No abstract

No abstract

No abstract

Low-frequency wideband noise reduction has posed a significant problem to the scientific and technical communities in recent years. A single layer of a parallel-arranged inhomogeneous micro-perforated panel (iMPP) coupled with spider-web designed cavities is offered as a composite acoustic structure in this paper. Three different spider-web shapes have been designed and studied, i.e. circular, octagonal, and square. By controlling the different inhomogeneous patterns, perforation ratio, the thickness of iMPP, and back cavity depths, a broader multipeak low-frequency sound-absorbing performance equivalent to different resonant frequencies can be achieved. To anticipate the sound absorption coefficient of the new design, both theoretical analysis and finite-element method (FEM) simulation are executed. The predicted and FEM simulation sound absorption results of the new composite structure are verified in the experimental investigation using a square-designed sound impedance tube. By a subwavelength thickness of just 100 mm, a highly effective low-frequency broadband sound-absorbing composite structure is successfully attained by integrating many inhomogeneous MPP unit cells supported with spider-web-designed cavities. The average sound absorption coefficient is over 90% ( α = 0.94) within the bandgap of 230 Hz to 470 Hz. Compared to traditional sound-absorbing materials, the composite structure comprises inhomogeneous MPP coupled with spider-web-designed cavities, which may provide good absorption performance while maintaining a modest and robust construction for active low-frequency noise suppression.

No abstract

Shell and tube heat exchanger (STHX) is an implement that has tremendous applications in numerous industrial processes and research areas. In this study, the commercial software ANSYS is used for 3-D computational fluid dynamics (CFD) to compare the thermo-hydraulic performance of STHXs with recently developed tri-angular (TRI) baffles, and tri-flower (TF) baffles with conventional segmental (SG) baffles at different flow rates. Simulations have been performed to analyze the heat transfer coefficient, pressure drop, and overall thermo-hydraulic performance among the recently developed TRI-STHX, TF-STHX and conventional SG-STHX. The thermo-hydraulic performance of the numerical model of SG-STHX shows the promising results while validating it with the experimental results, Esso and Kern methods. Then the same study is carried out for comparing the two novel baffles with segmental baffle. The results depict that, novel baffles are much appreciable in increasing heat transfer coefficient. The TF-STHX offers a greater heat transfer coefficient than all others but also offers a higher pressure drop at the same flow rate. Computing the comprehensive performance (hs??p), the TRI-STHX offers a prominent increment in thermo-hydraulic performance compared to others. Moreover by inserting twisted tapes at the tube side, there is noticeable increase in heat transfer coefficient which tends to increase the thermo-hydraulic performance of STHX. By comparing the flow patterns of TRI-STHX and SG-STHX, the novel TRI-STHX shows the reduction in shell-side induced vibrations and hence helped to increase the overall efficiency of the STHX.

The most extensively used heat exchanger in numerous research fields and industrial processes is the shell and tube heat exchanger. The selection of the baffle plays a vital role to regulate and increase the thermohydraulic performance and also to decrease fluid-induced vibrations due to shell side flow. 3-D computational fluid dynamics (CFD) and fluid-structure interaction (FSI) have been done to analyze the pressure drop, heat transfer coefficient, vortex shedding, and tube deformation due to induced vibrations among the recently developed clamping antivibration baffles with square twisted tubes, helical baffles with cylindrical tubes, and conventional segmental baffles with cylindrical tubes at different shell side flow rates by using commercial software ANSYS. Complete heat exchangers are modeled for numerical comparison; the thermohydraulic performance of the numerical model shows the suitable agreement by validating it with already published results and Esso method for single segmental baffles. It is then used to compare the performance of the same heat exchangers with CBSTT and HBCT. Thermohydraulic performance of CBSTT-STHX is better than SGCT-STHX. The heat transfer coefficient of heat exchangers with tube-to-baffle-hole clearance is higher and there is a reduction in the pressure drop compared to the results of STHXs without tube-to-baffle-hole clearance. The deformation in the tubes and vortex-induced vibrations are minimum in STHX with CBSTT than in STHXs with HBCT and SGCT.

No abstract