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11-07-2010, 08:27 AM #1
qwestion about RH and heat rejection
Hello
The higher is the ambient air 's RH the better is heat rejection of the condenser isn't it?
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11-07-2010, 08:39 AM #2
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Re: qwestion about RH and heat rejection
I think that heat rejection of condenser is not affected with RH of air.
http://www.youtube.com/watch?v=IbVmpWvBIB0Last edited by nike123; 11-07-2010 at 08:57 AM.
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11-07-2010, 08:46 AM #3
Re: qwestion about RH and heat rejection
Incorrect, (Wrong) the higher the RH , the hgher the density (Wrong). Great SHC and heat transfer properties (Wrong)
As your fan is a fixed volume flow, then your air mass flow would increase.(Wrong)
Of course I presume we are talking about air cooled condensers.
How much of a practical difference, between 0% and 100% it could be a good few %.(Wrong)
Think of it as a bit like alltitude. Right
I AM WRONG
Sorry NikeLast edited by mad fridgie; 11-07-2010 at 09:04 AM.
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11-07-2010, 09:01 AM #4
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11-07-2010, 09:06 AM #5
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11-07-2010, 09:15 AM #6
Re: qwestion about RH and heat rejection
Mad in your own defence, you have presumed that you had a fixed volume of dry air then you added water vapour, then your density would increase, so would your pressure. Then your original presumbtions would be correct.
The question should now be asked does increase in RH change your locallised air pressure?
Mad Mad Mad (alter egos)
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11-07-2010, 09:21 AM #7
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11-07-2010, 09:25 AM #8
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11-07-2010, 10:58 AM #9
Re: qwestion about RH and heat rejection
Thank you
So, making the air, entering the condenser, more humid, wont reduce the load on the latter : heat rejection would worsen, HP would increase.Last edited by Yuri B.; 11-07-2010 at 11:01 AM.
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11-07-2010, 11:17 AM #10
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11-07-2010, 09:13 PM #11
Re: qwestion about RH and heat rejection
Yep, thats wy the make small water towers to cool down big volumes of refrig in condensors.
Have two chillers in service contract, both are of the same cooling capacity (265 KW), one has a DX condensor other one is a thirth of the sise but has a watertower to help cooling the small DX condensor. So its thru, if you add water to the air for cooling the condensor, its helps a lot. See wat happens if you have a hot summer day, and the client cals you for help because his systems trips in overheating. Take a firm hose of water and spray it over the condensor wils it is operating. You will see that everything comes back to normal.
Ice
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12-07-2010, 01:39 AM #12
Re: qwestion about RH and heat rejection
As this was such an interesting question (original), and I am free of Jack (JD), i have calculated a bit further, yes the density does drop, but the SHC does increases. The ratio is in favour of the SHC capacity, thus would very "slightly" beneifit the condenser with increased humidity.
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12-07-2010, 05:17 AM #13
Re: qwestion about RH and heat rejection
Hi there,
Almost all places which have high Rh are placed near the seas or oceans. This means sea level altitude. At this altitude air density is higher than air in higher altitude. When air density is high, air mass flow rate will be higher for the same fan. This increases the condenser performance.
BUT moisture in air does not have latent heat. If you spray liquid water on an air cooled condenser then heat transfer will be so much higher because liquid water has high latent heat.
Moisture in air already lost its latent heat.
When you calculate air cooled condenser and change RH from 10% to 90% you will see that there is negligible difference in performance.
CheersEven Einstein Asked Questions
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12-07-2010, 08:48 PM #14
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13-07-2010, 09:49 AM #15
Re: qwestion about RH and heat rejection
Spray it with hose means liquid water which has huge amount of latent heat and this will make a huge difference. We are talking about humidity of air which already lost its latent heat and became vapour.
Even Einstein Asked Questions
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13-07-2010, 12:06 PM #16
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Re: qwestion about RH and heat rejection
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19-07-2010, 05:51 AM #17
Re: qwestion about RH and heat rejection
It's hard to believe you get 40c days Ice?
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