Computational Fluid Dynamics (CFD)
S. Akbarnejad; M. Ziabasharhagh
Abstract
This paper presents a novel 1D modeling approach to optimize steam ejector entrainment ratios, introducing new definitions of ejector efficiency and enhancement methods. Using the proposed model, an ejector is tailored for specific boundary conditions with available computational fluid mechanic ...
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This paper presents a novel 1D modeling approach to optimize steam ejector entrainment ratios, introducing new definitions of ejector efficiency and enhancement methods. Using the proposed model, an ejector is tailored for specific boundary conditions with available computational fluid mechanic results for validation. Dimensional and geometrical parameters are computed from the theoretical 1D model, and various geometries are explored using computational fluid mechanic to determine entrainment ratios. Innovative definitions of ejector efficiency are introduced. The first definition compares the entrainment ratio of the ejector to a system comprising a steam compressor, turbine, and mixer, yielding an efficiency of 13.5% under specified conditions. The second, more practical definition calculates the maximum achievable entrainment ratio, disregarding frictional losses, resulting in an efficiency of 70%. An algorithm is proposed to optimize ejector dimensions to approach this maximum. Using this algorithm, the optimum throat diameter was determined through computational fluid mechanic analysis, demonstrating an increase in the entrainment ratio from 0.7 to 1.25. The theoretical maximum value calculated by the 1D model is 1.282, indicating that 97.7% of the theoretical maximum was achieved in computational fluid mechanic simulations. This highlights the significant improvement in the entrainment ratio using the 1D model and delineates its limit under given conditions. The third definition establishes the theoretical maximum entrainment ratio given specific boundary conditions and dimensions, assuming no losses in the nozzle, mixing process, or diffuser; yielding an efficiency of 81% for the same ejector studied.
Computational Fluid Dynamics (CFD)
Aydin Zabihi; Nader Pourmahmoud
Abstract
Cooling tubes are inserted into the desiccant dehumidifier liquid of a 3-fluid liquid-to-air membrane energy exchanger (LAMEE) to regulate the temperature of the dehumidifier liquid. As a result, the 3-fluid LAMEE's performance is significantly influenced by the refrigerated tubes. The numerical ...
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Cooling tubes are inserted into the desiccant dehumidifier liquid of a 3-fluid liquid-to-air membrane energy exchanger (LAMEE) to regulate the temperature of the dehumidifier liquid. As a result, the 3-fluid LAMEE's performance is significantly influenced by the refrigerated tubes. The numerical analysis of the present work shows that the number of chilled tubes and their inner diameter affect the effectiveness (total, latent, and sensible) rate of moisture removal, adequate cooling power, and exergy loss. Additionally, the dehumidifier liquid channel receives the addition of wavy cooling tubes for the first time. The relationship between wave height and wave length is known as wave steepness and its impact on efficiency and energy loss is also examined. Numerical studies show that the number and inner diameter of the cooling tubes have a direct correlation with the efficiency of the 3-fluid LAMEE. The improved the efficiency, the more cooled tubes there are and the larger their diameter. Furthermore, both exergy loss and without dimensions exergy loss increase with the quantity and diameter of refrigerated tubes. The sensible and latent effectiveness of the 3-fluid LAMEE is increased by the wavy refrigeration tubes as compared to straight tubes; the augmentation of the sensible and latent effectiveness increases with wave steepness.
Fluid Mechanics
M. Alemi; R. Maia
Abstract
The present study aimed to investigate two numerical solutions of the Navier-Stokes equations. For this purpose, the mentioned flow equations were written in two different formulations, namely (i) velocity-pressure and (ii) vorticity-stream function formulations. Solution algorithms and boundary conditions ...
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The present study aimed to investigate two numerical solutions of the Navier-Stokes equations. For this purpose, the mentioned flow equations were written in two different formulations, namely (i) velocity-pressure and (ii) vorticity-stream function formulations. Solution algorithms and boundary conditions were presented for both formulations and the efficiency of each formulation was investigated by considering a two-dimensional low laminar flow around a square pile in a rectangular computational domain. Simulations under the same conditions were conducted to assess the difference between results generated by both formulations. Furthermore, the accuracy of the results was analyzed through a comparison of the results with the available reference data. In addition, computational efficiency of both formulations was investigated in term of computation time. The corresponding results indicated that both formulations are adequate to the case used in the present study. Moreover, performed simulations showed that solving the vorticity-stream function form of the flow equations is faster than solving the velocity-pressure form of those equations for simulating a two-dimensional laminar flow around a square pile.
