Spray technology has numerous applications in general and cooling microchannels in particular. But before that study of the controlling parameters on which spray performance depends need to be explored. Present work describes an experimental study on microchannel cooling with jet and spray at different pressure combinations of air and water. The experimental facility was developed at the School of Mechanical Engineering, KIIT, deemed to be University, Bhubaneswar, to investigate the effect of various controlling parameters like fluid pressure, flow rate, nozzle to surface distance and heat input on jet and spray cooling of microchannels. The input parameters like air pressure and water pressure along with nozzle to surface distance were optimized. The input parametrs such as air and water pressure in the range of 1 bar to 3 bar, nozzle tip to surface distance in the range of 10 to 20 mm were considered during the tests. As a result, at 1 bar air pressure, 3 bar water pressure and 17.42 mm nozzle tip to surface distance, the maximum heat transfer coefficient was achieved as predicted optimal solution through response surface methodology (RSM). The data were compared with that of the earlier researcher's experimental work. The experimental results revealed that the employment of spray impingement cooling technique on microchannels provided significant improvement in removal of heat flux with less consumption of coolant.

Purpose The purpose of this study is to investigate dimensional accuracy (Δd), surface roughness (Ra) and micro hardness (HV) of partial dentures (PD) prepared with synergic combination of fused deposition modelling (FDM) assisted chemical vapour smoothing (CVS) patterns and conventional dental casting (DC) from multi-factor optimization view point. Design/methodology/approach The master pattern for PD was prepared with acrylonitrile butadiene styrene (ABS) thermoplastic on FDM set-up (one of the low cost additive manufacturing process) followed by CVS process. The final PD as functional prototypes was casted with nickel–chromium-based (Ni-Cr) alloy by varying Ni% (Z). The other input parameters were powder to water ratio P/W (X) and pH value (Y) of water used. Findings The results of this study suggest that for controlling the Δd and Ra of the PD, most important factor is X, followed by Z. For hardness of PD, the most important factor is Z. But from overall optimization viewpoint, the best settings are X-100/12, Y-10 and Z-61% (in Ni-Cr alloy). Further, based upon X-bar chart (for HV), the FDM-assisted DC process used for preparation of PD is statistically controlled. Originality/value This study highlights that PD prepared with X-100/12, Y-10 and Z-61% gives overall better results from multi-factor optimization view point. Finally, X-bar chart has been plotted to understand the statistical nature of the synergic combination of FDM, CVS and DC.

Abstract-The need for a better cooling purpose in bio medical, electronics, microprocessors and radars has attracted many researchers. Since, microchannels fulfil this objective it's machining through different micro machining techniques requires more skill and knowledge. Micro electrical discharge machining (EDM)is considered as one of the advanced methods of machining micro tools, dies, channels, grooves etc. More emphasis should be given to this machining process so that complicated geometries with least effort can be produced. In the present work critical study has been done on different tool materials as well as workpiece materials used on machining work table in micro EDM with different new strategies of machining will be helpful to enhance understanding of the subject. Along with this a direct method of getting tools for making micro holes and grooves on workpiece is suggested.

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