Thermal characteristics of fin-and-tube heat exchanger cooled by natural convection

Kayansayan, N.

doi:10.1016/0894-1777(93)90001-y

Cited by 22 publications

(7 citation statements)

References 8 publications

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“…Additionally, the natural convection of inclined plain tubes at angles between 0°a nd 90°was studied and it was found that the heat transfer reduces with inclination angle. Geometrical parameters such as fin diameter, fin spacing and temperature difference, were varied in the study of Kayansayan to understand their impact on the heat transfer [5]. It was found, that the beneficial ratio between fin spacing and fin diameter is between 0.25 and 0.5.…”

Section: Introductionmentioning

confidence: 99%

Natural convection heat transfer performance of additively manufactured tube bundle heat exchangers with novel fin design

et al. 2021

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We studied the heat transfer of finned heat exchanger configurations with a novel design. These novel fin designs use integrated pins to enhance the heat conduction from the fin base to the fin tip as well as the air-side heat transfer on the fin surface. Oval tubes with conventional circular plain fins (CPF) as well as novel circular integrated pin fins (CIPF) and serrated integrated pin fins (SIPF) were additively generated by a Selective Laser Melting (SLM) process and installed at the bottom of a 6.5 m long chimney. All heat exchanger designs were tested in a 2-row and 3-row configuration with Rayleigh numbers between 25,000 and 120,000. We found the average Nusselt number of SIPF to be higher and the Nusselt number of the CIPF to be lower than for the CPF. Moreover, the 2-row configuration achieved a higher Nusselt number compared to the 3-row configuration for all heat exchanger designs. The analysis of the individual tube rows showed the highest Nusselt numbers at the first tube row and the lowest one at the last tube row for both configurations. However, for the SIPF the difference between the first and second tube row is smaller compared to the CPF and CIPF. In order to evaluate the compactness of the heat exchanger, the volumetric heat flux density was considered. Similar to Nusselt number the volumetric heat flux density enhanced for the SIPF and reduced for the CIPF compared to the conventional design. Also the 2-row configuration reached greater thermal performance compared to the 3-row configuration. Additionally, the volume and the surface area of the heat exchanger are 6.9% and 30.7% lower for the SIPF compared to the CPF. The experimental data were used to develop an empirical heat transfer correlation between Nusselt number, Rayleigh number, fin design and tube row number.

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Section: Introductionmentioning

confidence: 99%

Natural convection heat transfer performance of additively manufactured tube bundle heat exchangers with novel fin design

et al. 2021

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“…Covering the tubes with conventional fins is one way to increase the contact area so that it can improve the thermal performance of a bare tube bundle, however because of the blockage and the tubes' wake, it raises the pressure drop. Therefore, designing and optimizing finned tube heat exchangers have been widely studied to increase the heat transfer and, at the same time, reduce the air side pressure drop [1][2][3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Coherence behind a Single Foamed Tube

Abdi¹,

Khashehchi²,

Hooman³

2017

FMRIJ

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In this paper the flow structures downstream of a foamed tube are compared to those of a bare tube with the same frontal areaand length. Experiments were conducted in a wind tunnel at Reynolds numbers 4000 and 16000. Particle image velocimetry (PIV) was used to obtain velocity vector field in two different perpendicular planes. To measure the effect of flow three-dimensionality, field of divergence on both planes was obtained and compared with each other. Moreover, to characterize the size of the flow structures downstream of the tube, for each of the aforementioned cases, two-point correlation functions were used as the statistical analysis tool. Analysis showed that, compared to the bare tube, the foamed one, in the X-Z plane (stream-wise, span-wise) increases the threedimensionality of the flow which is set forward in the perpendicular plane despite being less pronounced. Moreover, the structures downstream of a foamed tube are elongated in the stream-wise direction and are linearly independent of the inlet velocity, however, in span-wise and normal direction no significant change in the size of the structures between bare and foamed tube has been observed.

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“…This fact has been well aware and can be traced back in time to the early day of thermal engineering discipline. Kays and London (1955) [11] wrote in a very beginning paragraph of page (1) Following the pioneers of the field in the 60's such as Kays and London (1955) [11], Briggs and Young (1963) [12], Robinson and Briggs (1966) [13], are publications from newer generation researchers -the like of Rabas, et al (1981) [14], Kayansayan (1993) [15], and Jang, et al (1998) [16]. At the turn of the century, the next wave of names emerged.…”

Section: Performance Enhancement Of Conventional Heat Exchangersmentioning

confidence: 99%

Improving the performance of air-cooled condensers by using metal foams

Chumpia¹

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This research investigates the implementation of porous metals particularly aluminum foam as an enhanced surface to improve heat transfer on the air side of air-cooled, tubular heat exchangers. The target application for these heat exchangers is the condensers for geothermal power plants in remote locations of Australia where water for wet cooling is scarce. Traditional practices for liquid-to-air or vapor-to-air heat exchangers rely predominantly on finned surfaces to enhance heat transfer rate. Heat transfer enhancement in these designs is achieved via an increased surface area of simple geometries. Recent advancement in manufacturing and availability of porous materials make them possible to be utilized in thermal exchange equipment to improve efficiency and compactness.This work describes heat exchanger tubes based on circular cylinders with aluminum foam covering on the outer surface. Thermo-hydraulic performances are evaluated experimentally in a cross-flow using low-speed wind tunnel. The tests are performed on single cylinders, single row arrays, and multi-row tube bundles in both aligned and staggered configurations subjected to airflow of 0.5 to 5.0 m/s. This range of air velocities is chosen as it encompasses vertical flow regimes occur inside typical cooling towers. The effects of foam layer thickness, transversal and longitudinal tube pitches, foam-to-tube bonding methods, and tube bank patterns, are collectively investigated. The results are compared to baseline data obtained from conventional, annular finned tubes and tube bundles tested under the same conditions.The overall conclusions are drawn on heat transfer and pressure drop as two main comparison parameters. Experimental results on these parameters confirm the trend of numerical findings of a previous in-house study, although with varying degrees of differences on their magnitude. In all finned-versus foam-surface comparisons, under the same testing conditions and using specimens of similar dimensions, the latter shows convincing benefits on heat transfer/pressure drop ratios over the full range of chosen airflows. Within this range, the maximum relative advantage of the foam-covered heat exchangers over the finned type is observed at the midrange of airflow between 2.0 and 2.5 m/s. This result is both desirable and opportune because these designated airflows coincide with the top end velocity found inside most natural-draft cooling towers. Beyond this range of airflow up to 5.0 m/s, a typical range at the lower end of induced-or forced-draft cooling towers, the relative merit of heat transfer/pressure drop is rapidly degraded. However, in a situation where the increased heat transfer is under demand and compactness is not a critical factor, the pressure drop can be reduced satisfactorily by choosing a suitable transversal pitch within the tube bundle. Under this reduced blockage condition, metal foam heat exchanger bundles tend to behave as a group of an individual tube; therefore, retain higher relative benefit in terms of the sum...

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Thermal characteristics of fin-and-tube heat exchanger cooled by natural convection

Cited by 22 publications

References 8 publications

Natural convection heat transfer performance of additively manufactured tube bundle heat exchangers with novel fin design

Natural convection heat transfer performance of additively manufactured tube bundle heat exchangers with novel fin design

Investigation of Coherence behind a Single Foamed Tube

Improving the performance of air-cooled condensers by using metal foams

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