Temperature of surface of cooling coil

[MrReds]

Hallo to everybody !
I am trying to calculate a cooling coil (it's fin and tube heat exchanger).
I know inlet conditions, water inlet and outlet conditions (or, alernatively, water mass flow), but I am looking for a formula to get the fin temperature.
This temperature is what I need to get the working line of the coil.
Please, can anybody give me a formula to calculate this temperature (I suppose it would be function of fin pattern), or suggest me a book or some literature where to find this formula ?

Thanks in advance

 

[MrReds]

Sorry, of course the temperature would be function of air inlet & somehow linked to the temperature of the fluid !

 

[speco]

MrReds,

You can find some calculation methods for fin temperatures in the Escoa or Wolverine literature.

However, the answer is not as simple as you might expect. The purpose of a fin is to conduct heat into or away from a tube or other surface. In an air-cooled exchanger for example, the fluid inside the tube is hotter than the cooling air. As the heat is dissipated from the tube to the air, the temperature at the base of the fin is hotter than at the tip. So, there is not one fin temperature, but a range of them for any point in the heat exchanger.

Regards,

Speco (

http://www.stoneprocess.com)

 

[MrReds]

many thanks Mr.Speco.
You are perfectly rigth,but my problem was to find the load line of a cooling coil - in order to verify if there is dehumidification or not ! -.
Concerning your suggestions, please,could you explain me
- what is Escoa
- If for Wolverine literature you mean the copper tube producer

Many thanks

 

[Lalbatros]

Since english is not my native language, I am not sure of the exact meaning of "fin and tube heat exchanger", I did not google successfully for a drawing. Sorry if my answer makes no sense. Would be interrested by a drawing.

Some time ago, I made calculations for some cross-current gas-gas tube heat exchanger. It was important to check the tube temperatures to garantee against acid-dew point condensation. I wrote a short program to be able to do this in 2D because the tube had non-uniform temperatures, the output of the tube being hotter than the input.

In the calculations, I could use empirical formula from a book (Ozisik). One formula was for the heat-tranfer coefficient inside the tube (h1). The other formula was for the heat transfer outside the tube in the cross-tube flow (h2). From the continuity of the heat flux the temperature of the tube is easily calculated: Ttube = (h1*T1+h2*T2)/(h1+h2).

I guess that you may be able to build a similar model. However some aspect may be very different or even complicate things. For example you may have free convection while I was in a forced convection case, and free-convection may be more difficult to analyse. Also, conduction within the metallic parts were negligible in my case, while they may play a role maybe for you. If it become really much more complicated, then you need a full modelling tool or a specific empirical formula.

Regards,

Michel

 

[speco]

MrReds,

Escoa is a manufacturer of finned tubes in Tulsa, Oklahoma. They have (or did have) a very useful manual for designing heat exchangers with finned tubes. Wolverine, the tube and finned tube manufacturer, also has a good manual. I believe that it is available on line.

Regards,

Speco (

http://www.stoneprocess.com)