International Journal of Thermofluid Science and Technology

862 KB

Open AccessArticle

Impact of wall electrical conductivity on heat transfer enhancement in MHD hybrid nanofluid flow within an annulus

by Ali Bendjaghlouli, Brahim Mahfoud and Hibet Errahmane Mahfoud

Int. J. Thermofluid Sci. Technol. 2024, 11(2), 110204; https://doi.org/10.36963/IJTST.2024110204 - 5 Jun 2024

Cited by 3 | Viewed by 72

A numerical investigation was conducted to explore the influence of magnetic field and the electric conductivity of container walls on the swirling flow of a hybrid nanofluid. In this study, a stationary inner wall and a rotating outer wall with a fixed Ω were considered within the annular between coaxial cylinders. Radial application of a magnetic field was utilized to assess its impact on the average Nusselt number. The mathematical model, formulated by differential equations, was solved using the finite volume method. The study examined the variations in azimuthal velocity, temperature, and Nusselt number with increasing magnetic intensity. Therefore, it can be concluded that the control of heat transfer efficiency increasingly relies on the combined influence of magnetic field intensity and the electrical conductivity of walls. The findings revealed that higher magnetic Hartmann numbers led to elevated temperature distribution and azimuthal velocity within the annulus center. Moreover, electromagnetic damping exhibited a more pronounced impact on heat transfer when all walls were electrically conductive, resulting in a 90% improvement in heat transfer with the hybrid nanofluid. Full article

► Show Figures

Figure 1

1739 KB

Open AccessArticle

Thermal-hydrodynamic analysis for internally finned tubes: Experimental, numerical and performance evaluation study

by O. H. Salem, Ahmed Hegazy and K. Yousef

Int. J. Thermofluid Sci. Technol. 2024, 11(2), 110203; https://doi.org/10.36963/IJTST.2024110203 - 28 May 2024

Cited by 1 | Viewed by 72

Abstract

The characteristics of heat transfer and fluid flow of an internally continuously finned tube were studied, experimentally and numerically, and a performance evaluation study was conducted. The numerical results were validated with the current experimental data as well as other published data, with a maximum deviation of 4.65%. The effect of different key parameters like fin height, number of fins, and fin thickness on the thermal-hydrodynamic performance was studied. The study reveals that increasing both fin height, which is the most effective parameter, and number of fins raises the heat transfer coefficient and friction factor values, but fin thickness negligibly affects the performance. Notably, the average heat transfer coefficient and friction factor values rise by 40.92 % and 18.4 %, respectively, if the fin height to diameter ratio is increased from 0.1786 to 0.4018, and by 35.4 % and 13.5 %, respectively, if the number of fins is increased from 2 to 6, compared to smooth tubes under a mass flow rate of 0.3 kg/s. Furthermore, the thermal enhancement factor, which is the ratio between the heat transfer coefficient and friction factor for the enhanced tube as opposed to the smooth one, increases by 33.27%, 48.64%, and 8.71% if the fin height, number of fins, and fin thickness increase by 125%, 300%, and 200%, respectively, under constant mass flow rate condition. While the thermal enhancement factor decreases by 22.89%, 74.53%, and 7.92% if the fin height, number of fins, and fin thickness increase by 125%, 300%, and 200%, respectively, under constant pressure drop condition. In the case of constant pumping power condition, the thermal enhancement factor hovers around unity for fin height and thickness, and it decreases by 23.89% if the number of fins increases by 300%. Full article

► Show Figures

Figure 1

1671 KB

Open AccessArticle

Numerical study of natural convection of Bingham fluid using a flexible fin

by Hanaa Derraz, Bouzit Mohamed, Mokhefi Abderrahim, Bencherif Atika and Meriem Toumi

Int. J. Thermofluid Sci. Technol. 2024, 11(2), 110202; https://doi.org/10.36963/IJTST.2024110202 - 23 Apr 2024

Cited by 1 | Viewed by 76

Abstract

This research focuses on the analysis of the flow and heat transfer inside a square cavity containing a Bingham plastic fluid. The cavity undergoes heating on its left side, where a flexible and elastic fin is positioned at the center of this heated wall. Cooling takes place on the right side of the cavity, while the upper and lower walls are wellinsulated. The equations governing the complex interaction between the fluid and the flexible fin are accurately solved using an arbitrary Lagrangian-Eulerian approach, in conjunction with the finite element methodology. This study concentrates on the impact of the flexible fin on heat transfer in the context of unsteady natural convection of a complex fluid with a yield stress inside a square cavity. The considered parameters include the variation of the Rayleigh number in the range of 10³ to 10⁵, the modification of the elasticity modulus between 5×10¹⁰ and 5×10¹¹, the fin length (Lc) from 0.004 to 0.0073, the Prandtl number (Pr) from 0.71 to 100, and the variation of the Bingham number from 0 to 20. To provide a comprehensive understanding of the observed thermal and fluidic phenomena, results will be displayed in the form of isothermic contours and streamlines, accompanied by Nusselt number (Nu) and maximum stress (σ_max) curves. Observations indicate a significant improvement in the Nusselt number in the absence of a yield stress (Bn = 0), reaching its maximum at (Ra = 10⁵). Conversely, the variation of the elasticity modulus shows negligible influence. As the yield stress (Bn) increases, it begins to dominate the flow by nullifying the buoyancy-induced current, reaching a constant value for (Bn = 20), corresponding to the conduction limit. Full article

► Show Figures

Figure 1

1373 KB

Open AccessArticle

Energetic performance investigation of ejector air conditioning cycles using the environment friendly gas R161 (Fluoroethane) as substitute to the phase-out R22 (Chlorodifluoromethane)

by Youcef Maalem and Hakim Madani

Int. J. Thermofluid Sci. Technol. 2024, 11(2), 110201; https://doi.org/10.36963/IJTST.2024110201 - 12 Apr 2024

Viewed by 99

Abstract

The present research aims to conduct a comparative examination between two refrigerants, the phase-out R22, and the new ecofriendly R161. They were used in two different ejector air conditioning cycles (Standard ejector cycle (SEC) and Modified ejector cycle (MEC)) under a wide range of working conditions. A numerical simulation has been carried out with MATLAB simulation code through the thermodynamic energy analysis to explore various thermodynamic performances ((primary (m_pf) and secondary (m_sf) mass flow rate), entrainment ratio (μ), pressure lift ratio (PLR), refrigeration effect (Q), compressor work (W) and coefficient of performance (COP)) of SEC and MEC working with both refrigerants under the same operating temperatures (condensing temperature (T_cond) varies from (30 to 55) °C and evaporating temperature (T_evap) varies from (-10 to 10) °C). The tests show that under the same given operating temperatures, the (m_pf and m_sf), COP, μ and PLR of R161 are close to those obtained with R22 in both cycles. Moreover, it has been proved that MEC has a higher Q and COP than SEC. On the other hand, the thermodynamic analysis revealed that as T_cond increases, (m_sf, μ, Q and COP) decreases, and (m_pf, PLR and W) increases. However, as T_evapincreases, the (m_sf, μ, Q and COP) increases and (m_pf, PLR and W) decreases. Overall, the simulated results confirm that R161 can be useful for air conditioning applications and can serve as a good alternative for the phase-out R22. Full article

► Show Figures

Figure 1

Journal Menu

Journal Browser

Int. J. Thermofluid Sci. Technol., Volume 11, Issue 2 (04 2024) – 4 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI