消防常识

雷电是雷云放电的一种自然现象。雷电引起火灾大致有这几种情况: 直击雷 电流直接击在建筑物上,雷电流产生强热能,能引起可燃物和化学危险品燃烧、爆炸。 感应雷 又称间接雷击或雷电的二次作用。

Characteristics of radiation and convection heat transfer in indirect near-infrared-ray heating chamber

Numerical study was performed to evaluate the characteristics of combined heat transfer of radiation, conduction and convection in indirect near infrared ray （N/R） heating chamber. The effects of important design parameters such as the shape of heat absorbing cylinder and heat releasing fin on the pressure drop and heat transfer coefficient were analyzed with different Reynolds numbers. The Reynolds numbers were varied from 103 to 3x106, which was defined based on the hydraulic diameter of the heat absorbing cylinder. Analyses were performed to obtain the inner and outer flow and the temperature distributions in the heat absorbing cylinder and the rates of radiation heat transfer and convection heat transfer. As the Reynolds number increases, the convection heat transfer rate is increased while the radiation heat transfer rate is decreased. The average convection heat transfer rate follows a power rule of the Reynolds number. Addition of three-dimensional heat releasing fin to the outside of the heat absorbing cylinder enhances the convection heat transfer.

钓鱼谨防遭雷击

许多钓迷垂钓时,经常遇有大雨滂沱雷鸣闪电。近几年来,有些钓迷在雷雨季节遭受雷击的事例并不鲜见。