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Micromixers are being extensively used in micro total analysis systems (µTAS) and chemical processing. Passive micromixers are most preferable due to their robustness, ease of integration and low cost. However, it is difficult to achieve rapid mixing in passive mixers. Previous studies on passive T-mixer showed that convective effects at high Reynolds number improve mixing significantly. In the present study, a swirl component of velocity is imparted at inlets of T-mixer to enhance the convective effects. Numerical results have shown that the reverse orientation of the swirl (R-O-Swirl) in inlet channels favored earlier onset of engulfment regime which enhanced mixing at lower Reynolds number (66 < Re < 180). At high Reynolds number (Re > 266), swirl with same orientation (S-O-Swirl) in inlet channels increased the swapping of samples at junction which significantly improved mixing. Nearly three hundred to five hundred percent increase in mixing index is obtained with R-O-Swirl at 160 < Re < 180 and thirty to seventy percent increment with S-O-Swirl at 266 < Re < 372 as compared to T-mixer without swirl. Therefore, it is noted that the presence of swirl component at inlets can further enhance the engulfment regime and improve mixing efficiency of T-micromixer. [ABSTRACT FROM AUTHOR]

LED light must be cooled to avoid reaching a certain temperature. Two different 3D practical domains of LED light are modelled, (i) square aluminium plate with a cylindrical plate and an LED module (model I), (ii) the same provision of model I with 25 fins (model II). ANSYS 16.0 is used for solving the problem. Temperature distribution, junction temperature (Tj ) and heat flux are estimated. Analyses are carried out for various ambient temperatures (Ta) and for different LED power dissipations (Q) to identify the safe operating conditions. In model I, it is found that 38% of working conditions go beyond the critical limit of Tj and it is reduced to 21.4% in model II. In model II, for low Ta of 30 and 40°C with all Q considered in this analysis are safer. If Ta is between 30 and 80°C, then Q must be maintained at 0.5 to 1.25 W. Beyond this, conditions are not safe. [ABSTRACT FROM AUTHOR]

Freeze drying is a highly advanced dehydration technique used for preserving pharmaceuticals, human organs transplanted to others and highly heat sensitive food products. During the freeze drying, there are two layers formed namely dried region and frozen region. In this present work, a numerical model is developed to estimate the temperature distribution of both regions. The sample object considered is skimmed milk. The transient heat conduction equations are solved for both regions of dried and frozen region. The interface layer between the two region is considered as moving sublimation front as same as the realistic case. Radiative boundary condition at the top and convective boundary condition at the bottom are considered. The model has been solved by finite difference method and the scheme used is backward difference in time and central difference in space (implicit scheme), which generates set of finite difference equations forming a Tri-Diagonal Matrix. A computer program is developed in MATLAB to solve the tri-diagonal matrix. The temperature distribution along the length of the product with varying chamber pressures and the sublimation front temperature with time are estimated. The transient effect of sublimation front movement was estimated with different applied chamber pressure. It was noticed that at lower pressure the sublimation rate is very fast. [ABSTRACT FROM AUTHOR]