Couple stresses because of magnetic particles additives on the lubrication performance of a journal bearing system was embraced and scrutinized in the current examinations theoretically. The governing equations of Reynolds (pressure field), energy (temperature field), and heat conduction (temperature field through the solids) are coupled and solved instantaneously in term of temperature and viscosity. After these set of equation pressure is obtained, it is used to obtain the bearing characteristic. It was found that the load currying capacity and maximum pressure are increased due the employing of magnetic fluids along with the couple stresses, as well as side leakage flow and the friction coefficient are decreased. It can be also concluded that the magnetic fluids with couple stresses are better lubricant than magnetic fluid only (l _ = 0), Newtonian fluids, and couple stress fluid ( = 0).
The present study considered an impingement jet using hybrid nanofluid CuO–Cu/water. A single rounded nozzle was used to impinge a turbulent coolant (water) on the hot circular plate at Reynold’s number range of (5,000–15,000). CuO–Cu nanoparticles were physically synthesized at 50 nm size and dispersed by one-step preparation method. The experimentations were conducted with nanoparticle concentrations range of (0.2–1%) by volume. The results showed that the presence of hybrid nanoparticles exhibits a significant improvement in the overall thermal performance of the working fluid. Where the gained heat interpreted by the Nusselt number was found to be 2.8% (in comparing with deionized water) at ϕ = 1% and Re = 15,000, while the minimum gain in the heat was found to be 0.93% at ϕ = 0.2% and Re = 5,000. Furthermore, it was noted that the excessive increase in CuO–Cu nanoparticle concentration causes more pumping power consumption. Moreover, the CuO–Cu nanoparticles residual layer was found to be formed at a high CuO–Cu concentration, which acts as an insulation layer that hinders the heat exchange. It was also found that the threshold of nozzle-to-plate spacing is H = 4, before which, the heat gain is positive, and negative plummet after.
Solar energy is one of the most efficient forms of renewable energy. Solar air collectors are promising utilization of solar energy. The present study used unsteady three-dimensional Computational Fluid Dynamic (CFD) analysis to investigate the heat transfer and fluid friction in solar air collectors with smooth and v-corrugation absorber plates. The studied parameters are Reynolds number, v-corrugation height, and pitch. Three Reynolds number (500, 1000, 1500) values were used with three arrangements configuration of the v-corrugation of relative heights of 0.10, 0.16, and 0.23. Roughness pitches varied between 1.33, 1.66, and 2. By comparing the simulated thermal efficiency with the currently known experimental values, great agreement can be approved. Results show the superiority of the performance of v-corrugated collector against the traditional or smooth type. The outlet temperature obtained in case of relative roughness height = 0.23 and relative roughness pitch = 2 is 61 °C, while it is 53 °C for a smooth type. Also, a higher thermal efficiency of 46.7 % can be obtained compared to 33.01% for smooth type.
An experimental test rig is constructed and designed according to the results obtained from a thermodynamics model solves by EES software assuming a constant generator, condenser, absorber, and evaporator temperatures to study a bubble pump’s performance solar absorption cooling system. The whole system consists of a parabolic trough solar collector, a generator, a condenser, an absorber, an evaporator, and a cooling water system. The used PTC area is designed according to the quantity of thermal energy required to operate the bubble pump cooling system and the minimum solar radiation incident at Kufa city (Najaf/Iraq), which lies on (32°N and 44°E). A modification is added to the collector receiver to ensure water exposure to solar energy for a longer time. The weather features that affected system performance like the solar radiation incident and the ambient temperature are measured for each test. The maximum recorded receiver temperature is 122 °C without water flow, and it is reached to 90.5°C as a maximum in case of water flow through the receiver. The water in the storage tank is reached to 89 C as a maximum. The collector thermal efficiency reaches its maximum value of 69.2 % for a water flow rate of 0.3315 kg/s, while the maximum efficiency at 0.189 kg/s is 68.3%. The maximum recorded generator temperature is 87°C, and at the same test, a minimum evaporator temperature of 17°C is obtained at an ambient temperature of 46.8 °C.
Two-phase flow pattern, pressure drop, and void fraction in vertical transparent pipe of x m internal diameter and y m length is investigated experimentally. The rig is designed to achieve the measurements of pressure drop and void fraction for different combinations of phase superficial velocities such that the regimes encountered are bubbly, slug and annular, which required a wide range of water and air superficial velocities.
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