Numerical study of the thermo-hydraulic characteristics in a circular tube with ball turbulators. Part 1: PIV experiments and a pressure drop

Jasiński, Piotr Bogusław

doi:10.1016/j.ijheatmasstransfer.2014.02.074

Cited by 13 publications

(8 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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%

“…Due to the fact that for such geometries, the velocity field structure is not very complicated and similar to the flow in a smooth pipe; therefore, the computational grid is also simple. Only in the near-wall laminar sublayer areas, i.e., at the channel wall and on both sides of the insert, the mesh was additionally densified to obtain the appropriate y + value, which for the used SST k-ω turbulence model should not exceed 2 [2,16,17,21,22]. Nevertheless, validation for numerical results was done, but for slightly different flow channel shapes and presented in papers [16,19,23].…”

Section: Grid Independencementioning

confidence: 99%

“…To calculate the friction factor for a smooth pipe, the Blassius formula was used: Nevertheless, validation for numerical results was done, but for slightly different flow channel shapes and presented in papers [16,19,23].…”

Section: Data Processingmentioning

confidence: 99%

See 2 more Smart Citations

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

Jasiński

2021

Energies

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Boundary Conditions Of Simulation and Numerical Modelmentioning

confidence: 99%

Section: Grid Independencementioning

confidence: 99%

See 1 more Smart Citation

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

Jasiński

2021

Energies

Self Cite

View full text Add to dashboard Cite

show abstract

“…The numerical studies for Re = 9100-17,400 and the attack angles of 30 • , 50 • , and 70 • allowed one to determine values of the Nusselt number, friction factor, and thermal performance factor, which increased with an increasing value of attack angle. Jasiński [3][4][5] conducted experimental and numerical investigations of a flow in the circular tube with ball turbulators. The investigations for different diameters of the balls, different distances between them, and Re = 10,000-300,000 were carried out.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Thermal-Flow Characteristics of Pipes with Helical Micro-Fins of Variable Height

et al. 2021

Self Cite

View full text Add to dashboard Cite

The results of numerical investigations of heat transfer and pressure drops in a channel with 30° helical micro-fins are presented. The main aim of the analysis is to examine the influence of the height of the micro-fins on the heat-flow characteristics of the channel. For the tested pipe with a diameter of 12 mm, the micro-fin height varies within the range of 0.05–0.40 mm (with 0.05 mm steps), which is equal to 0.4–3.3% of its diameter. The analysis was performed for a turbulent flow, within the range of Reynolds numbers 10,000–100,000. The working fluid is water with an average temperature of 298 K. For each tested geometry, the characteristics of the friction factor f(Re) and the Nusselt number Nu(Re) are shown in the graphs. The highest values of Nusselt numbers and friction factors were obtained for pipes with the micro-fins H = 0.30 mm and H = 0.35 mm. A large discrepancy is observed in the friction factors f(Re) calculated from the theoretical relationships (for the irregular relative roughness values shown in the Moody diagram) and those obtained from the simulations (for pipes with regular roughness formed by micro-fins). The PEC (Performance Evaluation Criteria) heat transfer efficiency analysis of the geometries under study is also presented, taking into account the criterion of the same pumping power. The highest PEC values, reaching 1.25, are obtained for micro-fins with a height of 0.30 mm and 0.35 mm and with Reynolds numbers above 40,000. In general, for all tested geometries and for large Reynolds numbers (above 20,000), the PEC coefficient reaches values greater than 1, while for lower Reynolds numbers (less than 20,000), its values are less than 1.

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

Numerical study of the thermo-hydraulic characteristics in a circular tube with ball turbulators. Part 1: PIV experiments and a pressure drop

Cited by 13 publications

References 17 publications

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

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

Investigation of Thermal-Flow Characteristics of Pipes with Helical Micro-Fins of Variable Height

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

Contact Info

Product

Resources

About