the increase in this fin height enhances the heat transfer. But this heat transfer enhancement is accompanied by an increase in pressure drop for a series of fins. This requires an increase in pumping power requirement, indicating that there exists an optimum design or length of the fin at which the heat dissipation is maximum. The objective of this paper is to observe the variation of heat transfer with varying sizes of fins. The effect of fin dimensions on heat transfer can be clearly seen in its performance, which is discussed in the paper. The results are obtained by analytical analysis, and some illustrations are dealt with in the paper, which clearly determine the importance of this factor of optimal fin length.

Experimental Investigation of Crossflow Diverters in Jet Impingement Cooling

2019 ◽  
Author(s):  
Srivatsan Madhavan ◽  
Kishore Ranganath Ramakrishnan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Target Surface ◽  
Pumping Power ◽  
Detailed Measurement ◽  
To Come

Abstract Jet impingement is a cooling technique commonly employed in combustor liner cooling and high-pressure gas turbine blades. However, jets from upstream impingement holes reduce the effectiveness of downstream jets due to jet deflection in the direction of crossflow. In order to avoid this phenomenon and provide an enhanced cooling on the target surface, we have attempted to come up with a novel design called “crossflow diverters”. Crossflow diverters are U-shaped ribs that are placed between jets in the crossflow direction (under maximum crossflow condition). In this study, the baseline case is jet impingement onto a smooth surface with 10 rows of jet impingement holes, jet-to-jet spacing of X/D = Y/D = 6 and jet-to-target spacing of Z/D = 2. Crossflow diverters with thickness ‘t’ of 1.5875 mm, height ‘h’ of 2D placed in the streamwise direction at a distance of X = 2D from center of the jet have been investigated experimentally. Transient liquid crystal thermography technique has been used to obtain detailed measurement of heat transfer coefficient for four jet diameter based Reynolds numbers of 3500, 5000, 7500, 12000. It has been observed that crossflow diverters protect the downstream jets from upstream jet deflection thereby maximizing their stagnation cooling potential. An average of 15–30% enhancement in Nusselt number is obtained over the flow range tested. However, this comes at the expense of increase in pumping power. Pressure drop for the enhanced geometry is 1–1.5 times the pressure drop for baseline impingement case. At a constant pumping power, crossflow diverters produce 9–15% enhancement in heat transfer coefficient as compared to baseline smooth case.

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.

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 Dissipation Beyond 1 kW/cm2 With Low Pressure Drop and High Heat Transfer Coefficient for Flow Boiling Using Open Microchannels With Tapered Manifold

2016 ◽  
Author(s):  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Low Pressure ◽  
High Heat ◽  
High Heat Transfer ◽  
High Heat Transfer Coefficient

Heat dissipation beyond 1 kW/cm2 accompanied with high heat transfer coefficient and low pressure drop using water has been a long-standing goal in the flow boiling research directed toward electronic cooling application. In the present work, three approaches are combined to reach this goal: (a) a microchannel with a manifold to increase critical heat flux (CHF) and heat transfer coefficient (HTC), (b) a tapered manifold to reduce the pressure drop, and (c) high flow rates for further enhancing CHF from liquid inertia forces. A CHF of 1.07 kW/cm2 was achieved with a heat transfer coefficient of 295 kW/m2°C with a pressure drop of 30 kPa. Effect of flow rate on CHF and HTC is investigated. High speed visualization to understand the underlying bubble dynamics responsible for low pressure drop and high CHF is also presented.

Analysis of a Screen Heat Exchanger

1992 ◽  
Vol 114 (4) ◽  
pp. 887-892 ◽  
Author(s):  
G. F. Jones ◽  
F. C. Prenger
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Convection Heat Transfer ◽  
Axial Conduction ◽  
Pin Fins ◽  
Fin Length

Heat transfer in a fluid-to-fluid screen heat exchanger is analyzed from first principles. The screens are treated as an ensemble of pin fins and an empirical heat transfer coefficient accounts for convection heat transfer at the fin surface. Pressure drop and simultaneous axial conduction in the screen matrix and the wall separating the fluid streams are modeled. Expressions are obtained that relate dimensionless length ratios to exchanger effectiveness and pressure drop. The “mesh ratio,” defined as the ratio of fin diameter (d) to spacing (s), prevails throughout the results. The key findings are: (1) the existence of an optimal ratio of fin length (a) to fin diameter that maximizes thermal performance (arising from the competition between the fin-length dependent heat transfer coefficient and fin surface area), (2) increasing a/d greater than optimal increases exchanger length and reduces pressure drop; for a/d less than optimal heat transfer is depressed and pressure drop increased, and (3) the pressure drop is linear with overall Ntu and varies as d−2, (1 + d/s)6, and approximately the square of the mass flow rate per width of exchanger. An exact solution for axial conduction is presented that is valid in the limit of large Ntu and equal fluid capacity rates. Axial conduction is seen to decrease with increasing Ntu and mass flow rates and reduced fin a/d ratio. Predictions from the model are validated by comparing with published effectiveness and pressure-drop data.

Heat Transfer Enhancement in Narrow Diverging Channels

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Justin Lamont ◽  
Sridharan Ramesh ◽  
Srinath V. Ekkad ◽  
Anil Tolpadi ◽  
Christopher Kaminski ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Color Change ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer

Detailed heat transfer coefficient distributions have been obtained for narrow diverging channels with and without enhancement features. The cooling configurations considered include rib turbulators and concavities (or dimples) on the main heat transfer surfaces. All of the measurements are presented at a representative Reynolds number of 28,000. Pressure drop measurements for the overall channel are also presented to evaluate the heat transfer enhancement geometry with respect to the pumping power requirements. The test models were studied for wall heat transfer coefficient measurements using the transient liquid crystal technique. The model wall inner surfaces were sprayed with thermochromic liquid crystals and a transient test was used to obtain the local heat transfer coefficients from the measured color change. An analysis of the results shows that the choice of designs is limited by the available pressure drop, even if the design provides significantly higher heat transfer coefficients. Dimpled surfaces provide appreciably high heat transfer coefficients and a reasonable pressure drop, whereas ribbed ducts provide significantly higher heat transfer coefficients and a higher overall pressure drop.

Performance Investigation of a Plate Heat Exchanger Using Nanofluid with Different Chevron Angle

2013 ◽  
Vol 832 ◽  
pp. 254-259 ◽  
Author(s):  
M.M. Elias ◽  
Saidur Rahman ◽  
N.A. Rahim ◽  
M.R. Sohel ◽  
I.M. Mahbubul
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer Coefficient ◽  
Plate Heat Exchanger ◽  
Pumping Power ◽  
Plate Heat ◽  
Analytical Work

Plate heat exchanger with chevron angle has higher heat transfer area than flat type and increases the level of turbulent due to its corrugated channel. In this study, both water and nanofluid were used to determine the heat transfer coefficient and rate, pumping power, and pressure drop. A commercial plate heat exchanger with two different symmetric (300/300,600/600) and one mixed (300/600) chevron angle plates were considered for analysis. Al2O3and SiO2nanoparticles with 0-1 vol. % concentration were used with water. From the analysis it was found that, convective heat transfer coefficient, heat transfer rate, pressure drop and pumping power increases with the increase of volume concentration. Moreover, the above parameters were found to be higher for 600/600chevron angle plates. A correlation of Nusselt number as a function of Reynolds number and Prandtl number for different chevron angles needs to be obtained based on experimental and analytical work. Nomenclature

scholarly journals Experimental Investigation of Thermal and Pressure Performance in Computer Cooling Systems Using Different Types of Nanofluids

Nanomaterials ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1231 ◽  
Author(s):  
Alfaryjat ◽  
Miron ◽  
Pop ◽  
Apostol ◽  
Stefanescu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Base Fluid ◽  
Pumping Power ◽  
Cooling Systems

A modern computer generates a great amount of heat while working. In order to secure appropriate working conditions by extracting the heat, a specific mechanism should be used. This research paper presents the effect of nanofluids on the microchannel heat sink performance of computer cooling systems experimentally. CeO2, Al2O3 and ZrO2 nanoparticles suspended in 20% ethylene glycol and 80% distilled water are used as working fluids in the experiment. The concentration of the nanoparticles ranges from 0.5% to 2%, mass flow rate ranges from 0.028 kg/s to 0.084 kg/s, and the ambient temperature ranges from 25 °C to 40 °C. Regarding the thermal component, parameters such as thermophysical properties of the nanofluids and base fluids, central processing unit (CPU) temperature, heat transfer coefficient, pressure drop, and pumping power have been experimentally investigated. The results show that CeO2-EG/DW, at a concentration of 2% and a mass flow rate of 0.084 kg/s, has with 8% a lower temperature than the other nanofluids and with 29% a higher heat transfer coefficient compared with the base fluid. The Al2O3-EG/DW shows the lowest pressure drop and pumping power, while the CeO2-EG/DW and ZrO2-EG/DW show the highest. However, a slight increase of pumping power and pressure drop can be accepted, considering the high improvement that the nanofluid brings in computer cooling performance compared to the base fluid.

Heat Transfer and Pressure Drop Characteristics of a Liquid Cooled Manifold-Microgroove Condenser

2013 ◽  
Author(s):  
David Boyea ◽  
Amir Shooshtari ◽  
Serguei V. Dessiatoun ◽  
Michael M. Ohadi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Electronics Cooling ◽  
Pumping Power ◽  
Two Phase ◽  
Water Side ◽  
Essential Components

High performance condensers are essential components in energy conversion, electronics cooling and process systems. Increased capacity and functionality with less and less available space has been a main driving force for development of next generation of condensers in energy systems. Our previous work in this area has demonstrated that manifold-microgroove heat exchangers operating in single-phase or two-phase modes offer substantially higher heat transfer performance with a greatly reduced pumping power when compared to state-of-art microchannel heat exchangers. The goal is to enhance heat transfer while minimizing the pumping power, volume and weight. A compact lightweight manifold microgroove condenser, with 60 × 600 micron microgrooves and cooling capacity of 4kW, was fabricated, assembled and tested using different manifolds. Experiments using R236fa and R134a as a working fluids were performed measuring inlet and outlet temperatures, flow rates and pressure drops for the refrigerant and water side. Overall heat transfer coefficient and pressure drop across condenser were determined and refrigerant side heat transfer coefficient were calculated based on water side heat transfer coefficient. Experimental results indicate significant effect of manifold geometry on condenser performances. Refrigerant side heat transfer coefficient of 60 kW/m2K with pressure drop of just 7 kPa has been demonstrated using R-134-a.

Measurement of Heat Transfer Enhancement and Pressure Drop Across Eddy Promoter Air Screens in a Liquid-to-Air-Membrane Energy Exchanger (LAMEE)

2013 ◽  
Author(s):  
Ashkan Oghabi ◽  
Davood Ghadiri Moghaddam ◽  
Carey Simonson ◽  
Robert W. Besant
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Convective Heat Transfer Coefficient ◽  
Transfer Enhancement ◽  
Membrane Energy ◽  
Air Channel

In liquid-to-air membrane energy exchangers (LAMEEs), the heat and mass transfer resistances in the air channel are dominant. An eddy promoter air screen can effectively enhance the heat and mass transfers in the air channel. In this study, the heat transfer enhancement and pressure drop across three different eddy promoter air screens in an air channel are experimentally investigated. Eddy promoter air screens are comprised of plastic ribs in the stream-wise direction and aluminum cross-bars normal to the air flow direction. A low speed wind tunnel test facility, which simulates the air channel of a LAMEE is designed to measure the friction factor and enhanced convective heat transfer coefficient in the air channel with an eddy promoter air screen. Tests were conducted at Reynolds numbers of 920, 1550, and 2160. In this paper, the effects of the spacing of the cylindrical bars and plastic ribs on the heat transfer performance are studied experimentally. Also, the performance of eddy promoter air screens as a function of enhanced heat transfer coefficient and increased pressure drop is investigated. Results show that the eddy promoter air screens have the highest efficiencies at Reynolds of 1550 and double the convective heat transfer coefficient of the air with respect to a smooth channel.

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