International Journal of Thermofluid Science and Technology

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Study of the performances of an ejector refrigeration cycle using CO₂-based mixtures in subcritical and transcritical mode

by Chaabane Abdou, Hakim Madani and Abdelmalek Hasseine

Int. J. Thermofluid Sci. Technol. 2023, 10(3), 100304; https://doi.org/10.36963/IJTST.2023100304 - 2 Sep 2023

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Abstract

The negative impact of actual refrigerants on the environment urged conduct to search for new refrigerants with low global warming potential (GWP). CO₂ is one of the promising alternatives; however, its thermodynamic properties impose a transcritical cycle that has a low energy efficiency. In the present study, a simulation program was developed to investigate the performances of an ejector refrigeration cycle working with three CO₂-based mixtures: (CO₂+R290), (CO₂+R1234yf), and (CO₂+R600a) according to subcritical mode and (CO₂+R116) under transcritical mode. The addition of other pure compounds to CO₂ displaces the critical point and modifies the phase equilibrium lines resulting in a reduction in operating pressures and an increase in the energy efficiency of the refrigeration cycle. Simulation results showed that the Suction Nozzle Pressure Drop (SNPD) has a significant impact on the performance of the cycle and has no effect on the entrainment ratio of the ejector. Moreover, it was found that there is an optimal SNPD which gives maximum COP and pressure recovery. It was also noticed that the maximum performance of the refrigeration cycle with a subcritical ejector depends on the evaporation and the condenser temperatures. Full article

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Blood flow transport with electrokinetic flow technique through a narrow semicircle shape within the vertical 2D asymmetrical model

by Suwimon Saneewong Na Ayuttaya

Int. J. Thermofluid Sci. Technol. 2023, 10(3), 100303; https://doi.org/10.36963/IJTST.2023100303 - 15 Jul 2023

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Abstract

Within the vertical 2-Dimensional (2D) asymmetrical model, the blood flow transport through a narrow semicircle shape is the numerical study based on the concept of the electrokinetic flow technique. In this study, the blood flow transport has been compared to the electric field, the flow pattern, the pressure field, the vorticity, the temperature field, and the concentration field with and without the electrokinetic flow. The electrical voltage and time are varied from 0 – 20 kV and 0 – 1 s, respectively. The result has shown that the blood flow transport is moved upward within the vertical 2D asymmetrical model and the electric field has not appeared in the case of without the electrokinetic flow. With the electrokinetic flow, the flow pattern, the pressure field, the vorticity field, the temperature field, and the concentration field are not the same pattern as the electric field but they are induced by the electric field. Furthermore, at the center of a narrow semicircle shape, the electric value, the velocity, and the pressure are increased with the electrical voltage increasing but the vorticity and concentration are decreased with the electrical voltage increasing. Finally, the experimental result is compared with the numerical result, it can be seen that simulation results had good agreement with experiment results. Full article

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Influence of variable viscosity and gravity fluctuation on double diffusive convection in a fluid layer with boundary slab of finite conductivity

by Gangadharaiah Y H and Nagarathnamma H

Int. J. Thermofluid Sci. Technol. 2023, 10(3), 100302; https://doi.org/10.36963/IJTST.2023100302 - 14 Jul 2023

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Abstract

The linear stability analysis is carried out for the onset of doublediffusive convection in a fluid layer with a boundary slab along with temperature-dependent viscosity and gravity fluctuation. The authors proposed three types of gravity fluctuation. We considered three cases of gravity field fluctuation: (a) linear and (b)parabolic and (c) cubic. An analytical solution for the subsequent problem is acquired through the perturbation technique. The findings demonstrate that the viscosity variation parameter, the thermal conductivity ratio, the gravity parameter, the depth ratio, and the soret parameter accelerate the start of convection, while the increasing Lewis number slow down the convective motion. Additionally, the system was found to be more stable for the linear type of gravity field fluctuation and more unstable for the cubic type of gravity field fluctuation. Full article

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Finite element analysis for electro-osmotic Erying-Powell fluid flow past a stretching sheet with an exponential heat source - an ANN approach

by S. Ramprasad, Nagabhushana Pulla and Y. S. Kalyan Chakravarthy

Int. J. Thermofluid Sci. Technol. 2023, 10(3), 100301; https://doi.org/10.36963/IJTST.2023100301 - 25 Jun 2023

Cited by 1 | Viewed by 37

Abstract

This paper gives the numerical analysis for an electro-osmotic Eyring-Powell fluid flow that is in two dimensions along a stretched sheet. The modified governing equations are resolved by the finite element technique. Graphs are used to display the various properties for several relevant factors on dimensionless velocity and temperature fields. The results are compared with previous findings in order to confirm the accuracy of the numerical solution. There appears to be a decrease in velocity when the magnetic parameter and Eckret number increase. This study has implications for fluidization, environmental pollutants, and agriculture. In this study, computational fluid dynamics (CFD) simulations and an artificial neural network (ANN) model are both employed. Full article

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Int. J. Thermofluid Sci. Technol., Volume 10, Issue 3 (06 2023) – 4 articles

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