Axial fans are one of the major power consuming cooling systems in most of the devices being used in daily basis. So, it is very important to predict the aerodynamic performance of the fan design. One way of estimating the fan performance in full 3D scale is by using Computational fluid dynamics. Turbulence models plays an important role in application of CFD for Axial flow fans. It is important to choose proper turbulence model in order to get the most accurate results. In this study, a baseline model experiment was chosen and validated. Both steady and transient studies have been carried out. Steady state simulation was performed using Reynolds Averaged Navier Stokes turbulence models such as Spalart Allmaras, RNG k-ε with swirl dominant flow, k-ω SST model and Transition SST model. Transient simulation is performed using RANS model such as Spalart Allmaras, Standard k-ε with standard wall function, RNG k-ε with swirl dominant flow, k-ω SST model, Detached Eddy Solver and Standard k-ω with embedded Large Eddy Solver. Both studies reveal that with coarse mesh URANS model can predict more accurate than Hybrid URANS models. Out of all the models DES showed a very good prediction in terms of pressure drop.

No abstract

Stirling regenerator is one of the emerging heat exchanger systems in the area of cryogenic cooling. Many kinds of research have been conducted to study the efficiency of Stirling regenerators. Therefore, the principles and related knowledge of Stirling refrigerators must be thoroughly understood to design a regenerator with excellent performance for low-temperature and cryogenic engineering applications. In this study, an experimental setup is developed to estimate the pressure drop of the oscillating flow through two different wire-mesh regenerators, namely, 200 mesh and 300 mesh, for various operating frequencies ranging from 3 (200 RPM) to 10 Hz (600 RPM). Transient, axisymmetric, incompressible, and laminar flow governing equations are solved numerically, and source terms are added in the governing equations with the help of the porous media model and the Ergun semiempirical correlation, assuming that the wire meshes are cylindrical particles arranged uniformly. Simulation results show that the numerical predictions of temporal pressure variation are in reasonably good agreement with those of experimental findings. It is also found that the Ergun correlation works more accurately for higher flow rate conditions.

Heat exchangers are one of the most heavily studied devices and extensive work has been performed over the years to increase their effectiveness. The present work investigates the heat transfer characteristics of an APHE (annular porous heat exchanger) in terms of different parameters. A modified design for the APHE is proposed, which resembles a conventional double pipe heat exchanger, with the annular portion of the outer pipe filled with a specific type of porous medium in order to intensify the heat transfer process. Commercial CFD package ANSYS Fluent has been utilized to investigate the performance of the proposed design numerically. Introduction of porous medium induces an increase in pressure loss which is undesirable; hence, a trade-off is present between hydrodynamic and thermodynamic performance. In the present work different inlet parameters have been modified such as different values of porosity (70% to 90%), different inlet velocities of hot fluid (1 m/s to 9 m/s), different inlet velocities of cold fluid (5 mm/s to 25 mm/s), and different inlet temperature of hot fluid (400 K to 480K), and their effects on the outlet parameters have been studied. The change in heat transfer has been presented quantitatively along with other significant parameters such as mass flow rate, pressure drop and hot gas outlet temperature. These results have been compared with the values for conventional heat exchangers in order to establish the effectiveness of APHE.

Axial fans are found to be one of the major sources of the noise in modern devices such as PCs, HVAC systems, turbo engines and etc. Lot of researches were going on for decades to reduce this unwanted noise. Researchers have found that application of leading-edge serrations will lead to reduction of noise from the bio-inspired study on the wings of barn-owl. This project involves in the study of effect of Aerodynamic performance of axial fan in terms of pressure drop and aerodynamic efficiency using commercial CFD tool ANSYS FLUENT. Analysis have been carried out for a base model without serration and same model with serrations for various flow rates. The results are validated with the experimental results obtained by Krömer et al [1] and found to be in reasonably good agreement.