68 degree centigrade needs to break the red bulb in the fire sprinkler.
The glass bulb inside a fire sprinkler head is filled with a heat sensitive liquid (e.g., glycerine) that expands faster than the glass bulb as it gets hotter. Eventually, it expands so much that it causes the glass bulb to burst, releasing the water behind it.The different colors of liquid contained within the bulb correlate to the temperature at which the sprinkler head will activate:Orange - 135oFRed - 155oFYellow - 174oFGreen - 200oFBlue - 286oFPurple - 360oFBlack - 440OFDifferent colors are used in different environments depending on the average ambient heat in said environment. For instance, if you have a storage facility that needs to be kept at temperatures higher than 135 F, you can imagine why you wouldn't want a orange-bulbed fire sprinkler!
modern automatic sprinklers use a glass bulb that is filled with a fluid that boils and expands at a preset temperature. the glass bulb has a small bubble in the fluid. when a fire causes the fluid to boil, it shatters the glass bulb, which is keeping the waterway seal of the sprinkler in place. When the seal is gone, water can flow through the sprinkler orfice, and extinguish the fire. older sprinkler models use a link and lever arrangement, with a link of solder that melts at a preset temperature. The link and levers of the sprinkler mechanically hold the waterway seal of the sprinkler closed. When the link melts, the mechanical seal is gone, and water can flow through the orfice.
It depends on the temperature rating of the particular bulb, but all bulbs are filled with aproprietary glycerin liquid.
The most common fire sprinkler system is a wet pipe system wich always has water in it. The sprinkler heads have a heat sensitive element, most commonly a glass bulb filled with liquid that expand when exposed to heat, after a certain temperature is met , usually 160 degrees or more the glass bulb breaks and allows water to flow on the fire in a uniform water density. The sprinkler system may have an alarm device that sounds an audible alarm in the building, and/or call the fire department. The system may have a connection for the fire department to add to the automatic water supply. there are other types of systems, dry-pipe, preaction, and others which are similar but do not have water in the piping initally due to concerns of freezing water in the system, or sensitive areas where accidental water damage would be a greater problem than fire.(museums, computer rooms, etc)
When wet bulb temperature and dry bulb temperature are equal, it means that the air is saturated with water vapor and cannot hold any more moisture. This condition is known as 100% relative humidity. It is a key indicator of atmospheric stability and is used in meteorology to determine the potential for cloud formation and precipitation.
The wet-bulb depression (WBD) is the difference in temperature between the ambient air temperature (Ta) and the wet-bulb temperature (Tw), ie: WBD = (Ta-Tw), and is associated with the maximum possible lowering of air temperature (hence, the word "depression") that's possible by evaporation of water vapor into the air up to the 100% relative humidity point.
The wet bulb temperature is always lower than the dry bulb temperature. The wet bulb temperature is the temperature taken by a thermometer covered in a wet cloth and exposed to moving air, and it reflects the evaporative cooling effect.
the evaporation off the moisture on the wet bulb absorbs the heat.
Bulb temperature is typically lower than dry temperature because the bulb thermometer measures the temperature of the air without factoring in the effects of evaporation. The dry bulb temperature, on the other hand, accounts for the cooling effect of evaporation, giving a lower reading than the bulb temperature.
it is difference between wet bulb temperature and dry bulb temperature.
The bulb of a thermometer is usually made of glass to allow for expansion and contraction of the liquid inside. When the thermometer is subject to sudden changes in temperature, the glass can crack or shatter due to thermal stress, causing the bulb to break.
the "current" temperature, ie, the temperature at which wet bulb and dry bulb are the same. when the wet bulb and dry bulb temperaturs equalized the dew point emperature equals them, because the air is saturated now.