Browsing by Author "Nguyen Van Vu"

Now showing 1 - 8 of 8
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    Applying a variable geometry ejector in a solar ejector refrigeration system
    (Elsevier BV, 2020-01-01) Nguyen Van Vu; Dvořák Václav
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    CFD simulation of ejector: is it worth to use real gas models?
    (EDP Sciences, 2018-01-01) Nguyen Van Vu; Kracík Jan
    This paper presents progress of evaluation existing ejector of previous work with different gases, included real gas. This work was done by the Ansys simulation tool. The paper also discussed about the two solvers used for simulating real gas difluoromethane (R32). The results showed that entrainment ratios are almost not influenced by different gases but by the working conditions. Secondly, the solver pressure-based can obtain comparable results with the density-based one, while it is much more stable and solution converges faster than the density-based.
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    Evaluating the moisture transfer of membranes for total heat exchanger
    (2017-01-01) Nguyen Van Vu; Dvořák Václav
    This paper presents an experimental evaluation of moisture transfer of a novel membrane which is used in enthalpy heat exchanger. The moister transfer through a membrane was investigated in a model of counter flow heat exchanger and the effectiveness of moister transfer was evaluated for various flow velocities. It was found that the measuring error, i.e. difference between moister absorbed and released is quite high. Therefore, measuring uncertainty analyses were performed. The resulting uncertainty of effectiveness of moister transfer was derived using partial derivatives of all influencing quantities and considering both random and systematic uncertainties. It was found that measuring of mass flow rate has the biggest influence on resulting uncertainty of moister transfer effectiveness. Therefore, accuracy of measured air flow rates measuring must be improved to reach lower resulting uncertainty.
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    Experimental and Numerical Study on Supersonic Ejectors Working with R-1234ze(E)
    (EDP Sciences, 2018-01-01) Kracík Jan; Dvořák Václav; Nguyen Van Vu; Smierciew Kamil
    These days, much effort is being put into lowering the consumption of electric energy and involving renewable energy sources. Many engineers and designers are trying to develop environment-friendly technologies worldwide. It is related to incorporating appropriate devices into such technologies. The object of this paper is to investigate these devices in connection with refrigeration systems. Ejectors can be considered such as these devices. The primary interest of this paper is to investigate the suitability of a numerical model for an ejector, which is incorporated into a refrigeration system. In the present paper, there have been investigated seven different test runs of working of the ejector with a working fluid R-1234ze(E). Some of the investigated cases seem to have a good agreement and there are no significant discrepancies between them, however, there are also cases that do not correspond to the experimental data at all. The ejector has been investigated in both on-design and off-design working modes. A comparison between the experimental and numerical data (CFD) performed by Ansys Fluent software is presented and discussed for both an ideal and a real gas model. In addition, an enhanced analytical model has been introduced for all runs of the ejector.
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    HFO1234ze(e) As an Alternative Refrigerant for Ejector Cooling Technology
    (MDPI AG, 2019-01-01) Nguyen Van Vu; Varga Szabolcs; Dvořák Václav
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    Influence of number and thickness of blades on the performance of centrifugal fans
    (MDPI AG, 2020-01-01) Nguyen Van Vu; Dvořák Václav; Elbarghthi Anas
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    Low-Density Geopolymer Composites for the Construction Industry
    (MDPI, 2022-01-01) Louda Petr; Nguyen Van Vu; Le Van Su; Buczkowska Katarzyna Ewa; Lós Piotr; Růžek Vojtěch
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    Property evaluation of membranes for total heat exchanger
    (Technická universita v Liberci, 2015-01-01) Nguyen Van Vu