Optimal Spacing Between Pin Fins With Impinging Flow

1996 ◽  
Vol 118 (3) ◽  
pp. 570-577 ◽  
Author(s):  
G. Ledezma ◽  
A. M. Morega ◽  
A. Bejan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductance ◽  
Base Plate ◽  
Maximum Heat ◽  
Air Stream ◽  
Maximum Heat Transfer ◽  
Pin Fins ◽  
Plate Size ◽  
Optimal Spacing ◽  
Fin Thickness

This is an experimental numerical and theoretical study of the heat transfer on a pin-finned plate exposed to an impinging air stream. The pin fins are aligned with the air approach velocity. The base plate and the fin cross section are square. It is demonstrated experimentally that the thermal conductance between the plate and the air stream can be maximized by selecting the fin-to-fin spacing S. Next, a simplified numerical model is used to generate a large number of optimal spacing and maximum heat transfer data for various configurations, which differ with respect to fin length (H), fin thickness (D), base plate size (L), fluid type (Pr), and air velocity (ReL). Finally, the behavior of the optimal spacing data is explained and correlated theoretically based on the intersection of asymptotes method. The recommended correlations for optimal spacing, Sopt/L ≅ 0.81 Pr−0.25 ReL−0.32, and maximum thermal conductance, (q/ΔT)max/kaH ≅ 1.57 Pr0.45 ReL0.69 (L/D)0.31, cover the range D/L = 0.06 − 0.14, H/L = 0.28−0.56, Pr = 0.72−7, ReD = 10−700, and ReL = 90−6000.

The Optimal Distribution of Chordwise Rib Fin Arrays for Blade Tip Cap Underside Cooling

2012 ◽  
Author(s):  
Gustavo A. Ledezma ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Thermal Conductance ◽  
Maximum Heat ◽  
Heat Transfer Augmentation ◽  
Maximum Heat Transfer ◽  
Optimal Spacing ◽  
Blade Tip ◽  
Fin Spacing ◽  
Surrounding Fluid ◽  
Small Spacing

A fundamental question in the design of fin-augmented heat transfer surfaces is how to determine the optimal spacing between the fins. It has already been demonstrated that considerable heat transfer augmentation in the underside of an HPT turbine blade tip cap can be achieved using arrays of discrete shaped pins [5]. However, it is desirable to predict the maximum heat transfer augmentation that can be achieved by installing the array of fins and the geometric arrangement (fin-to-fin spacing) that has to be used to achieve such augmentation. In this paper chordwise parallel ribs installed on the underside of a blade tip cap are studied. The objective is to maximize the overall thermal conductance between the fin array and the surrounding fluid. The optimization is performed numerically in the range 25,000<Re<100,000 and Pr = 0.72. The behavior of the optimal spacing data is explained and correlated analytically using the method of intersecting the two asymptotes: small spacing and large spacing heat transfer [7].

The Optimal Distribution of Chordwise Rib Fin Arrays for Blade Tip Cap Underside Cooling

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Gustavo A. Ledezma ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Thermal Conductance ◽  
Maximum Heat ◽  
Heat Transfer Augmentation ◽  
Maximum Heat Transfer ◽  
Optimal Spacing ◽  
Blade Tip ◽  
Fin Spacing ◽  
Surrounding Fluid ◽  
Small Spacing

A fundamental question in the design of fin-augmented heat transfer surfaces is how to determine the optimal spacing between the fins. It has already been demonstrated that considerable heat transfer augmentation in the underside of a high-pressure turbine (HPT) blade tip cap can be achieved using arrays of discrete shaped pins (Bunker, 2008, “The Augmentation of Internal Blade Tip-Cap Cooling by Arrays of Shaped Pins,” ASME J. Turbomach., 130(4), p. 041007). However, it is desirable to predict the maximum heat transfer augmentation that can be achieved by installing the array of fins and the geometric arrangement (fin-to-fin spacing) that has to be used to achieve such augmentation. In this paper chordwise parallel ribs installed on the underside of a blade tip cap are studied. The objective is to maximize the overall thermal conductance between the fin array and the surrounding fluid. The optimization is performed numerically in the range 25,000 < Re < 100,000 and Pr = 0.72. The behavior of the optimal spacing data is explained and correlated analytically using the method of intersecting the two asymptotes: small spacing and large spacing heat transfer (Bejan and Morega, 1994, “The Optimal Spacing of a Stack of Plates Cooled by Turbulent Forced Convection,” Int. J. Heat Mass Trans., 37, pp. 1045–1048).

Investigation of Maximum Heat Transfer from an Aluminum Alloy Extended Surfaces

2017 ◽  
Vol 1 (2) ◽  
Author(s):  
Raad Muzahem Fenjan
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Extended Surfaces ◽  
Steady State Heat ◽  
Steady State Heat Transfer ◽  
Vertical Base ◽  
Fin Thickness ◽  
Fin Length

The aim of this research is to obtain the maximum steady state heat transfer used aluminum alloy extended surfaces which obtain the optimal design for these fins. For three cases, (according to both dimension and direction of the extended surfaces): vertical fins extended from horizontal base, vertical fins extended from vertical base , and horizontal fins extended from vertical base, the natural convective, conductive and radiative heat transfer was studied experimentally and respectively the comparison between these cases were achieved.  The parameters studied were distance between fins, fin length fin thickness and fin protrusion.

scholarly journals Maximum Heat Transfer Rate Density in Two-Dimensional Minichannels and Microchannels

2003 ◽  
Author(s):  
M. Favre-Marinet ◽  
S. Le Person ◽  
A. Bejan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Transition To Turbulence ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Parallel Plates ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Optimal Spacing

Experimental investigations of the flow and the associated heat transfer were conducted in two-dimensional microchannels in order to test possible size effects on the laws of hydrodynamics and heat transfer and to infer optimal conditions of use from the measurements. The test section was designed to modify easily the channel height e between 1 mm and 0.1 mm. Measurements of the overall friction factor and local Nusselt numbers show that the classical laws of hydrodynamics and heat transfer are verified for e > 0.4 mm. For lower values of e, a significant decrease of the Nusselt number is observed, whereas the Poiseuille number continues to have the conventional value of laminar developed flow. The transition to turbulence is not affected by the channel size. For fixed pressure drop across the channel, a maximum of heat transfer rate density is found for a particular value of e. The corresponding dimensionless optimal spacing and heat transfer rate density are in very good agreement with the predictions of Bejan and Sciubba (1992). This paper is the first time that the optimal spacing between parallel plates is determined experimentally.

Maximum Heat Transfer From Multi-Scale Fins Arranged in a Row With Non-Uniform Geometry

2010 ◽  
Author(s):  
T. Bello-Ochende ◽  
J. P. Meyer ◽  
A. Bejan
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Thermal Conductivity Ratio ◽  
Total Heat Transfer ◽  
Maximum Heat ◽  
Optimum Configuration ◽  
Multi Scale ◽  
Maximum Heat Transfer ◽  
Pin Fins ◽  
Laminar Forced Convection

This paper described numerical the procedure used to determine the optimum configuration of two rows of pin fins so that the total heat transfer rate is maximized. The heat transfer across the fins is by laminar forced convection bathed by a free-stream that is uniform and isothermal. The optimization is subjected to fixed volume of fin materials. The dimensions of the optimized configuration are the result of balancing conduction along the fins with convection transversal to the fins. Numerical results on the effect of dimensionless pressure drop and the thermal conductivity ratio on the optimal configuration are reported. Results obtained from numerical analyses are comparable to those in the open literature. The results also show that the flow structure performs best when the fin diameters and heights are non-uniform.

scholarly journals Multi-scale pin fins: Scale analysis and mathematical optimization of micro-pin fins arranged in rows

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Tunde Bello-Ochende
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Mathematical Optimization ◽  
Thermal Conductivity Ratio ◽  
Maximum Heat ◽  
Pin Fin ◽  
Maximum Heat Transfer ◽  
Computational Fluid Dynamics Analysis ◽  
Pin Fins ◽  
Micro Pin Fins

AbstractThis paper shows the performance of a cylindrical micro-pin fins with multiples-arrays structures for maximum heat transfer. The structures has a varying geometric sizes (diameter, height and spacing). The effects of Reynolds number and thermal conductivity ratio on the optimized geometric configurations and the maximum heat transfer rate is documented. Two design configuration were considered. Scales and computational fluid dynamics analysis shows that the benefits of varying fin height is minimal. Results show that performace is increased when three rows of micro pin fin heat sinks with a reduced degree of freedom (fixed height) when compared to two rows of micro pin fins heat sink for the same amount of material. The optimized diameters of the fins seems to have greatest effect on perfomance of the heat sink.

scholarly journals A MCDM Methodology to Determine the Most Critical Variables in the Pressure Drop and Heat Transfer in Minichannels

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2069
Author(s):  
Eloy Hontoria ◽  
Alejandro López-Belchí ◽  
Nolberto Munier ◽  
Francisco Vera-García
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Saturation Pressure ◽  
Computational Cost ◽  
Urban Systems ◽  
Condensation Process ◽  
Geometrical Parameters ◽  
Maximum Heat ◽  
Maximum Heat Transfer

This paper proposes a methodology aiming at determining the most influent working variables and geometrical parameters over the pressure drop and heat transfer during the condensation process of several refrigerant gases using heat exchangers with pipes mini channels technology. A multi-criteria decision making (MCDM) methodology was used; this MCDM includes a mathematical method called SIMUS (Sequential Interactive Modelling for Urban Systems) that was applied to the results of 2543 tests obtained by using a designed refrigeration rig in which five different refrigerants (R32, R134a, R290, R410A and R1234yf) and two different tube geometries were tested. This methodology allows us to reduce the computational cost compared to the use of neural networks or other model development systems. This research shows six variables out of 39 that better define simultaneously the minimum pressure drop, as well as the maximum heat transfer, saturation pressure fluid entering the condenser being the most important one. Another aim of this research was to highlight a new methodology based on operation research for their application to improve the heat transfer energy efficiency and reduce the CO2 footprint derived of the use of heat exchangers with minichannels.

scholarly journals Significance of Shape Factor in Heat Transfer Performance of Molybdenum-Disulfide Nanofluid in Multiple Flow Situations; A Comparative Fractional Study

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3711
Author(s):  
Asifa ◽  
Talha Anwar ◽  
Poom Kumam ◽  
Zahir Shah ◽  
Kanokwan Sitthithakerngkiet
Keyword(s):  
Heat Transfer ◽  
Skin Friction ◽  
Molybdenum Disulfide ◽  
Heat Transfer Rate ◽  
Shape Factor ◽  
Transfer Rate ◽  
Maximum Heat ◽  
Left Wall ◽  
Maximum Heat Transfer ◽  
Mos2 Nanoparticles

In this modern era, nanofluids are considered one of the advanced kinds of heat transferring fluids due to their enhanced thermal features. The present study is conducted to investigate that how the suspension of molybdenum-disulfide (MoS2) nanoparticles boosts the thermal performance of a Casson-type fluid. Sodium alginate (NaAlg) based nanofluid is contained inside a vertical channel of width d and it exhibits a flow due to the movement of the left wall. The walls are nested in a permeable medium, and a uniform magnetic field and radiation flux are also involved in determining flow patterns and thermal behavior of the nanofluid. Depending on velocity boundary conditions, the flow phenomenon is examined for three different situations. To evaluate the influence of shape factor, MoS2 nanoparticles of blade, cylinder, platelet, and brick shapes are considered. The mathematical modeling is performed in the form of non-integer order operators, and a double fractional analysis is carried out by separately solving Caputo-Fabrizio and Atangana-Baleanu operators based fractional models. The system of coupled PDEs is converted to ODEs by operating the Laplace transformation, and Zakian’s algorithm is applied to approximate the Laplace inversion numerically. The solutions of flow and energy equations are presented in terms of graphical illustrations and tables to discuss important physical aspects of the observed problem. Moreover, a detailed inspection on shear stress and Nusselt number is carried out to get a deep insight into skin friction and heat transfer mechanisms. It is analyzed that the suspension of MoS2 nanoparticles leads to ameliorating the heat transfer rate up to 9.5%. To serve the purpose of achieving maximum heat transfer rate and reduced skin friction, the Atangana-Baleanu operator based fractional model is more effective. Furthermore, it is perceived that velocity and energy functions of the nanofluid exhibit significant variations because of the different shapes of nanoparticles.

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