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Numerical simulation to study fluid flow and heat transfer characteristics of conical spiral tube
Published in Alka Mahajan, Parul Patel, Priyanka Sharma, Technologies for Sustainable Development, 2020
This study shows that high velocity region changes the angular position at cross section base on coil orientation velocity and curvature. At this location high values of Nu can be observed. This study shows that orientation of coil tube changes the location of high velocity region and high heat transfer. This can contribute to design conical spiral tube based heat exchangers.
Development of a fully planar logarithmic spiral antenna with integrated balun in UWB GPR systems for landmines detection
Published in Electromagnetics, 2022
Narek Grigoor-Feghi, Reza Masoumi, Robab Kazemi
Antenna is a key element of any GPR system. Currently, the antennas, which have been used in GPR systems include horn (Ahmed et al. 2015), bow-tie (Serhir and Lesselier 2018), logarithmic spiral (He and Akizuki 2010; Kazemi 2018; Richardson et al. 2020), slot spiral (Patnaik, Arunachalam, and Krishnamurthy 2016), conical spiral (Yao, Liu, and Georgakopoulos 2017), and Vivaldi (Takach et al. 2016) antennas. In general, it has been shown that logarithmic spiral antenna is often a good candidate for detection systems due to its planar structure and frequency-independent performance. Furthermore, the spiral antenna radiates circularly polarized waves, which is a major advantage over linearly polarized antennas. However, the high input characteristic impedance and the need for balanced feeding structure are the challenges in practical implementation of spiral antennas. A balun is required to transform the signals from an unbalanced feed line (e.g., coaxial cable) to a balanced spiral arm. In recent years, a number of wideband baluns, such as a tapered microstrip to a parallel strip line (Chen et al. 2020; Chen, Zhang, and Xu 2020; Jastram and Filipovic 2018; Sakomura et al. 2018; Singh and Deshpande 2017), coplanar waveguide to coplanar stripline balun (Thaysen, Jakobsen, and Appel Hansen 2000; Tilley, Wu, and Chang 1994), and Vivaldi-shaped balun (Yoo et al. 2019) have been reported. However, most of the configurations are vertically connected to the antenna, which makes the antenna bulky and frail or have limited bandwidth.
Multiphysics field coupling simulation for shell-and-tube heat exchangers with different baffles
Published in Numerical Heat Transfer, Part A: Applications, 2020
Juan Xiao, Simin Wang, Shupei Ye, Jian Wen, Zaoxiao Zhang
Fluid–structure interaction has been mainly applied to sedimentation, turbulence, aerodynamic, bio-fluid and bio-mechanics [36]. The effects of different loads on structural stress and end side displacement load of “L”-type large-diameter buried pipe were investigated based on thermal fluid-structure coupling [37, 38]. Yan et al. [39] proposed a method of heat transfer enhancement for elastic tube bundle heat exchangers by flow induced vibration and used FSI to show the influence of tube-side flow velocity on natural frequency at different mode order for conical spiral tube bundle. Zhang et al. [40] presented results of heat transfer coefficient, j f−1 factor, temperature and stress distribution at different fin thicknesses and fin offsets for plate-fin heat exchangers. Liu et al. [41] studied the effect of temperature dependent viscosity on complicated flow characteristics of hydrodynamic torque converter and obtained the equivalent stress and deformation by thermal FSI. Therefore, FSI solver has been regarded as an effective method to offer flexibility, accuracy and breadth for practical applications [42].
Effect of Swirl on Thermal and Hydraulic Properties of Ice Slurry Flow
Published in Heat Transfer Engineering, 2021
Hazhir Ahmadkermaj, Reza Maddahian, Mehdi Maerefat
Flow and heat transfer characteristics of other phase change material slurries like phase change emulsion, clathrate hydrate slurry, and microencapsulated phase change material slurry (MPCM) in circular pipes, were measured experimentally [15–18] and investigated numerically [19–21]. The velocity, temperature profiles, and heat transfer data of MPCM in various configurations including conical spiral, in-plane spiral, and helical spiral of square cross section tubes were investigated by Kurnia et al. [20]. The numerical results showed that for the laminar flow of MPCM suspension, heat transfer performance improved by increasing the concentration of MPCM from 1% to 10% but, the pressure drop of suspension and the consumed pumping power increased and worsened.