An introduction to heat transfer

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A User’s Guide

Solar Engineering Of Thermal Processes

A review of the applications of nanofluids in solar energy

The limitation of hot spot cooling in microchips represents an important hurdle for the electronics industry to overcome with coolers yet to exceed the efficiencies required. Nanotechnology-enabled heat sinks that can be magnetophoretically formed onto the hot spots within a microfluidic environment are presented. CrO2 nanoparticles, which are dynamically chained and docked onto the hot spots, establish tuneable high-aspect-ratio nanofins for the heat exchange between these hot spots and the liquid coolant. These nanofins can also be grown and released on demand, absorbing and releasing the heat from the hot spots into the microfluidic system. It is shown that both high aspect ratio and flexibility of the fins have a dramatic effect on increasing the heat sinking efficiency. The system has the potential to offer a practical cooling solution for future electronics.

Dynamic nanofin heat sinks

Template-assisted electrochemical deposition is a straight forward approach for the synthesis of 1D nanostructures (e.g., nanowire, nanorod, and nanobelt) with controllable morphology. This approach is suitable for mass production as it works at ambient pressure and temperature with the properties of synthesized 1D nanostructures being influenced by synthesis conditions during the electrochemical deposition process. This work aims to investigate the influence of stabilizing agent concentration and heating temperature towards the physical behavior of Nickel (Ni) nanowires synthesized via a template-assisted electrochemical deposition approach. In this research, the electrolyte bath was prepared in three different concentrations of the stabilizing agent (6 g/L, 40 g/L and 70 g/L), and the deposition bath temperature used was 30°C, 70°C, and 110°C respectively. The elemental composition was determined using Energy Dispersive X-ray (EDX) analysis to investigate the percentage of pure Ni element in the synthesized nanowires. The diameter, surface texture, and growth length of the synthesized Ni nanowires were characterized using Field Emission Scanning Electron Microscope (FESEM). X-ray diffractions (XRD) was used for crystal size and crystal orientation analysis. Additionally, the mechanical properties of Ni nanowires were extracted via molecular dynamic simulation. Growth length of Ni nanowires found to be significantly improved as the heating temperature increased, but it decreased when stabilizer agent concentration is high. The diffraction patterns for all synthesis conditions exhibited the synthesis Ni nanowires are polycrystalline as the crystalline planes with Miller indices of 111, 200, and 220. All the investigated nanowires showed ductile failure behavior, a typical behavior at larger length scales of Ni.

/pdf/template-synthesis-of-ni-nanowires-characterization-and-sp2x24lehy.pdf

Template synthesis of Ni nanowires: Characterization and modelling

In the present study, mixed convection in a horizontal rectangular duct using Al2O3 is numerically investigated. The effects of different Rayleigh number, Reynolds number and radiation on flow and heat transfer characteristics were studied in detail. This study covers Rayleigh number in the range of 2 106 ≤ Ra ≤ 2 107 and Reynolds number in the range of 100 ≤ Re ≤ 1100. Results reveal that the Nusselt number increases as Reynolds and Rayleigh numbers increase. It was also found that the dimensionless temperature distribution increases as Rayleigh number increases.

Numerical Study of Mixed Convection through Horizontal Duct Utilizing Al2O3

This paper presents an experimental method for evaluating the effusivity values of different scratched temperature sensors. These sensors have a response time on the order of microseconds (50 µs) with a rise time less than (0.3 µs). Two types of scratch were used, mainly abrasive papers with different grit sizes and scalpel blades with different thicknesses to form the sensor junction. The effect of scratch technique on the sensor's effusivity is also investigated. The sensors were tested and calibrated in the test section of a shock tube facility at different operating conditions. It was observed that the effusivity of a particular sensor depends on the Mach number, scratch technique, junction location as well as on the enthalpy condition. It was also noticed that sensor scratched using scalpel blade technique does not require an individual calibration. However, for sensor scratched using abrasive paper technique, a calibration for each sensor is likely to be required. The present results have provided useful and practical data of the effusivity values for different scratched temperature sensors. These data are beneficial to the experimentalists in the field and it can be used for accurate transient heat transfer rate measurements.

An experimental method for effusivity determination of different scratched temperature sensors

Parabolic Trough Solar Collectors

This study is used to compute the primitive variables of moderate supersonic flow based on finite difference computational fluid dynamic methods. The problem considered deals with a three-dimensional external, inviscid ,compressible supersonic flow over a three-dimensional arc circular bump. In this work, Euler equation was solved using time-marching Mac Cormack’s explicit technique. The flow conditions are taken at sea level and Mach number at 1.97. To deal with complex shape of arc circular bump the so-called “body fitted coordinate system” were considered and the algebraic methods were used to generate grids over an arc circular bump. The results showed a good agreement with other published results.

http://textroad.com/pdf/JBASR/J.%20Basic.%20Appl.%20Sci.%20Res.,%203(7)656-666,%202013.pdf

Hussein A. Mohammed

Papers

Template synthesis of Ni nanowires: Characterization and modelling

Numerical Study of Mixed Convection through Horizontal Duct Utilizing Al2O3

An experimental method for effusivity determination of different scratched temperature sensors

Parabolic Trough Solar Collectors

Numerical simulation of three-dimensional supersonic flow around an aerodynamic bump