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Thermal management of electronic components is becoming popular due to the extensive applications of electronic components in modern machines and automobiles. Natural convection heat transfer is preferred for electronic cooling in the unavailability of power supply or where high energy efficiency is desirable. Pin fin heat sinks offer effective cooling of such electronic devices even with the natural convection mode. Center-cleared pin-fin heat sinks offer better thermal management of a heated surface compared to conventional pin-fin heat sinks. The present work numerically investigates the thermal characteristics of center cleared solid cylinder, solid tapered, hollow tapered, and perforated hollow tapered pin fin heat sinks under natural convection. The numerical results are discussed in the form of steady state base temperature, heat transfer coefficient, mass-multiplied thermal resistance, volumetric heat dissipation rate, and effectiveness of different pin fin heat sink designs under varying power input from 2.15 to 10.75 W. The minimum mass-multiplied thermal resistance (RThM) is found to be 0.11 K.kg/W and the maximum volumetric heat dissipation rate is 1750.3 KW/m3 corresponding to the perforated hollow tapered pin fin heat sink design. [ABSTRACT FROM AUTHOR]

The application of twisted tape inserts in heat exchangers allows higher heat transfer rates with a simultaneous loss of energy due to turbulence and friction. In a conventional approach, the twisted tape is placed in the entire length of the heat exchanger. The present study explores the effect of the length of the twisted tape insert at a different twist ratio (TR) for 4700 < Re < 22,800. The insert length ratio (LR) ranges from 0.25 to 1 and the TR ranges from 1.5 to 6. The maximum Nusselt number corresponds to the LR of 0.75 at a TR of 1.5. The maximum thermo-hydraulic performance is found to be 3.2 for the LR of 0.75 at a TR of 1.5. [ABSTRACT FROM AUTHOR]

The present study examines the flow and thermal characteristics of a tube containing perforated conical inserts by varying the Reynolds number in the range of 4000–20000. The perforated conical insert having (d/D) ratio of 0.3, (p/D) ratio of 2, (x/L) ratio of 0.25, and N = 6 showed the minimum entropy generation. Second law analysis showed that the solid inserts of a lower pitch to diameter ratio are suitable to transfer high energy transfer at lower Reynold's number, whereas the perforated conical inserts are found to be effective at higher Reynolds numbers. Empirical correlations are developed for solid and perforated conical inserts. [ABSTRACT FROM AUTHOR]

Summary: The transient energy storage in a sensible energy storage system (SESS) depends on the rate of energy stored in the system. The rate of energy stored in a sensible energy system is a strong function of spatial temperature distribution that governs the energy distribution in the storage medium. The present study explores the energy and capacity factor characteristics of a wire coil fitted multi‐tubular SESS. A storage system is molded using M30 grade concrete of density (ρc= 2200 kg/m3) and specific heat capacity (Cps= 850 J/kg/K). The inlet temperature of the air, used as heat transfer fluid, is varied from 45°C to 75°C. The pitch to diameter (p/d) ratio of the wire coil insert is varied from 0.25 to 0.75 to examine its effect on energy storage/release and capacity factor. Using a (p/d) ratio of 0.5 for wire coil inserts, the maximum capacity factor of 0.98 is achieved during the charging phase of sensible energy storage at 55°C inlet air temperature and 0.029 kg/s mass flow rate of heat transfer fluid (HTF). With respect to the smooth SESS, the maximum improvement in capacity factor is found to be 29%. [ABSTRACT FROM AUTHOR]

Extended surfaces are widely investigated for their ability to enhance the heat transfer rates in different applications. Pin-fin and plate-fin heat sinks are used in a variety of cases involving a miniaturized to the large systems. The present study compares the performance of the pin-fin and the plate-fin heat sink under similar forced flow conditions. The experimental data for a modified pin fin heat sink with wings and a plate-fin heat sink with dimples are collected for the Reynolds number in the range of 6800–15100. The Nusselt number, friction factor, and thermo-hydraulic performance (THP) are examined for different geometries of the heat sink and the enhancements brought out in the heat transfer and friction are gauged relative to the smooth plate. The pin fin heat sink yields two-fold enhancement in heat transfer as compared to the plate-fin heat sink. The maximum thermo-hydraulic performance of the pin-fin heat sink with wings is found to be 4.52 at a pitch ratio (S/Df) of 2 and Wing length ratio (Lw/Df). For the plate fin heat sink with dimples, the maximum thermo-hydraulic performance is found to be 4.67 at dimple diameter ratio (D/d) of 0.5 and dimple pitch ratio (s/d) of 2.5. The correlations of the Nusselt number and friction factor are proposed for different geometries of fins. [ABSTRACT FROM AUTHOR]

Byline: Sanjith. Aaron, Sunithi. Mani, A. Prabhakar, K. Karthik, Anil Kumar. Patil, P. Babu, Mathew. Alexander Background: Strokes caused by normal variants of the cerebral circulation can be difficult to [...]

Byline: Anil Kumar. Patil, A. Prabhakar, Ajith. Sivadasan, Mathew. Alexander, Geeta. Chacko Necrotizing myopathy with pipestem capillaries is a form of chronic inflammatory myopathy, with histopathology showing necrotizing myopathy, minimal [...]