諗唔到

dye 2011/2/15 11:02

本帖最後由 dye 於 2011/2/15 11:05 編輯

Sorry, I do not believe what the web site is saying.

Here is an experiment Sherman can do and help us understand the question:

Place the candle further and further away from the hair blower and see the effect.  (Test the air pressure.  The further the wind source, the smaller the low pressure.)

Use this distance, change the temerature of the wind blowing, perhaps by using the fridge and heating element of the dair dryer.  (Test for temperature.  Is it true that people in Arctic has an easier time blowing out candle than say, African?)

Lastly, to proof what the web site is correct, it should be impossible to blow out a lighter because you can't "blow off" the flame.  So change the fire source and try it again to see if there is any difference!

抽刀斷水 2011/2/15 11:29

根據http://www.tutorvista.com/conten ... sion/combustion.php，燃燒的conditions如下：
1. 物質本身可燃
2. 氧氣
3. 溫度

那吹氣令其熄滅，究竟是令溫度下降是主因，抑或令氧氣的密度降低（降低氣壓）呢？

我猜用風筒吹，經過風筒發熱線後，部分氧氣就會燃燒走，所以沙文的實驗方法是有問題的。

最好是：

用一個氧氣筒，將氧氣加熱後向火柴或蠟燭噴出，咁就perfect喇！（不過實驗危險性高，建議沙文先立遺囑，到自己活得不耐煩時才進行）

dye 2011/2/15 11:56

本帖最後由 dye 於 2011/2/15 11:58 編輯

Are you sure the electric heating element of the hair dryer will "burn" any oxygen away?  How about a safer way with air from freezer, or air from top of a block of ice?  If temperature is an issue, cooler air should be able to do it better, right?

Actually I found an even more likely answer, it fits with all observations I seen so far in my life:

I think the wind blow the chain reaction of the fire away.  In order for the flame to continue, the last reaction must be in proximity with the next reaction in order to transfer the heat.

With the air moving so fast, it outpace the reaction front.

This is observable as the wind gets stronger and stronger, the flame moves away from the head.  At certain wind speed, the flame will bound to be too far from the fuel source.

**  I think the temperature idea is correct only concerning candle because of the way the fuel is supplied (vapourization of the wax).  It is incorrect in the general sense.

沙文 2011/2/16 10:41

回復 424# dye
Thx dye, your explaination seems make more sense 2 me.
但為了慎重起見, 我仍會在滿月宴上進行該項實驗

沙文 2011/9/20 23:25

影相發燒友參加攝影比賽，題目係「大自然」
我的拍友影這張相參賽：