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[en] Steam condensation tests were conducted on titanium corrugated tubes at the pressure of 5 kPa and 10 kPa, which are the operating pressures of a power plant condenser. Seven 22.2 mm O.D titanium corrugated tubes had 6.4 mm ≤ p ≤ 22.1 mm and 0.2 mm ≤ e ≤ 0.6 mm. The condensation heat transfer coefficient increased as the corrugation pitch or the corrugation depth decreased. The tube having p = 6.4 mm and e = 0.2 mm yielded the highest heat transfer coefficient with the enhancement from 57 % to 75 %. Comparison with Mehta and Raja Rao correlation revealed that the data are predicted within ±15 %.
[en] In this paper, different heat sinks are investigated to improve CPU cooling experimentally. Different types of copper heat sinks including a novel “porous heat sink” are proposed and compared to obtain the optimum heat transfer rate. Water and Al2O3/water nanofluids (40 nm) in two different volume fractions (0.1 and 0.2 vol.% from 40-nm nanoparticles) are used as heat transfer fluid to cool the CPU. Different flow rates are also examined in the experimental study. The Nusselt number, wall temperature, thermal resistance and LMTD temperature have been analyzed for a wide range of parameters of the heat sinks. Also, the effect of geometry, heat transfer fluid, input power and flow rate on the heat transfer rate is reported. The result shows that the geometry of the heat sink has an important effect on the thermal performance of the system. The rate of heat transfer in the proposed novel porous heat sink is larger than the other cases. The Nusselt number in the porous heat sink by using nanofluids is 2.2 times larger than the heat sink with an inline pattern.
[en] Nanofluid that made up of fluid and solid nanoparticles has gained attention from diverse fields due to its superior thermophysical properties to enhance the performance of different systems which require flowing medium with excellent heat transfer behavior. Many past researchers have proven that conventional heat transfer fluid can be replaced by the rising nanotechnology–nanofluid which showed astonishing performance under different circumstances. In this paper, we attempt to present a recent review on the consequences of implantation of nanofluid, especially in vehicle engine cooling system and other heat transfer applications such as solar collector, electronics cooling system, flow boiling and thermal energy storage system. Thermophysical properties and heat transfer performance of nanofluids obtained in simulation, test rigs and even real vehicle engine experiments are discussed thoroughly. Models and correlations used by past researchers to compute thermophysical properties are also included. In the last part, various advantages from using nanofluid are summarized, and suggestions for research gap between past studies are discussed to further improve the investigation work in the future.
[en] The convective heat transfer coefficient of the mold is an important parameter in the numerical simulation of the injection molding process, and it significantly affects the results. This influences many factors related to processability including the time required for filling and solidification. This study examines the previous work on this coefficient, including commercial implementations, and explains its characteristics. From real cases, the filling time, solidification time, and pressure distribution have been presented according to this coefficient, and a method for treating it is suggested.
[en] Recently, phase-coherent heat transport in superconducting tunnel junctions has received great interest. On the one hand, it allows for the realization of caloritronic circuits. On the other hand, this can serve as a probe of fundamental properties of quantum matter. Here, we investigate heat transport in junctions made from topological superconductors. We demonstrate that the thermal conductance can probe Majorana physics and enables us to distinguish between helical and chiral superconducting pairing.
[en] Radiative–convective flow studies find wide range of applications in furnace design, solar fans, photochemical reactors, turbid water bodies, etc. The present article focusses on unsteady radiative–convective hydromagnetic couple stress fluid (CSF) flow from a vertical cylinder using the thermodynamic concept. The obtained governing equations of the present model are resolved by a well-organised numerical scheme. The unsteady nature of friction, entropy, coefficients of heat and mass transfer (HMT) along with the time-independent state pattern of flow-field profiles, are shown graphically for distinct values of governing radiation parameter, magnetic parameter, concentration parameter, and constant parameter to display important aspects of the solution. To analyse the HMT process in a 2D domain, Bejans flow visualisation is considered along with isotherms, streamlines, and isoconcentration lines. The Bejans HMT flow visualisation shows that the heat and mass function contours are denser in the foremost verge of the hot surface of the cylinder compared to other contours. The result indicates that the entropy generation (EG) parameter increases with decreasing values of radiation and magnetic parameters. Also, the entropy parameter increases for increasing values of concentration parameter or constant parameter. (author)
[en] The word cryostat is made up of a word whose meaning is cold and stable. Mainly it is a container having a device kept at very low temperature and provides thermal insulation to that device. Sir Dewar was the first who has invented it with double-walled design. Cryogenic liquids are filled inside the cryostat. There should be no heat transfer into the cold vessel of the cryostat. In this paper, a process to reduce thermal radiation into the cryostat as well as the minimum required materials to achieve minimum heat load has been discussed. The main function of the cryostat is to provide thermal insulation, mechanical housing of the cryogenic devices and cooling of the device for its safe and reliable operation
[en] We present experimental observations suggesting that non-diffusive avalanche-like transport events are a prevalent and universal process in the electron heat transport of tokamak plasmas. They are observed in the low confinement mode and the weak internal transport barrier plasmas in the absence of magnetohydrodynamic instabilities. In addition, the electron temperature profile corrugation, which indicates the existence of the shear flow layers, is clearly demonstrated as well as their dynamical interaction with the avalanche-like events. The measured width of the profile corrugation is around , implying the mesoscale nature of the structure. (paper)