How to Choose cooling tower solutions?

Imagine sitting in an important work meeting, but you can’t concentrate because there’s an irritating rushing noise erupting from the heating, ventilation, and air conditioning (HVAC) system.

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Or perhaps you’re enjoying the beautiful sounds of an acoustic concert, and the concert hall starts getting warmer and warmer as the cooling tower stopped working properly causing the concert to be cut short.

Typical causes of theses issues often come from the complicated air moving systems in some cooling towers. Many businesses across the United States use water to cool their buildings, so any malfunctions like these are crucial to prevent.

Thanks to advanced technology, a cooling tower doesn’t have to cause these problems. But how do you choose a cooling tower that is efficient and suitable for your business?

After all, not all towers are right for all applications. Cooling towers aren’t created equally, and there are many different types available.

Knowing and understanding the various types, and their benefits and disadvantages are crucial when choosing a cooling tower. That’s where we come in to help.

Here’s our essential guide to choosing the best type of cooling tower for your business.

Choose the Right Size

When choosing a HVAC or industrial cooling tower, the appropriate size must be selected to maximize its benefits. Cooling towers are a considerably affordable and effective way of reducing heat from various industrial processes, so size must be considered. Cooling towers come in many sizes and are used for nuclear and thermal power plants, petrochemical plants, food processing plants, petroleum refineries, and HVAC systems.

As cooling towers are used in more and more applications worldwide because of their most cost effective solution to remove heat, the concern of size becomes more important. How big should a cooling tower be to support an application as efficiently as possible?

There are plenty of applications and processes where choosing an undersized cooling tower would be detrimental to the business.

If an undersized cooling tower isn’t providing enough cold water to cool the condenser loop of an office’s HVAC system, then the chiller could shut down and stop working. This is likely to lead to pricey repairs and plenty of annoyed and angry staff members or tenants.

An insufficient cooling tower capacity can lead to severe damage to expensive processing equipment. Of course, a shut down on this scale can lead to significant losses in productivity. With most applications, determining and understanding the minimum size a cooling tower should be is crucial.

For most wet cooling towers, the ideal size can be understood by a combination of four metrics. These are heat load, approach, range, and wet bulb temperature.  Most manufacturers have sizing programs to determine the minimum size cooling tower needed.

To understand how these metrics affect the size of a cooling tower, it’s essential to learn some context.

The wet bulb temperature (WBT) of the air flowing into the cooling tower in is a separate variable that determines the most suitable size of a cooling tower.

When selecting the size of a cooling tower, remember that the highest WBT should be used for sizing purposes.  This ensures the cooling tower works sufficiently on the most humid day of the year.

Assess Efficiency

Ensuring cooling tower efficiency is essential when choosing one. In many towers, especially the wet metal-clad types, cooling efficiency is affected when aggressive chemical solutions are limited due to the risk of harm and damage to metal surfaces.

Plus, having to limit potent chemicals used to remove biological growth from water can produce fouling build-up inside the cooling tower. This affects cooling efficiency.

Water cooling towers made of high density polyethylene (HDPE) plastic are becoming increasingly popular. Towers made from HDPE can treat the water more aggressively with the necessary chemical treatments required. Business owners don’t have to worry about any corrosion issues.

The corrosives found in saltwater, air, or the atmosphere of many industrial sites often damage metal-clad cooling towers. This makes them less efficient and susceptible to maintenance and unscheduled shutdowns. But HDPE cooling towers are resistant to corrosion.

As HDPE cooling towers are unaffected by such corrosives, they don’t need much maintenance, and they offer a much longer life.

Delta cooling towers all offer a 20-year warranty, so you can rest assured that your cooling tower investment is worth the money.

Cooling tower efficiency is also determined by tower footprint. Some businesses select a tower with a smaller footprint to allow for more space for other items. However, that decision typically requires using more power to drive the tower fans to satisfy the cooling load.

Saving energy is essential for many brands, so a cooling tower with a bigger footprint that uses a lot less power may be the more efficient and worthwhile choice.

Consider Noise

As mentioned, the noise a cooling tower emits is essential to consider. Many older cooling towers are so loud that they sound like an airplane is passing overhead. As you can imagine, this isn’t effective for productivity, especially in an office building.

Fortunately, many cooling towers are fitted with new technology to reduce noise significantly. Always consider the noise levels when selecting a cooling tower for your business.

Don't Forget the Design

The design of the cooling tower is essential to consider too, and this links in with efficiency. As mentioned, cooling towers made of HDPE are particularly useful.

Here at Delta Cooling Towers, we are a pioneer in this technology. It was originally used to correct corrosion issues resulting from industrial gases, routine chemical water treatments, and salt air affecting metal towers.

Cooling tower fan options that decrease maintenance issues are direct-driven. This feature means you don’t have to concern yourself regarding gearbox or belt-driven systems failures.  These maintenance items invariably result in costly downtime for an industrial process or lost HVAC cooling in a commercial business.

Direct-drive fans reduce operational issues and maintenance works. A VFD selection for controling the fan speed allows for continuous and consistent water temperatures and energy savings.

Some businesses choose to run at 50% power during a season of operation. This reduces energy usage and expenditure.

Consider the Origin of Manufacturer

Many businesses are interested to know where their cooling tower is produced. Will it be made in the manufacturer’s premises? Or is it outsourced to foreign subcontractors?

In the latter situation, more assurance is often required regarding the quality of the cooling tower and how business owners are affected if replacement parts are needed in the future.

In many cases, cooling towers are shipped unassembled to businesses and then reassembled by local labor. If you decide to go for this option, don’t expect the quality as you would from a cooling tower assembled in the manufacturers’ plant by knowledgeable and skilled factory workers.

This process is used by suppliers that outsource the entire production of cooling towers. However, the cost savings made in shipping don’t cover the expenses and issues that many clients experience after time with the towers assembled onsite by people who are unfamiliar with the model. Plus, local laborers are often working in more challenging conditions.

Are You Ready to Choose a Cooling Tower?

If you’re considering investing in a cooling tower for your business, consider consulting with an experienced cooling tower engineer before completing a plan to purchase a cooling tower for a business.

Find Your Optimal Cooling Tower Type

As the technology-leading cooling tower manufacturer, Delta’s cooling tower designs last longer, save on costs and eliminate downtime, translating to an unrivaled lifecycle. So, there’s no need to worry about replacements. And, Delta’s product quality is backed by a 20-year warranty. To learn more, contact Delta today. Click here!

Explore Delta’s Cooling Tower Sizing Calculator

To determine the perfect cooling tower design and size for your needs, Delta makes it easy with our downloadable sizing program. To discover Delta’s cooling tower sizing & selection program, simply click here.

Narrowing Down Your Cooling Tower Selection

If you are interested in learning the methods of determining the proper size cooling tower, rest assured that Delta is here with guidance. Explore our handy information. Click here to learn about sizing & selecting.

Know Your Cooling Tower Capacity Calculation

Whether your application is for industrial process cooling or HVAC condenser cooling, the data required is the same. The following design data is required for cooling tower sizing to properly select the appropriate model:

• Flow Rate in GPM
• Range of cooling in °F (T1 – T2)
• Area Wet Bulb Temperature in °F (Twb)
  
  

Cooling Tower Heat Load Calculation

The Design Heat Load is determined by the Flow Rate, and the Range of cooling, and is calculated using the following formula:

Heat Load (BTU/Hr) = GPM X 500 X Range (T1 – T2) °F

If the range of cooling, Heat Load, and one of the other two factors are known (either the GPM or the ° Range of cooling), the other can be calculated using this formula.

• GPM = Heat Load (BTU/Hr) / 500 X ° Range of cooling
• ° Range of cooling = Heat Load (BTU/Hr) / 500 X GPM The Design GPM and the °
  
  

The range of cooling is directly proportional to the Heat Load.

Let Us Help You With Cooling Tower Sizing & Selecting

How comfortable are you working up a cooling tower selection?

The cooling tower selection table may look confusing, but after you have made a few selections, the process is straightforward. If you need a refresher, this may help. The following design data is required to select cooling towers:

Flow Rate in GPM

Range of cooling in °F (T1 - T2)

Area Wet Bulb Temperature in °F (Twb)

The Design Heat Load is determined by the Flow Rate, and the Range of cooling, and is calculated using the following formula: Heat Load (BTU/Hr) = GPM X 500 X ° Range of cooling.

More importantly, if the Heat Load and one of the other two factors are known, either the GPM or the ° Range of cooling, the other can be calculated using this formula.

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For example: GPM = Heat Load (BTU/Hr), or 500 X ° Range of cooling ° Range of cooling = Heat Load (BTU/Hr) 500 X GPM

So, as you can see, the Design GPM and the ° Range of cooling, are directly proportional to the Heat Load.

And, 500 is the “fluid factor” which is based on water as the heat transfer fluid. The fluid factor is obtained by using the weight of a gallon of water (8.33 lbs.) multiplied by the specific heat of the water (1.0) multiplied by 60 (minutes/hour).

The first step in selecting a cooling tower is to determine the Nominal cooling tower load. Since a cooling tower ton is based on 15,000 BTU/Hr, the formula is:

Nominal Load = GPM X 500 (Constant) X ° Range of cooling, 15,000 BTU/Hr/Ton or, the more simplified version of the same formula, Nominal Load = GPM X ° Range of cooling 30

More on Sizing & Selecting

Examples of Different Applications

Once the Nominal cooling load has been calculated, a Correction Factor must be determined to calculate the Actual Rated cooling tower tons required for the specific conditions of service. The correction factor adjusts for the ease or difficulty of cooling based on the Theoretical Design of all cooling towers.

The Nominal Ton Correction Factor is determined by using the COUNTERFLOW COOLING TOWER SELECTION AND PERFORMANCE CHART enclosed. Note that the curves are shown as three separate sections. The WET BULB CORRECTION SECTION, the APPROACH SECTION, and the CAPACITY MULTIPLIER FACTOR SECTION. First, find the Range line in the WET BULB CORRECTION SECTION in the upper left-hand section of the chart. Move along the Range line over to the intersection of the Wet Bulb line.

Now move down along the Wet Bulb line to the APPROACH SECTION, in the lower left-hand section of the chart, and stop at the intersection of the Approach line. Move across to the CAPACITY MULTIPLIER FACTOR SECTION to the right-hand curves and stop at the intersection of the Range line and read the CAPACITY MULTIPLIER FACTOR.

The Actual Rated cooling tower tons can now be calculated by multiplying the Nominal cooling tons, which was previously calculated, by the CAPACITY MULTIPLIER FACTOR. The Actual Rated cooling tower tons is the capacity required for the specific conditions of service, and the next largest size cooling tower should be selected for the application.

Following are selection examples for three different applications. One example is based on conditions that are identified as "Theoretical Design," for reasons which will become apparent.

The second example, entitled "Actual Design" is a selection based on adjusting from Theoretical to Actual design.

The third example, "Modified Application", converts an actual once-through well water system to a cooling tower recirculation system.

Sizing & Selecting

Read on to Learn about the Cooling Tower Selection Procedure

Example 1. Theoretical Design

The following conditions are provided for selection purposes:

The operating water flow rate is 600 GPM.

Hot water temperature (T1) to the cooling tower is 95° F.

Cold water temperature (T2) desired from the cooling tower is 85° F.

The installation location's wet bulb temperature (Twb) is 78° F.

You can now make a cooling tower selection with this information:

The water flow is 600 GPM. The Range of cooling is 10° - (T1 - T2). The Approach to the wet bulb temperature is 7° - (T2 - Twb).

First the cooling tower NOMINAL load has to be determined:

Nominal Load = GPM x 500 x ° Range, = GPM x ° Range, therefore, 15,000 BTU/Hr 30

Nominal Load = 600 gpm x 10° Range = 200 tons of cooling required.

30 Since the Heat Load = Flow (gpm) x 500 x °Range of cooling= 600 gpm x 500 x 10° = 3,000,000 BTU/Hr and a cooling tower nominal ton = 15,000 BTU/Hr, the nominal cooling tower ton is derived from the actual heat load. Therefore, a heat load of 3,000,000 BTU/Hr = 200 nominal cooling tower tons.

Now the Nominal Ton Correction Factor has to be determined for the conditions established:

A 10° Range of cooling, and a 7° Approach to the design wet bulb temperature of 78°F, using the COUNTERFLOW COOLING TOWER SELECTION AND PERFORMANCE CHART enclosed.

Find the 10° Range line in the WET BULB CORRECTION SECTION in the upper left-hand section of the chart. Move along the 10° Range line over to the intersection of the 78° Wet Bulb line.

Move down along the 78° Wet Bulb line to the APPROACH SECTION, (the lower left-hand section), and stop at the intersection of the 7° Approach line.

Move across to the CAPACITY MULTIPLIER FACTOR SECTION to the right-hand curve and stop at the intersection of the 10°Range line, and read the CAPACITY MULTIPLIER FACTOR, which is 1.0.

To select the proper cooling tower for this application, multiply the 200 Nominal tons calculated, by the 1.0 CAPACITY FACTOR. As previously stated, the correction factor adjusts for the ease or difficulty of cooling in relation to the Theoretical Design. So in this case, since the CAPACITY CORRECTION FACTOR is 1.0, the Nominal and Actual Rated tons are the same as the Theoretical Design, and a Model DT-200I cooling tower can be quoted. 

Sizing & Selecting

Cooling Tower Selection Procedure

Example 2. Actual Design

Now we will select a cooling tower for the same 200-ton Nominal Load as Example #1 but is different from the Theoretical Design. The operating water flow rate is 300 GPM.

Hot water temperature (T1) to the cooling tower is 105° F.

Cold water temperature (T2) desired from the cooling tower is 85° F. The installation location's wet bulb temperature (Twb) is 76° F.

You can now make a cooling tower selection with this information:

The water flow is 300 GPM. The Range of cooling is 20° - (T1 - T2). The Approach to the wet bulb temperature is 9° - (T2 - Twb).

First, the cooling tower NOMINAL load must be determined:

Nominal Load = GPM x 500 x ° Range, = GPM x ° Range; therefore, 15,000 BTU/Hr 30.  Nominal Load = 300 gpm x 20° Range = 200 cooling tons required.  30 Since the Heat Load = Flow (gpm) x 500 x °Range of cooling= 300 gpm x 500 x 20° = 3,000,000 BTU/Hr and a cooling tower nominal ton = 15,000 BTU/Hr, the Nominal cooling tower ton is derived from the actual Heat Load. Again, a 3,000,000 BTU/Hr heat load = 200 Nominal cooling tower tons.

Now the Nominal Ton Correction Factor must be determined for the conditions established; a 20° Range of cooling, and a 9° Approach to the design wet bulb temperature of 76°F, using the COUNTERFLOW COOLING TOWER SELECTION AND PERFORMANCE CHART enclosed.

First, find the 20° Range line in the WET BULB CORRECTION SECTION in the upper left-hand section of the chart. Move along the 20° Range line over to the intersection of the 76° Wet Bulb line. Move down along the 76° Wet Bulb line to the APPROACH SECTION, in the lower left-hand section of the chart, and stop at the intersection of the 9° Approach line. Move across to the CAPACITY MULTIPLIER FACTOR SECTION to the right-hand curves and stop at the intersection of the 20° Range line, and read the CAPACITY MULTIPLIER FACTOR, which in this case is 0.62.

The final step to select the proper cooling tower for this application is to multiply the 200 nominal cooling tons required, which was calculated above, by the CAPACITY FACTOR, which in this case is 0.62. The cooling tower Actual Rated tons for the conditions given are therefore 124 tons, and a Model DT-125I cooling tower can be quoted. Since the correction factor adjusts for the ease or difficulty of cooling based on the Theoretical Design, in this case, the Actual Rated tower conditions are easier than Theoretical Design.

Sizing & Selecting

Cooling Tower Selection Procedure

3. Modified Application

The following is an example of modifying a "once through non-recirculating cooling application" to a recirculating cooling tower system. A cooling tower is required for heat exchanger process cooling, which is now being cooled using 55°F well water at a flow rate of (1 Million gallons/day - 300,000 sanitary = 700,000 gal per day).

Approximately 500 GPM, and discharging to a lake at 80°F. With this information we can establish the Heat Load, which is 500 GPM x 500 x 25° R (80°F - 55°F) = 6,250,000 Btu/Hr.

We can establish the cooling tower design for a 6,250,000 Btu/Hr Heat Load based on the installation location design Twb, which, for this example, we'll say is determined to be 76°F, and by establishing a reasonable cold water temperature at a 7° Approach to the Twb, at 83°F.

What we have to determine now is either the design range of cooling or the appropriate design flow rate based on the established Heat Load. Let’s select the appropriate design flow rate by using a reasonable 15° Range of cooling; 83°F cold water + 15° = 98°F hot water.

Use the Cooling Tower Heat Load Calculation to find the design flow rate as follows:

Heat Load (BTU/Hr) = GPM X 500 X ° Range of cooling, or rearranged to determine the design flow rate. GPM = Heat Load (BTU/Hr) = 6,250,000 Btu/Hr = 835 gpm 500 X ° Range of cooling 500 x 15° R Now you can make your cooling tower selection based on 835 gpm, cooling from 98°F to 83°F @ a design 76°F Twb. The cooling tower selection is = 418 Nominal Tons x .83 DCF = 347 Rated cooling tower tons, or a 350-ton cooling tower selection.

Alternate #1:

A commercial cooling tower can also be selected for this heat load based on a 25° Range of cooling. The conditions for selection would be 500 GPM, cooling from 108°F to 83°F @ 76°F Twb, which is equal to 418 Nominal tons x .62 DCF = 259 Rated cooling tower tons, for a 260 ton cooling tower requirement.

Alternate #2:

Or select for a design to cool 110°F to 83°F = 27° R of cooling, the design flow would be 6,250,000 Btu/Hr = 465 GPM. 27° R x 500

The selection for 465 GPM cooling from 110°F to 83°F @ 76°F Twb = 418 Nominal tons x .58 DCF = 242 Rated tons; so you can recommend a single Model DT-250I cooling tower.

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