Heat transfer improvement in a tube by inserting perforated conical ring and wire coil as turbulators

Abbaspour, Mohammadreza; Ajarostaghi, Seyed Soheil Mousavi; Rad, Seyyed A. H. Hejazi; Nimafar, M.

doi:10.1002/htj.22167

Cited by 21 publications

(8 citation statements)

References 60 publications

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“…The continuous phase 3-D incompressible, steady, and pressure based equations with gravity source term is considered as general specifications of model. Turbulence Reynolds Averaged Navier-Stokes equations with the k-ε model [33][34][35][36][37][38][39][40] is supposed to solve the conversation of mass, momentum, and energy equations of the model. The SIMPLE algorithm is used to solve pressure and velocity coupling equations.…”

Section: Geometry Physical Specification and Grid Generationmentioning

confidence: 99%

Thermal analysis on the impact of spray charactristics on evaporative cooling process

Amoli

Ajarostaghi

SEDIGHI

et al. 2022

Journal of Thermal Engineering

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In hot and dry climates, evaporative cooling of the air by water spray can be applied in several requirements, such as evaporative condensers which the airflow is precooled by the water spray before it reaches the condenser. The interaction between water droplets and the air is a complicated two-phase flow that is affected by the several parameters. Here, an Eulerian-Lagrangian 3D model was developed to investigate the influence of important parameters on spray cooling performance in a rectangular duct. The evaluated parameters include the number of nozzles, inlet air flow rate, and spray water flow rate. The results represented that growth in the number of nozzles causes a reduction in the spray cooling efficiency. Thi s is due to decrease of droplets retention time within the duct by increasing the number of nozzles at a constant total spray flow rate in the cases. The maximum and minimum spray cooling efficiency belong to the cases with one nozzle at water flow rate of 20 l/h and four nozzle at water flow rate of 5 l/h, respectively. The difference between spray cooling efficiency at 3 and 4 number of nozzles is less than 1.8%. Moreover, increasing the air flow rate from 0.5 l/h to 2 l/h (by 300%) makes a decrease in the spray cooling efficiency up to 58.6%.

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Section: Geometry Physical Specification and Grid Generationmentioning

confidence: 99%

Thermal analysis on the impact of spray charactristics on evaporative cooling process

Amoli

Ajarostaghi

SEDIGHI

et al. 2022

Journal of Thermal Engineering

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“…The works of Garcia et al [12], Hong et al [14], and Gholamalizadeh et al [15] review experimental and numerical research work by other authors and present modifications in the design of wire coils over time. These works and design changes can be divided into: research with traditional geometry that tries to find empirical equations for Nusselt number and optimal geometry for given working conditions [11,12,16,17], modifications in wire geometry [18,19] that includes the usage of serrated wire coils [19], combined implementation with other turbulators [4,21], with modified inlet section [9], and with varying pitch and width [14,22].…”

Section: Introductionmentioning

confidence: 99%

Experimental and CFD analysis of wire coil turbulators in biomass boilers

et al. 2023

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To achieve as complete fuel burnout with as little excess air as possible, small wood log boilers (< 50 kW) use stage combustion. The first stage is often a process similar to downdraft gasification that consequently produces a flue gas laden with particulates. To prevent the build-up of solids and promote heat transfer in pipes of the convective part of these boilers, wire coils are used. The paper presents their in-situ examination together with CFD analysis. The analysis is carried out in a 460 mm long pipe, with a diameter of 82.5 mm, equipped with different wire coils for flue gas temperatures in the range between 300?C and 150?C. The analyzed coils are with and without a conical spring at their free end. The addition of this conical top is economical and should influence the rotation of the core flow. Proper pipe surface cleaning limited the analyzed wire coil designs to the dimensionless pitch, p/d, in the range between 0.36-0.61, dimensionless wire diameter e/d = 0.04-0.1, and pitch to wire diameter ratios p/e = 3.75-14.3, and three different angles (60?, 90?, and 120?) of the conical top. The goals are to find the optimal flue gas velocity for the given operating conditions, pipe, and wire coil dimensions, and to investigate the addition of the conical top on heat transfer enhancement. Several evaluation criteria are used to achieve the goals.

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“…The thermo-hydraulic behaviour in laminar, transition, and turbulent flows was investigated experimentally by putting a helical wire coil inside a plain tube [11]. It was discovered that the combined helical wire coil and the plain tube yielded an acceleration of transition flow at a Reynolds number of 700.…”

Section: Introductionmentioning

confidence: 99%

CFD Study of Behavior of Transition Flow in Distinct Tubes of Miscellaneous Tape Insertions

Oni

2022

HighTech. Innov. J.

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Application of transition flow can be found in several processes and systems. It has been revealed through findings from various researchers that the values of Reynolds numbers at which transition flow occurs vary. In the current work, investigations were numerically conducted by Fluent on transition of water flow in three assorted plain tubes fitted with miscellaneous tape insertions. They are plain tube with crossed-axes-circle-cut tape insert (C-C tube), plain tube with crossed-axes-triangle-cut tape insert (C-T tube), and plain tube with crossed-axes-ellipse-cut tape insert (C-E tube). The focus of the work is to explore the influence of the tape insertion on commencement and finish of transition flow in the tubes with respect to the Reynolds number of the flow. The Reynolds number (Re) taken into account for the transition flow is 2,150≤Re≤4,650, and the variation of Shear-Stress Transport κ-ω model that deals with transition flow was utilized. The results showed that transition flow starts at Re=2,300 and finishes at Re=4,400 in C-T tube, starts at Re=2,780 and finishes at Re=4,610 in C-C tube, but starts at Re=2,550 and finishes at Re=4,500 in C-E tube. The Nusselt number in C-T tube is 19.3% to 45.6% higher than that in C-C tube, but the Nusselt number in C-T tube is 3.6% to 28.3% more than that in C-E tube. The friction factor in C-T tube is 2.15% to 4.56% higher than that in C-C tube; the friction factor in C-T tube is 0.83% to 3.33% more than that in C-E tube. These results indicate that for the case of the tubes considered in this work, the C-T tube, which is the first one in which transition flow commences and ends, has the highest Nusselt number, but C-C tube, in which transition flow commences and finishes last, has the least Nusselt number. Interestingly, the same phenomenon applies to the friction factor. Doi: 10.28991/HIJ-2022-03-02-02 Full Text: PDF

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Heat transfer improvement in a tube by inserting perforated conical ring and wire coil as turbulators

Cited by 21 publications

References 60 publications

Thermal analysis on the impact of spray charactristics on evaporative cooling process

Thermal analysis on the impact of spray charactristics on evaporative cooling process

Experimental and CFD analysis of wire coil turbulators in biomass boilers

CFD Study of Behavior of Transition Flow in Distinct Tubes of Miscellaneous Tape Insertions

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