نشریه علوم کاربردی و محاسباتی در مکانیک
سال سی و چهارم شماره 4 (زمستان 1401)

This paper investigates the free vibrations of a sandwich panel with metal/composite hybrid face sheets reinforced with carbon and glass fibers and a soft core with simply-support boundary conditions. To derive the governing equations, with third shear deformation theory (TSDT) of multilayers and Hamilton's principle have been used for a rectangular sandwich panel with a metal/composite hybrid top and bottom face sheets. It is assumed full connection of the face sheets to the softcore and linear displacement. After comparing the results of the present research with similar and ensuring the correctness of the extracted equations, the parameters effective, volume fraction metal layer and composite with angular layering, the ratio of length to thickness and thickness of the core to the face sheet, length sandwich panel to width and the layup (0,90) and (45, -45) for two types of glass and carbon fibers hybridized with AL 2024 T3 aluminium investigated. The results showed that the carbon/aluminium hybrid with the volume of the composite (Vc) equal to 0.5 has the highest natural frequency value in the first five mode shapes with layup AL/-45/45/core/45/-45/AL. Also, by increasing the thickness of the softcore to the surface and the ratio of length sandwich panel to total thickness, the effect of the aluminium layer decreases.

In the present research, an integrated solar-geothermal energy system is proposed. This energy system consists of a single flash geothermal cycle, single effect absorption refrigeration cycle, heat pump cycle for drying process, solar energy saving comportment, two steam turbines for power production, cooling system for domestic usage and heating for industrial application. The aim of this system is providing cooling and heating for domestic and industrial appliances and drying food products. The energy and exergy efficiency of the system were 92% and 57%, respectively. The effect of parameters such as surrounding temperature, the temperature and the mass flow rate of geothermal tank, and the outlet water temperature of the generator of absorbtion cooling system on energy and exergy efficiency of the system were investigated. The overall energy efficiency does not change by increasing surrounding temperature from 270 K to 320 K, but overall exergy efficiency, turbine 1, and turbine 2 decrease almost 7%, 3% and 4%, respectively.

In this research, the role of Phase Change Materials (PCM) in energy saving in lightweight prefabricated buildings is studied. For this purpose, a typical building in Kermanshah, Iran is simulated in DesignBuilder software. A split unit is used as air conditioning system. The annual energy consumption of the building in the reference state is 2577.27 kWh. The implementation of the InfiniteRPCM21C was investigated in all directions including each individual wall, ceiling, four walls simultaneously and the entire building envelope. The southern wall is the best option among the walls with 12.14% energy saving. From an economic point of view, this wall has the best performance as well by saving 2.08 kWh/kgPCM. Implementation on the entire envelope increases savings up to 37.2%. Although this is not an economical case, but it reduces the need for energy to almost zero in four months of the year. By examining the PCM in different layers of the wall, it was found that in all directions, the inner surface of the wall leads to the greatest energy savings. Also, taking account the PCM thickness in the range of 5 to 25 mm showed that the smaller the thickness, the greater the savings per unit mass of the PCM. Therefore, thicknesses more than 20 mm are not recommended. Finally, the effect of the PCM melting point in the range of 18 to 29 degrees Celsius was investigated and it was found that the maximum energy saving is obtained at the melting point of 21 degrees Celsius.

Micro-scale equipment has many advantages such as high thermal efficiency, high heat transfer surface-to-volume ratio, small size, lightweight, low required fluid, and high design flexibility. In the current study, the fluid flow inside the microchannel is modeled by assuming laminar, incompressible, and two-dimensional flow. The slip boundary condition is applied on the walls and the outlet of the channel is considered as fully developed. The effect of various parameters such as dimensionless slip coefficient, Reynolds number, and volume fraction of nanofluid is examined. The obtained results demonstrate that the velocity for the slip coefficient between 0 and 0.04 is higher than that for the slip coefficient between 0.04 and 0.08. Also, as the Reynolds number increases, the place where thermal development is supposed to occur moves towards the center of the channel and towards the outlet of the channel. At a Reynolds number of 10, the temperature of the fluid is enhanced rapidly due to its low velocity, and the slip coefficient does not have a large effect on the velocity profile. At high Reynolds numbers, the temperature profile has a greater effect on the slip velocity coefficient. According to the results, the amount of heat transfer is increased with the volume fraction of the nanofluid.

In this paper, the dynamic stability of a moderately thick rectangular plate floating on stationary fluid under the periodic passage of oscillating rigid bodies is studied. Each of the two ends of a rigid body is connected to a wheel through a suspension system. The fluid loading effect on the plate is modelled using the method of added mass. Using the assumed-mode method, the governing equations are derived based on the Mindlin plate theory. The Floquet theory is employed as a numerical method to obtain stable and unstable zones of the parameters plane. Considering the point moving object model, the effect of moving object modelling on the stability analysis results is also investigated. The results indicate that contact of the plate with the fluid, the plate boundary conditions, the plate’s thickness, the stiffness and damping of the suspension system, the mass ratio of the wheels to the whole rigid body, the rigid body’s length and the moving object modelling method are very effective in domains stability and instability of the system.

One of the most important parameters in the analysis of the vibration behavior of the fuel rod is the elastic properties of spacer grids. In this research the combination of laboratory tests and theoretical formula was used to determine the elastic coefficients of these spacers that is related to fuel assembly with circular design. In order to validate the numerical model a spatial modal test set-up has been designed, constructed and set up to perform the modal test. The modal test results indicate that equivalent density of the dummy fuel rod depends on the natural mode of the rod. Then, the spring coefficients of the middle spacers and end constraints have been modified by comparing the results of numerical simulation with the results of modal tests defined in different supporting states of the hollow rod. The simulation results show that in addition to the middle spacers, also the end constraints have a significant effect on the natural frequencies of the rod. The Sensitivity Analysis results show that these coefficients depend on the natural mode of the rod. In addition, the results show that by updating the spring coefficients of the middle spacers and end constraints the estimation error of natural frequencies has been significantly reduced and the estimation of natural mode shapes based on the modal assurance criterion has been significantly improved.