Heat transfer and nanofluid flow over a porous plate with radiation and slip boundary conditions

Presence of different terms with various values can alter the thermal behavior of the nanofluids flow over porous surfaces.The aim of this research is to study the influence of nanoparticles volume fraction,nanoparticles type,suction or injection,the heat generation or absorption,the Eckert number,thermal and velocity slip parameters,and radiation on the velocity and temperature fields on the flow and heat transfer over a porous flat plate.Four different types of nanoparticles including metal nanoparticles (Cu),metal oxide nanoparticles (Al2O3) and carbon-based nanomaterials (MWCNTs and SWCNTs) which were dispersed in the water (as based fluid) are studied.The governing equations are converted into the ordinary differential equations using similarity solution and solved numerically by the RKF45 algorithm.The results of the simulations showed a contradiction with the results of other researchers who expressed that using nanoparticles with higher thermal conductivity and volume fraction led to increasing heat transfer rate in nanofluids;this study proves that,in some cases,boosting the volume fraction of nanoparticles has a potential to decrease the heat transfer rate due to significant changes in values of some parameters including radiation,heat generation,and viscous dissipation.

Towards the development of integrated monitoring system for retreat mining operations

Through cooperative research between the government,the private sector, mining companies and equipment manufacturers,considerable progress had been made during the last decade in studying the mechanics of strata failure and acquiring the know- ledge needed to develop an integrated monitoring system for assessing local roof stability. Because of higher geotechnical risks in retreat mining operations,it was both important to develop panel layout designs that control convergence and stress and to monitor ground response during operations to verify designs and provide warning of impending stability problems.For detecting both localized roof stability problems and global overburden col- lapse mechanisms,the proposes an integrated panel-wide monitoring system which com- bines the capabilities of load rate monitoring of mobile roof supports (MRSs) with deforma- tion measurements using an extensive array of sensors located near the mining face and throughout the panel.Two monitoring methods for the detection of localized roof stability problems have been evaluated on the basis of mine measurements and numerical model- ing considerations.These are load rate monitoring of the hydraulic cylinders of mobile roof support (MRS) and re mote monitoring of roof movements.Analyses of field data in retreat sections show that roof instabilities are influenced by: (1) pillar failure,(2) pillar yielding,(3) mine seismicity (bumps),(4) geologic structures,and (5) panel layout designs and practice. Pillar yielding and unloading can be conveniently monitored by the load rate monitoring device,but to detect impending localized roof falls,additional ground deformation meas- urements are needed near the mining face.By increasing the number of deformation measurements in the entire panel,additional safeguards can be achieved for detecting overburden collapse mechanisms while continuously monitoring local roof stability close to the retreat line.

Improving shipboard electronics cooling system by optimizing the heat sinks configuration

With the increase of high-power electrical components in modern ships,especially fully electric ships with electric propulsion drive(EPD),the cooling of EPD electrical components has become particularly important.Providing optimal configurations for heat sinks with high thermal efficiency plays an essential role in this regard.A new technique for improving the efficiency of heat sinks is the utilization of perforated fins.This study examined the effects of perforation geometry(shape and size)on laminar airflow flow and heat transfer characteristics over a perforated plate-fin heat sink.Three-dimensional simulations were conducted using the finite-volume scheme based on the SIMPLE algorithm.In this research,the effects of perforation shape and size on various parameters,e.g.,total drag force,average Nusselt number,perforated fin efficiency(PFE),heat transfer performance enhancement(HTPE),and fin optimization factor(η)were evaluated.The results confirmed that at a specific heat transfer surface area for perforated fins,the highest efficiency is achieved by circular perforations.In contrast,the square perforations due to geometric similarity to rectangular fins could reach the maximum size.Consequently,fins with square perforations could achieve the most optimal configuration.Also,results showed that for a constant perforations size,change in perforations shape improves HTPE,PFE,andηby more than 40%,45%,and 110%,respectively.Also,by modifying perforations size for a specified shape,an increment of more than 35%,40%,and 150%is observed in HTPE,PFE,andη,respectively.