The present article focuses on the evaluation of a first-moment closure model applicable to film cooling flow and heat transfer computations. The present first-moment closure model consists of a higher level of turbulent heat flux modeling in which two additional transport equations for temperature variance kθ and its dissipation rate εθ are ...

Forced convection boiling in microchannels is studied experimentally under the uniform heat flux boundary condition. Several microchannel heat sinks with integrated temperature sensors, spanning two orders of magnitude in height 5–500 μm, have been fabricated with designed nucleation sites on the bottom surfaces. The microchannels are capped by a glass wafer to monitor bubble activity using vid...

In this paper, convection heat transfer of Al2O3-water nanofluid turbulent flow through internally ribbed tubes with different rib shapes (rectangular, trapezoidal and semi-circular) is numerically investigated. For each rib shape, the optimum geometric ratio and volume fraction were calculated using entropy generation minimization technique. The governing equations in...

the vehicle braking system is considered to be one of the most fundamental safety-critical systems in modern vehicles, as its main purpose is to stop or decelerate the vehicle. the frictional heat generated during braking application can cause numerous negative effects on the brake assembly, such as brake fade, premature wear, thermal cracks and disc thickness variation. in the past, surface ro...

The aim of this paper is to enhance thermal performance of a microchannel heat sink by using nanoencapsulated phase change material (NEPCM) slurry as a cooling fluid instead of pure fluid. A threedimensional model of a circular channel using water slurry of NEPCM was developed. The results show a significant reduction in the mean fluid temperature along the channel and heat sink wall temperatu...

Suppose an electric current I flows along a magnetic flux tube that has poloidal flux c and radius a5a(z), where z is the axial position along the flux tube. This current creates a toroidal magnetic field Bf . It is shown that, in such a case, nonlinear, nonconservative J3B forces accelerate plasma axially from regions of small a to regions of large a and that this acceleration is proportional ...

This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the...

In the design of heat exchangers, it is necessary to determine the heat transfer rate between hot and cold fluids in order to calculate the overall heat transfer coefficient and the heat exchanger efficiency. Heat transfer rate can be determined by inverse methods. In this study, the unknown space-time dependent heat flux imposed on the wall of a heat exchanger internal tube is estimated by app...

We have theoretically demonstrated that phonon heat flux can be significantly suppressed in Si and Si/SiO2 nanowires with the periodically modulated cross-section area—referred to as the cross-section-modulated nanowires—in comparison with the generic uniform cross-section nanowires. The phonon energy spectra were obtained using the five-parameter Born–von Karman-type model and the face-centere...