Spatially-resolved heat transfer and flow structure in a rectangular channel with pin fins

Won, Se Youl; Mahmood, Gazi I.; Ligrani, Phillip M.

doi:10.1016/j.ijheatmasstransfer.2003.10.007

Cited by 73 publications

(31 citation statements)

References 24 publications

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“…The thermal analysis is related to ink flow visualizations in order to better understand the effects of the main flow field on the thermal exchange capacities of every pin-fin inside the line. Nusselt numbers and flow structural characteristics are presented by Won et al [9] for a stationary channel with an aspect ratio of 8 and a staggered array of pin-fins between two of the surfaces. Local Nusselt numbers, measured on one end wall, are highest beneath primary and secondary horseshoe vortices located just upstream of individual pin-fins.…”

Section: Introductionmentioning

confidence: 99%

Thermal performance and pressure drop of different pin-fin geometries

Kotcioğlu¹,

Ömeroğlu²,

Çalışkan³

2014

Hittite J Sci Eng

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A B S T R A C TT he purpose of this study is to show the performance of hexagonal, square and cylindrical pin-fin arrays in improving heat transfer. In the present study, the thermal performance and pressure drop of the pin-fin heat exchanger are studied. The heat exchanger consists of cylindrical, hexagonal and square pin-fins. These types of pin-fins are capable of producing beneficial effects in transport enhancement and flow control. The pin-fins were arranged in an in-line manner. The relative longitudinal pitch (S L /D=2), and the relative transverse pitch were kept constant (S T /D=2). Air and water are used as working fluids in shell side and tube side, respectively. The inlet temperatures of air are between 50 and 90° C. The cold water entering the heat exchanger at the inner channel flows across the fin and flows out at the inner channel. Such pin-fins show potential for enhancing the heat transfer rate in pin-fin cross flow heat exchangers. Key Words:Thermal performance; Pressure drop; Cylindrical, Hexagonal and square ins I. Kotcioglu et. al./ Hittite J Sci Eng, 2014, 1 (1), [13][14][15][16][17][18][19][20] 14 N eeds for small-size and light-weight heat exchanger devices in power, process, computer and aerospace industries have resulted heat transfer surfaces. In order to enhance heat transfer between the flowing fluid and closely-spaced pin fins, in the case of pin-fin heat exchangers, pin-fins can be mounted on the channel surfaces.Jeng et al. [1] experimentally studied the pressure drop and heat transfer of a square pin-fin array in a rectangular channel by using the transient single-blow technique. The in-line square pin-fin array has smaller pressure drop than the in-line circular pin-fin array. The optimal inter-fin pitches of in-line square pin fin arrays are Xt = 2 and X L = 1.5, its Nu D * is around 20% higher than that of the in-line circular pin-fin array. Vanfossen [2] studied heat transfer by short pin-fins in staggered arrangements. According to their results, longer pin-fins transfer more heat than shorter pin-fins and the array-averaged heat transfer with eight rows of pin-fins slightly exceeds that with only four rows. Their results also established that the average heat transfer coefficient on the pin surface is around 35% larger than that on the end walls.Grannis and Sparrow [3] used the experiments to verify the accuracy of a numerical simulation of fluid flow through a diamond-shaped pin-fin array. They provided a correlation between the friction factor and the Reynolds number based on the results of numerical calculations.

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Section: Introductionmentioning

confidence: 99%

Thermal performance and pressure drop of different pin-fin geometries

Kotcioğlu¹,

Ömeroğlu²,

Çalışkan³

2014

Hittite J Sci Eng

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“…In order to protect these equipments and machines from being operated at the over high-temperature condition, the effective cooling system is necessary. Combining the finned heat sink with the steady flow of fixed flow rate is one of the simple and effective cooling technologies [1][2][3][4][5][6]. Besides, heat transfer in the oscillating flow has been a principal investigation area for past several decades.…”

Section: Introductionmentioning

confidence: 99%

Flow Visualization and Heat Transfer Characteristics of Oscillating Fluid through Pin-Fin Array in a Rectangular Channel

Jeng

Tzeng

Hsu

et al. 2013

Advances in Mechanical Engineering

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This work experimentally investigated the fluid flow and heat transfer characteristics of the pin-fin heat sink with the oscillating air flow. The oscillating air flow would be unstable in the passages among the fins due to the periodical change of flow rate. It might enhance the overall heat-transfer performance. At the present study, the pin-fin heat sinks with various fin heights were installed in the rectangular channel, resulting in different bypass clearances between the pin fins and the shroud of the test channel. The smoke flow visualizations for the oscillating-flow system were completed. The heat-transfer tests under the asymmetrically heated condition were performed to obtain the average Nusselt numbers. The smoke lines with obvious waves in the transverse direction were found in the results of the flow visualizations. By comparing to the steady flow system, there was about 20∼34% increment in the overall heat-transfer performance at the operating state without bypass clearance. However, if the bypass clearance was too big, the heat-exchange capacity of the oscillating flow was less than that of the steady flow. It demonstrates that the oscillating flow promotes the cooling performance of pin-fin heat sink at the non-bypass and specified bypass conditions.

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“…Zdravkovich [137] indicated the role of the fins as vortex-spoilers as they disturb the shed vortices, making them less coherent and threedimensional. Moreover, other studies on vortex shedding of finned tubes show that the vortex shedding frequency is well correlated with the tube effective diameter, which is based on the projected frontal area of the tube (Mair et al [142], Hamakawa et al [143] and Ligrani et al [139]). Unlike the mentioned studies on the detached structures from the wake of finned and bare tubes, no specific investigation has been conducted in the literature regarding the foam-wrapped tube type.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of detached structures from the wake, studies show that attaching extra surfaces to a tube affects the shedding process [137,[139][140][141][142][143]. Won et al [140] reported that adding fin causes intense, highly unsteady secondary flows and vortex pairs which increase secondary advection and turbulent transport.…”

Section: Introductionmentioning

confidence: 99%

“…Extensive reviews about the effects of Reynolds number on the characteristics of the wake of a cylinder are presented by Roshko [135], Berger & Wille [136] and Zdravkovich [137]. Furthermore, it is thought that the attached fin or foam (to the cylinder) affects the flow structures [139][140][141]. However, very limited experimental researches have been conducted in this area.…”

Section: Introductionmentioning

confidence: 99%

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Wake behind a rough (metal foam-covered) cylinder in cross-flow

Abdi¹

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The flow structures behind a circular cylinder are associated with various instabilities. These instabilities are characterized by the Reynolds number and they include the wake, separated shear layer and boundary layer. Depending on the physical application of the cylinder, increasing the level of turbulence by wrapping the cylinder with metal foam would be a target for drag reduction or heat transfer enhancement.In contrast to the extensive consideration that has been devoted to the flow around bare cylinders, the flow structures around the foam-covered cylinders and the characteristics of the wake behind such surfaces has received relatively little attention. Since the present study explores the possibility of using metal foams as replacements for fins on heat exchanger tubes, investigation on the flow-field structures downstream of a foam-covered cylinder and compare it to the bare cylinder specifies the feasibility of using the foamcovered cylinders in heat exchangers. Moreover, the outcome of this study can be used to develop an appropriate boundary condition for the porous-air interface modelling also increases the knowledge of turbulence in porous media.As it will be discussed more in detail in the following chapters, pressure drop and drag coefficient are directly linked to the wake and recirculation region, and to study these two phenomena, it is necessary to have in depth study on the flow-field down-stream of the cylinder. Hence, the purpose of this study is to investigate the wake region behind a foam- Moreover, using hot-wire anemometry, to investigate the energy of the flow inside and outside of the foam-covered cylinder's wake, let us know if a foam-covered cylinder can be treated as an obstacle to the incident flow with a rough surface or the whole foam can be considered as the combination of local jets that are coming out of the pores and disperse in random directions.III

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Spatially-resolved heat transfer and flow structure in a rectangular channel with pin fins

Cited by 73 publications

References 24 publications

Thermal performance and pressure drop of different pin-fin geometries

Thermal performance and pressure drop of different pin-fin geometries

Flow Visualization and Heat Transfer Characteristics of Oscillating Fluid through Pin-Fin Array in a Rectangular Channel

Wake behind a rough (metal foam-covered) cylinder in cross-flow

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