Air cool condenser in humid climate

[A.Mortezania]

Dear Friends,

As you know air-cool condenser works better in humid climate.

1 - It is as result of vaporizing water drops on surface of fin ?

Or

2 - It is as result of higher mass flow of air (in humid climate instead dry climate) that pass form fins ?

Which answer is correct ?

Sincerely yours.

[chemi-cool]

Non, humidity does not affect condensers.

[A.Mortezania]

Non, humidity does not affect condensers.

Dear Chemi-Cool,

Be sure and I promise you humidity effects on working of air-cool condensers.

Sincerely yours.

[PaulZ]

Hi Mortezania
Can you explain how an increase in humidity will improve the performance of an air cooled condenser and what percentage performance increase would be achieved.
Regards
Paul

[mad fridgie]

Dear Friends,

As you know air-cool condenser works better in humid climate.

1 - It is as result of vaporizing water drops on surface of fin ?

Or

2 - It is as result of higher mass flow of air (in humid climate instead dry climate) that pass form fins ?

Which answer is correct ?

Sincerely yours.

It is presumed that the air pressure and dry bulb temperature is a constant and the only change is RH (moisture content)

1,no,the H2O is already in vapour form

2 Incorrect, density decrease with increase in RH (lower mass flow), however specific heat capacity raises slightly, so calculation is neutral. (well within the normal range of accuracy and fouling factor)

[A.Mortezania]

It is presumed that the air pressure and dry bulb temperature is a constant and the only change is RH (moisture content)

1,no,the H2O is already in vapour form

2 Incorrect, density decrease with increase in RH (lower mass flow), however specific heat capacity raises slightly, so calculation is neutral. (well within the normal range of accuracy and fouling factor)

Dear Fridgie,
Thanks for your reply.

I searched internet, Yes , You are right. By increasing RH , Density of air decrease !!! and in this case I made big mistake.

Please do me a favor and help to understand this matter better :
We have 2 cities :

City 1 : Avg. temp = 35 C , Altitude = 1200 m , humidity = 30%
City 2 : Avg. temp = 35 C , Altitude = 50 m , Humidity = 85%

We have 2 cities in our countries above, Temperature is almost same, But I saw it by my eyes that condenser in city with 85% humidity works much more better instead city with humidity 30% and discharge pressure is lower at same system.

Yes, It is true that by increasing humidity, Density decreases, By this fact, What really change between these 2 cities ???
Altitude changes ? Dry bulb changes ? Wet bulb changes ? Specific of air changes ? What really changes that help condenser to works better in city with higher humidity ?

Thanks for your help in advance.

Sincerely yours.

[mad fridgie]

Dear Fridgie,
Thanks for your reply.

I searched internet, Yes , You are right. By increasing RH , Density of air decrease !!! and in this case I made big mistake.

Please do me a favor and help to understand this matter better :
We have 2 cities :

City 1 : Avg. temp = 35 C , Altitude = 1200 m , humidity = 30%
City 2 : Avg. temp = 35 C , Altitude = 50 m , Humidity = 85%

We have 2 cities in our countries above, Temperature is almost same, But I saw it by my eyes that condenser in city with 85% humidity works much more better instead city with humidity 30% and discharge pressure is lower at same system.

Yes, It is true that by increasing humidity, Density decreases, By this fact, What really change between these 2 cities ???
Altitude changes ? Dry bulb changes ? Wet bulb changes ? Specific of air changes ? What really changes that help condenser to works better in city with higher humidity ?

Thanks for your help in advance.

Sincerely yours.
Altitude!
Air heat exchangers are de-rated for altitude. Reduced Mass Flow!

[A.Mortezania]

Altitude!
Air heat exchangers are de-rated for altitude. Reduced Mass Flow!

ِ
Dear Fridgie,
Thanks for your reply.

Ok, Altitude is good subject that influences air density.

Regarding increasing humidity and decreasing density, As I told you before, Yes, You are right but density changing around air temp : 20C ~ 40C is not high ! (See my diagram below)

1 - I saw that by increasing humidity enthalpy of air change. It will not help us ?

2 - What about C parameter in Q = M.C.(T2 – T1) , My mean specific heat ?
If we increase humidity on air, Twice specific heat would be constant ???
Do you have any chart or document to prove this ? I didn't find anything on internet.


14622



Sincerely yours.

[mad fridgie]

Change in specific heat is also minimal (not twice) at working temperatures, balances with reduction in density, so calculation in neutral, in practice. Fin coil has a design tolerance, so these small changes are within the standard production performance tolerances. Do not worry about it. Move on.

[botrous]

Hi
You better check your indoor (evaporating unit) performance and relate it to the condenser performance,
the way you are trying to relate things will not lead to any useful answer.

Same units, same indoor conditions, same load , different outdoor humidity,than you can have a peer to peer comparison.

Indoor load will directly affect the condenser performance.

regards

[douglas8]

I am not quite sure about it.