Numerical study of the thermo-hydraulic characteristics in a circular tube with ball turbulators. Part 2: Heat transfer

Jasiński, Piotr Bogusław

doi:10.1016/j.ijheatmasstransfer.2014.02.073

Cited by 22 publications

(12 citation statements)

References 10 publications

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“…The k-ω SST was chosen as optimal and used for further validation against experimental data. It was utilized in many works where CFD analysis of the heat transfer for finned and enhanced surfaces was carried out [4,13,[19][20][21].…”

Section: Boundary Conditions and Governing Equationsmentioning

confidence: 99%

Study of the Influence of the Lack of Contact in Plate and Fin and Tube Heat Exchanger on Heat Transfer Efficiency under Periodic Flow Conditions

et al. 2021

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Plate fin-tube heat exchangers are widely used in air conditioning and refrigeration systems and other industry fields. Various errors made in the manufacturing process can result in the formation of an air gap between the tube and fin. Several numerical simulations were carried out for a symmetric section of plate fin-tube heat exchanger to study the influence of air gap on heat transfer under periodic flow conditions. Different locations and sizes of an air gap spanning 1/2 circumference of the tube were considered for the range of airflow velocities. Velocity and temperature fields for cases with air gap were compared with ideal thermal contact cases. Blocking of heat flow by the gap leads to the reduction of heat transfer rate. Fin discontinuity in the front of the tube causes the smallest reduction of the heat transfer rate in comparison to the ideal tube-fin contact, especially for thin slits. The rear gap position is the worst in the smallest gap range. Therefore, reversing the flow direction can lead to up to a 15% heat transfer increase, if mainly the rear gaps are present. The introduction of a thin slit in the front of the tube leads to convective heat transfer enhancement, which should be further investigated.

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Section: Boundary Conditions and Governing Equationsmentioning

confidence: 99%

Study of the Influence of the Lack of Contact in Plate and Fin and Tube Heat Exchanger on Heat Transfer Efficiency under Periodic Flow Conditions

et al. 2021

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“…By reducing the domain size and the number of computational mesh nodes (up to 2D), it was possible to significantly shorten the computation time while maintaining the high mesh quality. Such a research method has also been presented in [15][16][17], while other, less important details, generally related to such a method of numerical modelling, are presented in [18][19][20]. In order to ensure the same static pressure on both sides of the insert, small gaps in the continuity of the insert with a 2 mm length were made (Figure 2a), representing about 1.5% of the total length of the insert.…”

Section: Boundary Conditions Of Simulation and Numerical Modelmentioning

confidence: 99%

“…where the term ∇ • (Uτ w ) represents the work of viscous forces, S E is a term of an energy sources and the total enthalpy i tot is expressed as:i + 1 2 U 2 . For the turbulence model used, the governing equations are presented in detail in [17].…”

Section: Governing Equationsmentioning

confidence: 99%

Numerical Study of Heat Transfer Intensification in a Circular Tube Using a Thin, Radiation-Absorbing Insert. Part 2: Thermal Performance

Jasiński

2021

Energies

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This article is the second part of the work under the same title, which is based on the results of the research presented in the previous article: “Numerical study of heat transfer intensification in a circular tube using a thin, radiation-absorbing insert. Part 1: Thermo-hydraulic characteristics”. Part 1 presents an analysis of pressure drops and heat transfer intensification in a round tube with an insert, using the phenomenon of radiation absorption. In this paper, an analysis of the tested insert’s thermal performance (PEC) is presented, taking into account the criterion of equal pumping power. The tests were carried out for the range of Re = 5000–100,000 numbers, for various insert diameters (from 20% to 90% of the pipe diameter) and a constant temperature difference between the wall and the gas ∆T = 100 °C. The highest Nu numbers were observed for inserts with dimensionless diameters of 0.3 and 0.4, while the highest flow resistance was observed for inserts with diameters of 0.6 and 0.7 of the channel diameter. The thermal efficiency was calculated in two ways, as was the associated Nu number. These results significantly differed from each other: the maximum PEC values for method (I) reached 2, and for method (II) to 8. The common feature for both calculation methods was the fact that the maximum values of the Nu number and the thermal efficiency were observed for small Re numbers; however, as the Re number increases, PEC and Nu number decrease strongly.

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“…This flow pattern exists in the tested inserts. Jasiński and Menter made a detailed analysis of this model in References [21,23]. The SST model includes two transport equations: Turbulence kinetic energy:…”

Section: Governing Equations and Boundary Conditionsmentioning

confidence: 99%

“…The results disclosed the effect of different ball diameters on the thermo-hydraulic characteristics of water and air flow through a vertical tube, suggesting that the turbulence level around the spherical nodes increased and accordingly the flow velocity of fluid between the nodes and tube wall was greatly improved. Jasiński [20][21][22] used numerical methods to look into the characteristics of heat transfer, pressure drop, and thermal performance in a BT-based circular tube at a large Reynolds number ranging from 10,000 to 300,000. The computational results indicated that the use of BTs yielded a higher heat transfer rate with the increase of the Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer and Friction Characteristics of Turbulent Flow through a Circular Tube with Ball Turbulators

et al. 2018

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Abstract:One of the most commonly used methods of heat transfer enhancement is flow turbulization. This effect can be achieved, e.g., by placing special turbulizing elements into the channel. In this paper, the effects of ball turbulators (BTs) on the heat transfer and fluid friction characteristics in a circular tube are investigated through numerical simulation. The Reynolds number (Re) is in the range of 5000-35,000 under a condition of uniform heat-flux. BTs with different diameter ratios (e.g., 0.5, 0.75, and 1) and spacer lengths (40, 51.77, and 62.5 mm) are inserted in the circular tubes. The results show that the heat transfer rates in the tube equipped with BTs are around 1.26-2.01 times that of those in the plain tube. The BTs with a ball diameter ratio of one provide higher friction factors than 0.75 and 0.5 by about 34.6-46.2% and 51.1-63.4%, respectively. A smaller ball diameter ratio is more able to decrease the friction factor. The performance evaluation criterion (PEC) data indicate that the use of a smaller ball diameter ratio (BDR) and a smaller spacer length are preferred. The results also reveal that BTs with a larger diameter ratio and a smaller spacer length yield the highest heat transfer rate as well as the largest pressure loss. Compared with the plain tube, the fluid flow velocity near the tube wall is significantly improved when BTs are used at the same Reynolds number.

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Numerical study of the thermo-hydraulic characteristics in a circular tube with ball turbulators. Part 2: Heat transfer

Cited by 22 publications

References 10 publications

Study of the Influence of the Lack of Contact in Plate and Fin and Tube Heat Exchanger on Heat Transfer Efficiency under Periodic Flow Conditions

Study of the Influence of the Lack of Contact in Plate and Fin and Tube Heat Exchanger on Heat Transfer Efficiency under Periodic Flow Conditions

Numerical Study of Heat Transfer Intensification in a Circular Tube Using a Thin, Radiation-Absorbing Insert. Part 2: Thermal Performance

Heat Transfer and Friction Characteristics of Turbulent Flow through a Circular Tube with Ball Turbulators

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