Alpaslan Turgut

Measurement of thermal conductivity of edible oils using transient hot wire method.

Thermal conductivities of three different edible oils, namely sunflower oil, corn oil and olive oil, were measured at temperatures 25, 40, 60, and 80°C. The measurements were carried out using a hot wire probe method. The calibration of the probe was performed using 0.3% agar gel with water and glycerin. In general, thermal conductivities of oils used in this study are found to be decreasing with temperature. The values of thermal conductivity measured are quite near to each other, the highest and the lowest being respectively 0.168 W/m K for sunflower oil at 25°C and 0.152 W/m K for corn oil at 80°C.

An Investigation on Thermal Conductivity and Viscosity of Water Based Nanofluids

In this study we report a literature review on the research and development work concerning thermal conductivity of nanofluids as well as their viscosity. Different techniques used for the measurement of thermal conductivity of nanofluids are explained, especially the 3ω method which was used in our measurements. The models used to predict the thermal conductivity of nanofluids are presented. Our experimental results on the effective thermal conductivity by using 3ω method and effective viscosity by vibro-viscometer for SiO2-water, TiO2-water and Al2O3-water nanofluids at different particle concentrations and temperatures are presented. Measured results showed that the effective thermal conductivity of nanofluids increase as the concentration of the particles increase but not anomalously as indicated in the some publications and this enhancement is very close to Hamilton-Crosser model, also this increase is independent of the temperature. The effective viscosities of these nanofluids increased by the increasing particle concentration and decrease by the increase in temperature, and cannot be predicted by Einstein model.

Nanofluids for electronics cooling

The goal of this study is to investigate experimentally the thermal performance of an electronics cooling system which is available in the market. Selected system is a water block used for liquid cooling of a central processing unit (CPU) of a computer. A suitable heater (resistance wire) is fabricated for producing heat similar to CPU. System is instrumented with K-type thermocouples for the temperature measurement of certain points. The experiments were carried out first with water and then with water-based Alumina nanofluid. Nanofluid sample was supplied from NanoAmor Inc., with particle concentration of 6.33 volumetric percent and diluted to 1 volumetric percent with water, by using a probe type ultrasound for 2 minutes at 70 W. During the experiments 60 W power applied to the CPU and the ambient temperature was 19 degree Celcius. Our results show that nanofluids, with low volume concentration (1 percent vol.) of Alumina particles decreases the maximum temperature of the system, almost 2.7 degree Celcius, compared to water.

Thermal analysis of thin film transistor liquid crystal display (TFT-LCD) TV panels with single sided LED bars

In this research thermal and fluid fields of a 32-inch commercial thin film transistor liquid crystal display (TFT-LCD) TV panel were investigated numerically and experimentally. The new trend in the production of TFT-LCD, TV panel is to have slimmer screen displays. The original design with 180 LEDs (light emitting diodes) placed at the top and bottom edges of the panels was modified. In the new design, the panels were illuminated using only 72 LEDs placed underside and inside the panels. By this modification an important cost reduction has been achieved alongside having slimmer screen displays. Heat dissipated by these 72 LEDs must be removed in order to assure good image quality and long service life. Hence an appropriate thermal management is indispensable. To analyze temperature distribution at steady state condition a CFD (computational fluid dynamics) computer code “FloEFD” was used. The results obtained from the computational analysis have been validated by using experimental techniques. For this purpose thermocouples were attached on the panel and after the steady state has been reached, temperatures have been recorded in order to compare them to the distribution obtained by “FloEFD”. Furthermore, a thermal camera image of the panel by FLIR Thermacam SC2000 test device was obtained as another validation for temperature distribution.

Thermal analysis and experimental validation on cooling efficiency of thin film transistor liquid crystal display (TFT-LCD) panels

This research explored the thermal analysis and modeling of a 32” thin film transistor liquid crystal display (TFT-LCD) panel, in the purpose of making possible improvements in cooling efficiencies. The illumination of the panel was insured by 180 light emitting diodes (LEDs) located at the top and bottom edges of the panels. These LEDs dissipate high heat flux at low thermal resistance. Hence, in order to insure good image quality in panels and long service life, an adequate thermal management is necessary. For this purpose, a commercially available computational fluid dynamics (CFD) simulation software “FloEFD” was used to predict the temperature distribution. This thermal prediction by computational method was validated by an experimental thermal analysis by attaching 10 thermocouples on the back cover of the panel and measuring the temperatures. Also, thermal camera images of the panel by FLIR Thermacam SC 2000 test device were also analyzed.

Monitoring and Determination of Wind Energy Potential by Web Based Wireless Network

In this paper, we develop a web based interface which performs a wireless communication with ZigBee protocol for monitoring wind energy potential and also gathering custom reports for determination of the interested wind field. A custom printed circuit board layer is designed for interfacing with all the sensors that are in use. Web based interface is a product of responsive design for platform and device independency. This system enables scalable, accessible, reliable, low cost and low power consumption solution for renewable energy systems.

A study on cooling efficiency improvement of thin film transistor Liquid Crystal Display (TFT-LCD) modules

In recent years, LCD (Liquid Crystal Display) TVs are taking the place of CRT (Cathode Ray Tube) TVs very fast by bringing new display technologies into use. LCD module technology is divided into two main groups; the first one is CCFL (Cold Cathode Fluorescent Lamp) display which was the first type used in LCD TV, the other one is the LED (Light Emitting Diode) module which is the newest display technology comes to make slim TV design. There is a thermal challenge making slim TV design. The purpose of this paper is to investigate the thermal analysis and modeling of a 32″ TFT-LCD LED module, The performance of LCD TV is strongly dependant on thermal effects such as temperature and its distribution on LCD displays The illumination of the display was insured by 180 light emitting diodes (LEDs) located at the top and bottom edges of the modules. Hence, in order to insure good image quality in display and long service life, an adequate thermal management is necessary. For this purpose, a commercially available computational fluid dynamics (CFD) simulation software “FloEFD” was used to predict the temperature distribution. This thermal prediction by computational method was validated by an experimental thermal analysis by attaching 10 thermocouples on the back cover of the modules and measuring the temperatures. Also, thermal camera images of the display by FLIR Thermacam SC 2000 test device were also analyzed.

EXPERIMENTAL STUDY ON THERMAL CONDUCTIVITY AND VISCOSITY OF WATER BASED NANOFLUIDS

nanofluids were investigated for various volumefractions of nanoparticles content and at different temperatures. A 3ωtechnique was developed for measuring thermal conductivity of nano-fluids. The theory and the experimental setup of the 3ω measuringsystem is explained; a conductive wire is used as both heater and sen-sor in this system. At first, the system is calibrated using water withknown thermophysical properties. Measured results showed that theeffective thermal conductivity of nanofluids increases as the concen-tration of the particles increases but not anomalously as indicated inthe majority of the literature and this enhancement is very close tothe Hamilton–Crosser model; also this increase is independent of thetemperature. The effective viscosities of these nanofluids increase by

Evaluating the Thermal Conductivity and Viscosity of CuO-Nanolubricants

In the presented work, thermal conductivity of CuO and its viscosity at three different weight concentrations were investigated. A two-steps method was deployed in order to sonicate successfully CuO nanolubricants samples at three different weight concentrations (0.2 wt%, 0.5 wt%, & 1 wt%). The measurements of thermal conductivity were carried out with a lab-made measurement set, which is based on a 3ω method. The obtained enhancements were 1%, 1.7% and 2.8% for 0.2 wt.%, 0.5 wt.%, and 1 wt.%, respectively. Viscosity was also investigated under different temperatures and it was obtained that adding CuO to the mineral oil had a slight effect on its viscosity at lower concentrations. However, the maximum increment at lower temperature for the higher concentration was 13.1%. Based on the enhancement in thermal conductivity and the low increment in viscosity, CuO nanolubricant can be recommended for enhancing the heat transfer characteristic of the refrigeration compressor

Ferrofluid Plug Actuation for Micro Pumping Systems

Ferrofluids are colloidal mixtures which consist of nanosized magnetic particles suspended in a base fluid. The typical magnetic particles could be maghemite, magnetite or cobalt ferrite etc. To keep a ferrofluid suspension in a stable state is possible by an electrical double layer or by adding surfactant. They have many applications on electrical, mechanical and optical systems. Recently, the ability of being manipulated by an external magnetic field made them considerable for microfluidic systems such as micro operations, pumping and mixing. Among them, micro scaled pumping systems have appeared as a critical research area due to its notable potential to be applied on many biological and electronic systems. Moreover, the development of lab on a chip and the micro total analysis systems for biological issues has revealed the necessity of liquid transport for micro quantities. Micropumps with ferrofluid plug actuation mechanisms are considered to have the ability to fulfill this requirement. Therefore, driving the working fluids with ferrofluid plugs in a micro-sized tube or channel has attracted researchers’ interest. In this study, ferrofluid plug actuated micro pumping systems have been reviewed from the available literature based on their design and their maximum generated flow rate.