Lamp with rigid LED strip - Design and thermal management
Investigations are connected with design and application of thermally and cost effective rigid LED strips. Standard FR 4 PCB is used for making rigid strip and LEDs are soldered on it. Special copper pins soldered underneath LEDs contribute to low thermal resistance between LEDs and heat sink - like when MCPCBs are used. Application of this type low cost rigid LED strips allows decreasing operations (and expenses) connected with assembling of LEDs onto a heat sink several times. A lamp for interior lighting is designed on the base of this type LED strips. Thermal management calculations are made and proper heat sink is chosen. Thermal loading of LEDs is experimentally tested at various ambient conditions (air temperatures from 20°C to 45°C) and different current values through LEDs - up to 600 mA. Infrared thermography is used for evaluation of temperature distribution on LEDs and heat sink. Thermal management investigations show very good qualities of developed LED strips.
Energy efficient PWM Dimmable Smart Digital LED driver
Lighting technology is progressing day by day from incandescent lamps, CFL, Induction lamps to the LEDs. LED is the future of lighting as it is having longer life greater than 50000 hours, absence of mercury, good light output, energy efficient. PWM dimming is used to control the brightness of LED. Proposed technology uses PIC16F877A microcontroller to generate PWM (Pulse Width Modulation) pulse applied as input to dimming input of constant current LED driver. Microcontroller generates PWM signal of 1.95 KHz frequency to automatically dim the LED module with respect to 24 hour. Because of which light output is reduced during the time when minimum amount of light intensity is required which results in huge energy saving. Ambient temperature is displayed on Liquid Crystal Display. Experiments are performed with various duty cycles of pulse width modulation technology and results are compared with traditional dimming technology suitable for automatic dimming feature. PWM technology possesses highest efficiency of 90 percent. It was also found that as we dim the LEDs, junction temperature also reduces which does elongates the lifetime of LED module.
Numerical and experimental investigation on air distributor design of fluidized bed reactor of sawdust pyrolysis
Abstract An improved biomass conversion in a lab-scale fluidized bed reactor (FBR) is achieved by optimizing the air distributor orifice size and number. Two approaches for introducing air were numerically and experimentally examined. These included perforated plate and downward orifice sparger. 3 mm and 5 mm orifice diameters, and 7, 9 and 13 holes were simulated at flow velocities of 2, 4, 6, and 8 times the minimum fluidization velocity, Umf. The simulation results revealed that increasing the orifice number has a positive effect on gas holdup, particularly for the perforated plate, which showed a uniform distribution of bubbles. The sparger configuration produced larger bubbles sizes, which could lead to better recirculation of solid flux, while stagnant particle zones were observed at the lower section of both distributors. A pyrolysis unit is also inserted at the top of freeboard of the FBR. For perforated plate with 6Umf, the pyrolysis process achieved thermal and cold gas efficiencies of 82.91% and 52.03%, respectively, while combustible gases with 41.6%mol CO, 8.7%mol CH 4 and 2.17%mol HC, were obtained. For sparger pipe and 6U mf _sp, 35.33 ppm NOx and 111 ppm SO 2 were measured in flue gas from combustion process at bed region.