Method for Calculating Illumination
Illumination Calculation Method:
Luminosity (Luminosity) refers to the degree to which an object is illuminated, expressed by the luminous flux received per unit area, expressed in Lux [x] (Lux, lx), that is, 1m / m2.
1 lux is equal to the illuminance when the luminous flux of 1 lumen (lumen, lm) is evenly distributed on the area of 1m2. The illuminance is based on the luminous flux received by the vertical surface, and the illuminance will decrease if it is illuminated obliquely. Calculation of illuminance The calculation methods of illuminance include utilization coefficient method, approximate curve method, specific power method and point-by-point calculation method. (1) Illumination Calculation Method Utilization Coefficient Method 1. Concept of Utilization Coefficient The utilization coefficient of the lighting source is the luminous flux projected onto the working surface (including the direct luminous flux and the luminous flux reflected from multiple directions onto the working surface) and It is represented by the ratio of the luminous flux emitted by all light sources, that is, u=φe/nφ The coefficient u is related to the following factors:
1). It is related to the type, light effect and light distribution curve of the lamp.
2). It is related to the hanging height of the lamp. The higher the suspension, the more reflected luminous flux, and the higher the utilization factor.
3). It is related to the area and shape of the room. The larger the area of the room and the closer it is to a square, the higher the utilization factor due to the more direct luminous flux.
4). It is related to the color and cleanliness of walls, ceilings and floors. The lighter the color, the cleaner the surface, the more light flux is reflected, and thus the higher the utilization factor.
2. Determination of utilization coefficient
The value of the utilization coefficient shall be determined according to the reflection coefficient of the wall and ceiling and the illuminated space characteristics of the room. The irradiated space characteristics of the room are characterized by a parameter of "room cabin rate" (abbreviated as RCR). A room can be divided into three spaces according to different lighting conditions: the top is the ceiling space, the floor space is below the working surface, and the middle part is called the room space. There is no ceiling space for rooms with ceiling lights or recessed lighting, and no floor space for rooms with ground-level work surfaces. Room space ratio RCR=5hRC(l+b)/lb: where hRC--room space height; l--room length; b--room width. According to the reflection coefficient of the wall and ceiling (see Table 8-1) and the room space ratio RCR, the utilization coefficient can be found from the corresponding lamp utilization coefficient table.
3. Calculate the average illuminance on the working surface according to the utilization coefficient method
During the use of the lamps, the luminous efficiency of the light source itself will gradually decrease, the lamps will also be old and dirty, and the walls and ceilings of the illuminated places may also be stained, thereby reducing the luminous flux on the working surface, so in the calculation work When calculating the actual average illuminance on the surface, a "light reduction coefficient" less than 1 should be included. Therefore, the actual average illuminance on the working surface is Eav=uKnφ/A where u____utilization coefficient; K____ dimming coefficient (also known as maintenance coefficient), the reference values are listed in Table 8-3; n____number of lamps; φ____luminous flux emitted by each lamp; A____area of the illuminated room.
