Mathematical model to analyze the flow and heat transfer problem in U-shaped geothermal exchangers

Egidi, Nadaniela; Giacomini, Josephin; Maponi, Pierluigi

doi:10.1016/j.apm.2018.03.024

Cited by 20 publications

(9 citation statements)

References 11 publications

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“…However, the local circumferential average Nusselt number was not estimated accurately by the existing correlation. More recent studies by Cvetkovski et al [25], Egidi et al [26], Safari et al [27], and Pan et al [28] revealed the characteristics of turbulent heat transfer in curved pipes.…”

Section: Introductionmentioning

confidence: 97%

“…Therefore, it is difficult to analyze the characteristics of the internal circumferential temperature fields. Besides, in the abovementioned studies, the constant wall temperature thermal boundary condition was used by Mori and Nakayama [11,13], Zapryanov et al [15], Xin and Ebadian [16], Di Piazza and Ciofalo [17], Liberto et al [18], Cvetkovski et al [26], and Pan et al [29]. The constant wall heat flux thermal boundary condition was used by Mori and Nakayama [12], Cheng and Akiyama [14], Kang and Yang [19], Arvanitis et al [20], Wang et al [23], and Safari et al [28].…”

Section: Introductionmentioning

confidence: 99%

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Experimental Study and Conjugate Heat Transfer Simulation of Turbulent Flow in a 90° Curved Square Pipe

et al. 2020

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This paper discusses the turbulent flow and heat transfer from a uniform air flow with high temperature to the outside through a 90° curved square pipe. Both conjugate heat transfer (CHT) simulation and experiments of temperature field measurements at cross sections of the pipe are performed. A straight pipe is investigated and compared with the 90° curved pipe. The temperature of the air flow at the inlet of the pipe is set at 402 K, and the corresponding Reynolds number is approximately 6 × 104. To obtain the spatial average temperature at each cross section, the temperature fields are measured along the streamwise of the pipes and in the circumferential direction using thermocouples at each cross section from the inlet to the outlet of both the straight and curved pipes. Furthermore, the simulation is performed for turbulent flow and heat transfer inside the pipe wall using the Re-normalization group (RNG) k-ε turbulence model and CHT method. Both the experimental and numerical results show that the curvature of the pipe result in a deviation and impingement in the high-temperature core and a separation between the wall and air, resulting in a secondary flow pattern of the temperature distribution.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Experimental Study and Conjugate Heat Transfer Simulation of Turbulent Flow in a 90° Curved Square Pipe

et al. 2020

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“…Steam condensation requires a heat exchanger, the design of which makes this element the most demanding and expensive part of the condensation hood. For this reason, the investigation of such appliances in terms of heat transfer and condensation efficiency was necessary [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Experimental analysis and development of an in-house CFD condensation hood model

et al. 2021

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An existing condensation hood has been numerically investigated using k-ε turbulence and species transport models. Due to the geometrical complexity of the appliance, two additional mathematical models were introduced with the use of User Defined Functions (UDFs). They were a model of a fan and a model of the internally finned pipes of a heat exchanger. The latter also involved a condensation model of steam implemented by mass and energy source terms. Such an approach allowed us to avoid troublesome two-phase flow simulation and thus significantly reduced the computational effort. Based on the results provided by the numerical model, potential improvements of the heat exchanger were proposed and implemented into a second, modified numerical model. Reduction of the number of the pipes by 25% is the most important change of the developed device. Its negative effect on condensation efficiency was to be compensated by improvements of steam flow in the device. Once the modifications had been evaluated, the prototype of the device was built and tested experimentally. Both the numerical and experimental results agree and show that, the modified condensation hood is comparable to the original construction in terms of condensation efficiency, despite the significant heat transfer surface area reduction.

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“…There has been a lot of research on the natural frequency of single straight or curved pipes considering fluid-structure interaction (FSI). [1][2][3][4][5][6] MP Paidoussis 1 and MP Paidoussis and NT Issid 2 made a detailed study in his monographs on linear and nonlinear dynamics of the fluid-conveying pipes. HB Wen et al 3 proposed a kinetic model of the straight-curved pipe conveying fluid.…”

Section: Introductionmentioning

confidence: 99%

“…YJ Hu and WD Zhu 4 established a dynamic model of an extensible fluid-conveying curved pipe with an arbitrary undeformed configuration. N Egidi et al 5 proposed a mathematical model for Ushaped geothermal heat exchangers based on the unsteady Navier-Stokes problems. Many researchers studied the in-plane and out-of-plane vibration modes of the curved pipe based on the total extensible and inextensible assumption.…”

Section: Introductionmentioning

confidence: 99%

Resonance risk and global sensitivity analysis of a straight–curved combination pipe based on active learning Kriging model

Zhao

Liu

Guo

et al. 2019

Advances in Mechanical Engineering

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The resonance failure of straight-curved combination pipes conveying fluid which are widely used in engineering is becoming a serious issue. But there are only few studies available on the resonance failure of combination pipes. The resonance failure probability and global sensitivity analysis of straight-curved combination pipes conveying fluid are studied by the active learning Kriging method proposed in this article. Based on the Euler-Bernoulli beam theory, the dynamic stiffness matrices of straight and curved pipes are derived in the local coordinate system, respectively. Then the dynamic stiffness matrix and characteristic equation of a straight-curved combination pipe conveying fluid are assembled under a global coordinate system. The natural frequency is calculated based on the characteristic equation. A resonance failure performance function is established based on the resonance failure mechanism and relative criterions. The active learning Kriging model based on expected risk function is introduced for calculating the resonance failure probability and moment-independent global sensitivity analysis index. The importance rankings of input variables are obtained with different velocities. According to the results, it is shown that the method proposed in this article provides a lot of guidance for resonance reliability analysis and anti-resonance design in combination pipes conveying fluid.

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Mathematical model to analyze the flow and heat transfer problem in U-shaped geothermal exchangers

Cited by 20 publications

References 11 publications

Experimental Study and Conjugate Heat Transfer Simulation of Turbulent Flow in a 90° Curved Square Pipe

Experimental Study and Conjugate Heat Transfer Simulation of Turbulent Flow in a 90° Curved Square Pipe

Experimental analysis and development of an in-house CFD condensation hood model

Resonance risk and global sensitivity analysis of a straight–curved combination pipe based on active learning Kriging model

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