Yahya Sheikhnejad

Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration (IZM) · wafer level

In this study, the thermal performance of a 2-D turbulent natural convection airflow inside a solar air heater is improved by using a flexible porous vortex generator, which is a self-sustained passive oscillator. The inclined thin elastic porous winglet, used as vortex generator, is attached on the heated wall for flow mixing and convection enhanc...

An investigation of 2D laminar magnetohydrodynamics couple stress hybrid nanofluid is performed with inclined magnetic field over the stretching/-shrinking surface embedded in porous media. The quiescent water-based nanofluid is subjected to the external force by pulling the two ends of the sheet with equal magnitude and opposite forces. The govern...

A steady-state, two-dimensional flow of Rivlin-Ericksen magnetohydrodynamics (MHD) fluid flow induced by stretching of the sheet of porous medium considering heat and mass transfer is investigated in the present analysis. The fluid flow is influenced by a uniform magnetic field. The inverse Darcy model, as well as thermohydrodynamic characteristics...

The present work is focused on the slip flow of an electrically conductive viscoelastic fluid over a porous stretching/shrinking surface with mass transpiration and radiation. The closed-form analytical solutions for non-dimensional highly nonlinear governing equations consist of conservation of momentum, species, and energy are derived in the form...

Limited reserves of fossil fuels, rising environmental concerns, and a remarkable increase in electricity demand have led to the necessity of harnessing solar energy on a large scale. For this purpose, there has been a noticeable stimulation into photovoltaic power plants (PVPPs) over the last three decades, but the land requirement for PVPPs is st...

Pathogen droplets released from respiratory events are the primary means of dispersion and transmission of the recent pandemic of COVID-19. Computational fluid dynamics (CFD) has been widely employed as a fast, reliable, and inexpensive technique to support decision-making and envisage mitigatory protocols. Nonetheless, the airborne pathogen drople...

This special issue aimed to contribute to the novelties and frontiers in porous media with a special focus on analytical models and their comparison with numerical and experimental approaches. The published papers included within this special issue help engineers and programmers to keep the models of real apparatus as simple and accurate as possibl...

This special issue presents up-to-date studies on porous media with a special focus on analytical models and their capability in reconstructing numerical and experimental results. The published papers included within this special issue provide analytical and semi-analytical models for a wide range of problems including micro-polar liquid flow induc...

Airborne pathogen respiratory droplets are the primary route of COVID19 transmission, which are released from infected people. The strength and amplitude of a release mechanism strongly depend on the source mode, including respiration, speech, sneeze, and cough. This study aims to develop a simplified model for evaluation of spreading range (length...

COVID19 pathogens are primarily transmitted via airborne respiratory droplets expelled from infected bio-sources. However, there is a lack of simplified accurate source models that can represent the airborne release to be utilized in the safe-social distancing measures and ventilation design of buildings. Although computational fluid dynamics (CFD)...

In this study, the important role of radiating gas effect to obtain higher thermal performance in a planar double-pass solar gas heater (DP-SGH) is discussed. Two inclined passages are deployed in series format but in a side-by-side configuration. The exploitation of radiating gas, with higher radiative characteristics respect to the usual working-...

Airborne pathogen respiratory droplets are the primary route of COVID19 transmission, which are released from infected people. The strength and amplitude of a release mechanism strongly depend on the source mode, including respiration, speech, sneeze, and cough. This study aims to develop a simplified model for evaluation of spreading range (length...

The outbreak of COVID-19 necessitates developing reliable tools to derive safety measures, including safe social distance and minimum exposure time under different circumstances. Transient Eulerian-Lagrangian computational fluid dynamics (CFD) models have emerged as a viably fast and economical option. Nonetheless, these CFD models resolve the inst...

According to the global consensus on mitigation of greenhouse gas and human footprint as well as improvement of industrial sustainability by the exploitation of renewable energy, the mission of this study dedicated to the performance enhancement of planar solar chimneys in converting much more solar radiation into air enthalpy by vortex generation...

This study steps into the roadmap of agenda 2030 to mitigate the human footprint on an environment with the aim of management of energy consumption in residential/commercial buildings. In order to materialize this concept, a new generation of adaptable systems of intelligent supervisory predictive control (ISPC) is introduced and implemented in whi...

A countless amount of energy has been wasted in all kinds of expansion valves (EV) in industries. In fact, EVs, including regulators, throttling valves, capillary tubes, etc., have been used to intentionally reduce the potential of carrier fluid. City gate stations (CGS) have been recognized as one of the important points with high potential for en...

Urban and rural areas are the cradles of human development and civilization as all practical progress and feasible products have emerged from these places. Having a clear understanding of the sustainability of these areas, especially the progress of research in this field, is highly important. This study undertakes a comprehensive scientometric ana...

In this study, a new application of a Tesla turbine (TT) is presented in which a TT is introduced as a promising solution to enhance the energy efficiency of refrigeration cycles. For this special purpose, a TT is represented as a regenerative system that minimizes the wasted energy without compromising the system output quality or sacrificing stan...

This study addresses a new generation of adaptable intelligent control systems for energy management. The proposed approach consists of a high-level predictive control system based on advanced simulation and optimization algorithms which interact with conventional machine-level controllers of HVAC systems, e.g., PID, in order to define optimized se...

In this experimental-numerical study, effects of transverse magnetic field of parallel magnet bars perpendicular to the fluid flow direction and partially filled porous media are investigated. Moreover, constant heat flux is applied on the outer surface of a circular straight horizontal pipe and concentric porous media is embedded inside it. Magnet...

This study is dedicated to the thermal analysis and thermo-hydrodynamic simulation of an air-to-air plate heat exchanger in order to solve its routine problem in industry. The compact type of cross-flow plate heat exchanger, in which corrugated plates pile up tightly and delicately brazed to each other, has been used in many situations and has many...

This study is dedicated to the thermal analysis and thermo-hydrodynamic simulation of an air-to-air plate heat exchanger in order to solve its routine problem in industry. The compact type of cross-flow plate heat exchanger, in which corrugated plates pile up tightly and delicately brazed to each other, has been used in many situations and has many...

We present a characterization of power penalty using p-i-n (PIN) and avalanche photodiode (APD) receivers for different extinction ratios (ER) of the transmitted signal. A simple approach based on experimental fitting is presented to describe the power penalty. The model is in a good agreement with the experiment, predicting both PIN and APD result...

This study include experimental and three dimensional numerical analysis of conjugate steady state laminar forced ferroconvection of Newtonian incompressible ferrofluid through horizontal circular pipe under constant heat flux and in presence of transverse magnetic field. Magnetic field was applied by two fixed parallel magnet bars at the beginning...

In any wavelength sensitive application, extensive care should be taken in addressing the wavelength drift issues. In the case that laser tuning is conducted by using thermoelectric cooler, an accurate expression is needed to describe transient characteristics of Peltier device to achieve maximum controllability. In addition, thermal tuning issues...

In this study, steady state laminar ferroconvection through circular horizontal tube partially filled with porous media under constant heat flux is experimentally investigated. Transverse magnetic fields were applied on ferrofluid flow by two fixed parallel magnet bar positioned on a certain distance from beginning of the test section. The results...

ferrofluid as a lubricant was used in journal bearing and magnetic field of wire of carrying current was applied to the system

In this study forced convection of ferrofluid steady state laminar flow through circular axisymmetric horizontal pipe under different magnetic field is investigated. Linear, square root and parabolic profiles are three considered magnetic field distributions. Pipe is under constant heat flux and linear axial magnetic fields with the same magnetic e...

The effect of magnetic field on laminar forced convection of ferrofluid in a horizontal tube partially filled with porous media is investigated. Governing equations are solved numerically using finite volume method and Simple algorithm, to obtain thermohydrodynamic characteristics and enhancement of heat transfer for different porous locations and...

The effect of magnetic field on laminar forced convection of ferrofluid in a horizontal tube partially filled with porous media is investigated. Governing equations are solved numerically using the finite volume method and the SIMPLE algorithm, to obtain thermohydrodynamic characteristics and enhancement of heat transfer for different porous locati...

In this study numerical simulation of thermohydrodynamic characteristics of mud flow and mortality threshold of PDC bits are investigated using computational fluid dynamic technics. Governing equations of fluid flow were discretized by FVM and solved by SIMPLE algorithm. Well wall temperature increased linearly and block-off method is used to model...

In this study analytical solution of conduction heat transfer in long circular wire of carrying current is investigated. When wire of carrying current is used in miniaturized electronic devices, heat recovery from wire plays a major role on amount of waste of energy and indeed needs to be estimated precisely specially in expensive environment where...