Impact of Jet Reynolds Number and Feed Channel Geometry on Heat Transfer in a Channel with Inclined Target Surface Cooled by Single Array of Centered Impinging Jets with Outflow in Both Directions
An experimental investigation has been carried out to study the heat transfer characteristics in a channel with heated target plate inclined at an angle cooled by single array of equally spaced centered impinging jets for three different jet Reynolds numbers (Re=9300, 14400 and 18800). Air ejected from an array of orifices impinges on the heated target surface The target plate forms the leading edge of a gas turbine blade cooled by jet impingement technique. The work includes the effect of jet Re and feed channel aspect ratios (H/d = 5, 7, 9 where H=2.5, 3.5, 4.5 cm and d=0.5 cm) on the heat transfer characteristics for a given orifice jet plate configuration with outflow exiting in both directions (with inclined heated target surface). In general, It has been observed that, H/d=9 gives the maximum heat transfer over the entire length of the target surface as compared to all feed channel aspect ratios. H/d=9 gives 3% more heat transfer from the target surface as compared to H/d=5 (for Re=14400). Also, it has been observed that the magnitude of the averaged local Nusselt number increases with an increase in the jet Re for all the feed channel aspect ratios studied.
Enhanced heat transfer characteristics of conjugated air jet impingement on a finned heat sink
Air jet impingement is one of the effective cooling techniques employed in 
 micro-electronic industry. To enhance the heat transfer performance, a 
 cooling system with air jet impingement on a finned heat sink is evaluated 
 via the computational fluid dynamics method. A two-dimensional confined slot 
 air impinging on a finned flat plate is modeled. The numerical model is 
 validated by comparison of the computed Nusselt number distribution on the 
 impingement target with published experimental results. The flow 
 characteristics and heat transfer performance of jet impingement on both of 
 smooth and finned heat sinks are compared. It is observed that jet 
 impingement over finned target plate improves the cooling performance 
 significantly. A dimensionless heat transfer enhancement factor is 
 introduced to quantify the effect of jet flow Reynolds number on the finned 
 surface. The effect of rectangular fin dimensions on impingement heat 
 transfer rate is discussed in order to optimize the cooling system. Also, 
 the computed flow and thermal fields of the air impingement system are 
 examined to explore the physical mechanisms for heat transfer enhancement.
Refinement of crystal structure parameters using convergent‐beam electron diffraction: the low‐temperature phase of SrTiO3
The method to refine crystal structure parameters (atom positions and Debye–Waller factors) using convergent-beam electron diffraction (CBED), which is applicable to crystal structure analysis of a small specimen area down to a few nm in diameter, is studied. The line profiles of higher-order Laue-zone reflections are recorded using imaging plates. Theoretical intensities are calculated based on the dynamical theory of electron diffraction with the aid of the generalized Bethe approximation to shorten calculation time. The structural parameters are determined by fitting the experimental profiles with the theoretical ones using a nonlinear least-squares method. The present method has been applied to the low-temperature phase of SrTiO3. The structural parameter or the rotation angle of the oxygen octahedron has been determined to be \varphi = 1.12 (4)°, which shows good agreement with that obtained from electron spin resonance experiments.