| Smoke detector is an important part of the fire system,which is of great significance to the prevention of fire.The photoelectric smoke sensor detects whether the fire has occurred and emits an alarm according to the intensity of the scattered light of smoke particles,which has the advantages of simple structure and low price.However,there is a defect of false alarm in high humidity environments such as coal mines and underground pipelines.In view of this phenomenon,a method of heating and area dehumidification to avoid false alarm in the photoelectric smoke sensor was proposed.The main research contents of the thesis are as follows:(1)A heater was placed at the bottom of an optical maze to heat and dehumidify the smoke detector model.The analysis of the relative humidity and condensation inside the optical smoke detector before and after the regional heating and dehumidification showed that condensation occurred inside the smoke detector before heating,and the temperature increase affected the saturation vapor pressure in the wet air,thus affecting the relative humidity inside the smoke detector,and the maximum relative humidity inside was maintained below the saturation value after regional heating,effectively avoiding the occurrence of condensation.(2)A thin film electric heater was designed to reduce the humidity inside the detector,and was optimized for low power consumption.The heating performance of thin film electric heaters made of stainless steel,nickel-chromium alloy and iron-nickel alloy was compared,and it was concluded that iron-nickel alloy had fast thermal response speed,obvious local energy concentration and obvious positive temperature coefficient characteristics.Subsequently,COMSOL software was used to optimize the power according to the substrate material,wiring and heating wire thickness of the thin film electric heater.At present,the optimal power of the heater with heating and dehumidifying anti-condensation effect is 0.12 W.(3)The thin film electric heater and the regional dehumidifying optical smoke detector were tested.The results show that the actual temperature and resistance of the thin film electric heater are within the acceptable range compared with the design,and the relative humidity inside the smoke detector is reduced by about 15% through regional dehumidification,effectively preventing condensation inside the optical smoke detector and reducing the false alarm rate of the optical smoke detector.Through regional heating and dehumidification technology,the optical smoke sensor can be free from the influence of condensation misreport,and has a very important application value in special environments requiring precise and reliable,such as coal mines and underground pipeline galleries.This technology can effectively enhance the reliability of the smoke sensor,thereby helping to monitor and control the environment. |
