COOLING TOWER DESIGN

[AQUASANJ]

I AM ASKED TO DESIGN A COOLING TOWER FOR AN ICE CREAM FACTORY.THEY WISH TO RECIRCULATE THE WATER WHICH COOLS THE ICE CREAM MIX IN 7 DIFFERENT TYPES OF MACHINES.THE INCOMING TEMPERATURE AT THE COOLING TOWER IS ESTIMATED AT 45 DEGREES CENIGRADE AND SHOULD COOL THE WATER TO AT LEAST +18 DEGREES.
APPROXIMATE WATER FLOW THROUGH THE MACHINES IS 4000 LITRES PER HOUR.COULD YOU PLEASE ADVISE HOW I MAY GO ABOUT THIS.HAVE THOUGHT OF A CHILLER SYSTEM BUT CLIENT HAS A LIMITED BUDGET.

 

[quark]

Aquasanj!

First of all let me clear you one thing. You cannot theoretically cool water in a cooling tower below the wet bulb temperature of the air. And practically, the best cooling tower I have used has an Approach(cooling water outlet temperature - wet bulb temperature) of
3⁰C. i.e. if your area wet bulb temperature is
25⁰C then the cooling water outlet temperature at best will be 28⁰C.

The capacity of cooling tower is given by the formula
Q = mCp(T1-T2) where m is mass flow rate of water in Kg/hr or any other unit. Cp is specific heat
(1kCal/Kg⁰C. T1 is water entering temperature and T2 is water leaving temperature in degree centigrade.

In your case it is 4000x1x27 = 108000kCal/hr = 35.72TR or
428640 Btu/Hr (1 TR = 3024kCal/Hr and 12000 Btu/Hr) provided if your area design wet bulb temperature is 3deg.C below the temperature you required.

And this is not all. Go and check this site for clarification of some fundamentals.

http://myhome.hanafos.com/~criok/english/publication/thermal/thermallisteng.html

If blank page is appearing after going to this site click
Back button and then Forward button and the page will appear, and same procedure for all the pages.

 

[stevenw]

A cooling tower will not cool the water to that cold.
I suggest a large insulated water tank and a small chiller.
The chiller would run continously to cool the tank.

 

[Koske]

Usually in food processing industry they use plate heat exchangers, for that kind applications. Personally i don't think that cooling tower is good solution for something like that, because you will have very little control over your procees.

 

[rintin]

Depending the wet bulb temperature in your area, probably you can't cold the water until 18°c. You have to use a chiller. But chiller is more expensive than cooling tower.
You can use a combined system cooling tower + chiller. Thus select a smaller chiller
First in a cooling tower you can cold the water from 45°C to 28°C (This temperature depends on your wet bulb temperature, here I suppose it's 25°C), in second step you can cold this water from 28°C to 18°C by a chiller.

Your total cooling capacity is 108,000 kcal/h
In cooling tower, you get 68,000 kcal/h, and in chiller 40,000 kcal/h.

Thus you can buy 40,000 kcal/h chiller,(not 108,000 kcal/h)

Here you need 1 pcs 40,000 kcal/h chiller
1 pcs 68,000 kcal/h cooling tower. If your chiller is water cooled, you must select bigger cooling tower (68,000 + 40,000 x 1,25 = 118,000 kcal/h or over)

As you know, the cooling towers are open to the atmosphere, therefore it's adviced to use plate heat exchangers between tower and chiller, tower and ice machines

 

[VEEKRISH]

Quark, thanks for the tip about thee site. fantastic site. Really useful. Now I know all there is to know about cooling tower design. Thanks again.