Considering the characteristic of energy-saving about high power LED device, a method to decrease the junction
temperature greatly under the natural convection condition is studied in this article. Using the heat pipe technology, a cooling system is designed in which the target heat source is the LED module (0.025m×0.025m×0.005m), with 30W input power. The mechanism and routes of heat transfer are analyzed in detail, the thermal network model is established to calculate the thermal resistance of each part in the cooling system, the total thermal resistance was calculated to be 0.8964°C /W and the junction temperature was 47.39°C . Meanwhile, the finite element method was used to simulate this cooling system, and got that the junction temperature was 47.54°C , and the error of the two means is only 0.15°C , it indicates that applying heat-pipe technology can solve the problem of high junction temperature in LED devices under the natural convection conditions, which can guide the actual project in the thermal design.
A detecting system is developed applying the technologies of fiber-optic sensing, grating dispersion and multi-channel image sensing (Charge Coupled Device) based on the fluorescence mechanism of carbaryl. In this system, a pulsed xenon lamp is used as an excitation light source, optical fibers are selected to transmit and detect fluorescence, fluorescence dispersion is implemented with a small-sized flat field grating spectrometer and data gathering and A/D conversion are conducted with a high speed signal processing module. Moreover, the system is used to measure the fluorescence characteristics of carbaryl. The results show that a full fluorescence spectrum of carbaryl can be obtained in a single exposure under a UV excitation wavelength of 319nm, has a good linear relationship in the range of 4.0~100.0 ng/mL of carbaryl liquor and the minimum detecting limit is 4.0ng/mL with the linear correlation coefficient r being 0.9986. When this instrument is likewise applied for measuring carbaryl in river and ground water,the recovery may approach 100 %.
We report our research on the development of optical fiber trace gas sensors for environmental applications. A novel optical fiber sensor for monitoring acetylene (C2H2) gases is described. Through studying the measure theory, we use the Beer-Lambert law to monitor the gas. And after analyzing the C2H2 spectrum, we select Distributed Feedback Laser Diode (DFB LD) as light source. Comparing many kinds’ sensor detection head, the gas absorbing cell with tail fiber can have good coupling with optical fiber and improve the coupling stability. In the data processing system, signals are distilled by lock-in amplifiers and then harmonic measure technology processes that distilled faint signals. After the all, the electronic signals are transmitted into computer to process, alarm and display. We design the instrument who can remote and on-line measuring acetylene. Through theory analysis and system experiment, the design of the system is practicable, and has a better precision and some apply foreground.
At present, many floater-type measurement equipments whose readings are recorded by manpower are still in use in petrol-chemical industries. With regard to their low efficiency, great errors and their improbability in realization in automation management and remote control, in this instance, a new liquid-level meter system using the advanced fiber-optic sensing technology based on the floater-type level meter is developed. In principle, it measures the liquid level of the oil tank by using the principle of force balance, captures and transmits the light signals by means of the fiber-optic sensing technology, adjusts the light signals from continuous impulse signals to the discontinuous by the light-code disc, then converts light impulses into voltage impulses by photoelectric elements. In configuration, it adopts a twin light source and a twin optical-channel, utilizes twin fiber detectors to record the size of the liquid level and judge the direction of the liquid level respectively. Moreover, the measuring system has been tested practically in a chemical plant, the results indicate that the measuring errors are Less than or equal to ±6mm, relative errors are <2% when its measuring range is within 0 and 1000mm.It is proved that the various indexes of the system satisfies the demand of the industries and the capability is credible.