水草情迷

Assuming the room temperature is 32C, the most powerful fan could only restore the temperature to 32C.

Bear in mind, the more equipment the more heat will be generated.

Of course a fan is helpful in cooling the extra heat caused by the lamps .. etc.

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果汁先生，風扇可以增加水嘢蒸發速度，可以有効降低水溫，中學sicence科有同樣實驗

個原理係點??
有冇人可以教下我?

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If you put some alcohol on your skin, you feel cool. The alcohol evaporates and carries your heat away. That's true.
The wind of temp 32c (room temp) blown by the fan will only saturate the surrounding substance to reach 32c.
Please correct me if I were wrong in sense.

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唏, 用風扇吹魚缸水面降溫, 已經係一個公認可行方法, 仲駛乜爭議.
果汁朋友當然冇錯啦, 你都知用酒精揮發會降低溫度啦, 依家用風扇吹水面, 都係為左加快空氣流動, 從而增加水份蒸發速度, 咪可以帶走埋魚缸熱量囉.
記住, 係吹水面, 而唔係吹玻璃呀.

No fan could lower the room temp by .00001 degree. Believe me.
Our body temp is 98.4F which is about 36.5C, and so the alcohol carries the extra heat (36.5- 32) from the skin and we feel cool. (Heat gained and heat lost)
If the room temp is 32C and the water is 30C, the temp of the water will eventualluy reach a degree of 32C.

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我投降啦, 要知真係降唔降到溫, 實際試下咪知囉, 學歷差呀, 只係知從實際經驗得返黎成果囉.


都係個句, 吹水.....面喎..

下次果汁朋友, 記得開返個 "用風扇降水溫技術研討會" 題目呀, 唔係就離晒題, 唔關把"蝸牛扇" 事啦.

我覺得阿果兄的理論"太簡單化"，
因此不能解釋得到吹水降溫的"事實"!!!!

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What you said is correct if the air are fully saturated with water i.e. relative humidity reaches 100%. In a "normal case" that the relative humidity is below 100%, increase in ventiluation can lower the water temperature. Your idea is correct if you use a fan to blow on something that will not evapourate e.g. a piece of iron.

If you still do not believe this, you may just do a small experiment to see if it works.

揮發--可在室溫中發生
即處於水面的高能量水份子, 有一定的機會率由水面走到空氣之中。若果發生這現象, 水中的能量(包括熱能), 會被那「逃走」的水份子帶走, 於是水中的總能量下降, 固此水的溫度隨之而下降。


蒸發--只可在沸點時發生
等同於「煲水」時, 水達到沸點, 於是水由液體轉變為氣體。

香港人常把揮發和蒸發混淆。

補充
如果空氣的濕度等於100%, 那就等於在水中了。

在水中不能產生"揮發"作用, 因"揮發"只能在水面發生。

魚缸水能被吹到降溫
因為, 水份子要從水面"逃走"到空氣之中, 是需要一定的機率。
處於水面的水份子, 速度越高, "逃走"到空氣之中的機會越大。
所以, 室溫越高, 水份子的能量越高, 揮發的機會越大。

總之, 有揮發的作用產生, 就可使水溫下降。

增加揮發的機會率有:
1. 將水加熱 (這個不行, 因為這連帶水的溫度也提高)
2. 增力水面和空氣之間的接觸面 (這個不行, 因為魚缸的濶度被限制。)
3. 減低空氣中的濕度 (開抽濕機/冷氣機.... )
4. 減低水面氣壓, 使水份子更易走到空氣之中 (開風扇在水面上, 水平方向吹)

100% RH would be the worst case. I hate that environment

Excuse me. This is my concept.
The difference in temperature tends to be balanced out by conduction, convertion and radiation at every moment. It finally reaches a mutual value -> same temperature.
I've tried to raise this question Dr Cho Wan Wai but the web address is not correct.
Right now I focus on the idea of providing adequate light for the plant by LED instead of creating extra heat(generated by the lamps) and then to find a way (fan solution) to carry the heat away so as to get to the room temperature.
Please feel free and do not mind. this is a way of fact finding.

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你的概念是在某情況下是對的。
讓我再補充, 熱能最終會達到平衡狀態, 除非沒有其他外加的能量。

正如我們煲水的時候, 發熱的源頭(例如火)不斷提供熱能給水, 所以水的對流並不能使水溫達到平衡。

開風扇這個動作, 已經給予空氣能量, 所以這概念並不合用。

Thnaks for your response.
Time to say good night la.
Bye.

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琉璃世界波光影 流轉逍遙逐水城
回首前塵疑是夢 迷濛醉眼羨魚情

咁你又知唔知點解在100%濕度下你會覺得"焗"？
你又信唔信出汗係可以幫身体散熱(小學常識)？
點解? Shui and Divergence 已explain 得非常詳細。
唔信？
點解自已唔做個小試驗。
查實呢D咁簡單的問題，唔洗Dr Cho，
問下你個中學physics老師都答到你。

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