As a way to measurement a cooling tower, you might want to know your course of move (gallons per minute) and provide and return fluid temperatures. Additionally, you will must know the wet bulb and ambient temperatures for the area the place you might be located. Use the charts under to measurement your cooling tower. Notice the model numbers don’t reference air-conditioning tons.
To find out your wet bulb and ambient, discuss with the chart beneath.
Humidity and Cooling Towers
The map at the appropriate illustrates dry climates and low humidity areas as 1 and a couple of against the humid areas of 3 and 4.
Areas three and 4 are very humid and evaporative coolers are about half as efficient here as in areas 1 and a pair of.
When a Chiller and Tower Sizing are equal
In areas 1 and a pair of a cooling tower will most likely reject as many BTU’s per ton of score as a chiller. If, then, a machine wants a 10 ton chiller it can in all probability carry out equally with a 10 ton tower.
The identical machine in areas three and 4 will usually require a tower twice as big because the chiller, because of the factor we name wet bulb temperature.
The wet bulb temperature is defined as that temperature that the ambient temperature ( dry bulb temperature ) and the relative humidity working collectively make happen. It’s not theoretical; it is very real. Hot is just not a foul factor for evaporation. In reality, evaporation could be very rapid within the desert ( Las Vegas @ 71° W.B. ) at 100°. Humidity works towards the heat, however, and retards the evaporation rate. A median humidity of eighty five% will cut back the speed by at least half.
Evaporation Cools the Water
Cooling towers are engineered to evaporate shifting water because it passes over PVC or other materials and air is blown by way of it. The more evaporation that takes place, the better the cooling.
The straightforward explanation is that when water modifications state from a liquid to a gasoline it consumes BTU’s, or heat. Evaporation of a pound of water will consume almost 1,000 Btu’s. That loss of heat will change the temperature of the water left behind, barely.
Chiller vs. tower
By design, cooling towers are high circulation charge gadgets. Nominal circulate rates of two.5 to 3.Zero gallons/ ton/minute are normal. The 10 ton chiller can even circulate approximately 2.5 gpm/ton, and since it is mechanically cooled with refrigeration, the nominal cooling is 8 to 10 degrees each time a gallon of water passes by means of the heat exchanger.
Ideally, our cooling tower would match that, and it’ll in areas 1 and a pair of more often than not. Un luckily, in areas three and four, the wet bulb temperatures are a lot higher and in the peak of summer time when it’s scorching and humid at the identical time, the tower may solely cool that gallon of water 2 or three levels F each move through the tower. Chillers, then, are a huge benefit at these times.
Install bigger towers to compensate!
The norm in areas 3 and four is: Tower Size = 2 x Chiller Size. If an application calls for a 10 ton chiller, a 20 ton cooling tower is advisable. The net result’s that by transferring twice the water ( circulation rate ) the diminished temperature drop will be compensated for by cooling the water twice, as a substitute of as soon as.
Level of no return
When ( not if ) the wet bulb temperature is higher ( it is hot and humid! ) the ability of the tower no matter tower size is less. I t doesn’t matter if you happen to set up a a hundred ton tower and circulate 300 gallons per minute, if the wet bulb temperature is 77°, the perfect you may get is probably 3° to 5° above that, or 80° to 82°. The desk under lists some main U.S. cities with the design dry bulb and wet bulb temperature scores as listed by the American Refrigeration Institute. Add a number of levels to the wet bulb and you’ll have the coolest water temperature attainable in the worst summer months. Put another manner, the wet bulb temperature is that worst ( hottest )
temperature attainable; and ninety seven% of the time it will likely be cooler.
The bottom line is to have the ability to cope with those times when wet bulb is the very best or to consider using a chiller instead of a cooling tower if your course of doesn’t allow for variation (essential cooling processes).
Upkeep of towers
Reality 1: Upkeep is crucial to the environment friendly operation of Cooling Towers.
Fact 2: The higher cooling towers work (evaporate water) the dirtier towers become and the more maintenance they require.
Reality 3: From the primary minute a brand new tower goes online, it begins to lose efficiency and the ability to cool. This is one other reason to oversize them to keep up cooling capability as they age.
You’ll be able to see from the desk that if the humidity is low ( Las Vegas or Phoenix ) and the dry bulb ( ambient ) temperature is excessive ( 100°F + ) the cooling means of a tower may be very, excellent. That 71° wet bulb in Las Vegas means the tower will yield 75° or cooler water 97% of the time. Even when it is 106°F within the shade! And never many towers are within the shade in Las Vegas.
I personally measured a roof top temperature of 157° at 2:30 p.m. once! And don’t tell me “Yea, however it is a dry heat!It was bloody scorching! But, the tower was producing 65° water!
On the other hand, that very same tower had to be replaced every three years as a result of the buildup of minerals turned it into a brick actual fast.
Look at Tampa @ 80° and Pensacola @ 81°, with a dry bulb of 90° and 91°, respectively. Not solely is the humidity so thick you’ll be able to minimize it with a knife however it’s also sizzling. And that isn’t a dry heat! No marvel that a tower can solely produce 95° water in the peak of summer. The faucet ( ground ) water is 85°.
When does a cooling tower turns into a water heater?
Assuming, you may have 75° water popping out of the process, and also you ship it to a cooling tower since you need 65° , what temperature will you get back? Answer: Within the case of the Tampa tower above, 95°degrees!
This dispels the assumption that a refrigeration coil within the tank is a good “boosteror supplement for the tower. A helper chiller can be utilized, but not by placing a coil within the tank. It could take a 12.5 ton chiller to “helpa 10 ton tower by 10° that means! It all will get right down to wet bulb and flow rates and Btu’s and pounds per minute and horsepower.
If in case you have questions on sizing your cooling tower or a cooling downside for which you
need help, be at liberty to contact us. We might be pleased to assist you!