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Are You Still Buying Cooling Towers as per TR Capacity?
Cooling Tower Guide
Are You Still Buying Cooling Towers as per TR Capacity?
Published by Wetpoint Aqua Equipment Pvt Ltd · Gwalior, India
Most owners, plant managers, project in-charges and engineers ask for a cooling tower the same way: “Please quote a 200 TR cooling tower.” Most suppliers answer in the same unit, because TR is the most common term in the cooling tower industry.
The habit is convenient, but for industrial process cooling it hides the information that decides whether the tower will actually work. A TR figure does not tell the manufacturer what temperature your machine needs, what the weather at your site allows, or how large the tower must be to bridge the two. Wetpoint explains why TR falls short and what to ask for instead.
Why TR Became the Default Way to Ask for a Cooling Tower
TR (tons of refrigeration) is the standard unit for air-conditioning and refrigeration equipment. Chillers and condensing units are rated in TR, so the cooling towers that serve them are rated in TR as well.
Over time the unit spread to every other segment of industry. Buyers carry it over from HVAC projects, consultants repeat it in tender documents, and suppliers quote in it because the customer asked for it. Nobody questions it, and that is where the problems begin.
Where TR Works: Air-Conditioning and Refrigeration Applications
TR is meant for air-conditioning and refrigeration, where the capacity of the machine itself is stated in TR. A cooling tower for a chiller plant or a refrigeration unit therefore comes naturally in TR capacity, because the heat load follows from the machine rating.
If your tower serves a central AC plant, a TR-based enquiry is acceptable. Even then, the wet bulb temperature of your location should be stated, because it affects tower size.
Why TR Fails for Industrial Process Cooling
Process cooling loads, such as those in automobile component plants and chemical plants, do not behave like a chiller. Each machine has its own hot water and cold water temperature requirement. Designing a cooling tower in TR for these applications leads to one of two outcomes:
1. The tower falls short
The tower does not deliver the cold water the machine needs. The temperature drop across the tower falls short, so the machine runs hotter. This increases wear and tear on the equipment you are trying to protect.
2. The tower is oversized
The tower is oversized to compensate. A larger fan motor and water pump then draw more power every hour the plant runs. The extra running cost makes your investment ineffective.
Heat Rejection Capacity Alone Is Also Incomplete
Some engineers and consultants specify the heat rejection capacity of the tower instead of TR. This is better in one way, because it reflects the real heat load. It is still only part of the story.
A cooling tower works by transferring heat from process water to atmospheric air. How hard that transfer is depends on the condition of the air at your site and on how cold you need the water to be. Two towers with the same heat rejection can be very different in size and cost.
Approach: The Parameter That Decides Cooling Tower Size
Approach is the cold water temperature minus the wet bulb temperature. Range is the hot water temperature minus the cold water temperature. Heat rejection comes from flow and range: flow in m³/h × 1,000 × range in °C gives kcal/h.
The example below shows two towers with the same heat load and very different designs:
| Plant A | Plant B | |
|---|---|---|
| Water flow | 100 m³/h | 100 m³/h |
| Hot / cold water temperature | 36°C / 31°C | 38°C / 33°C |
| Range | 5°C | 5°C |
| Wet bulb temperature | 27°C | 27°C |
| Approach | 4°C | 6°C |
| Heat rejection | 5,00,000 kcal/h | 5,00,000 kcal/h |
| Tower size | Larger | Smaller |
Both plants reject the same heat, so both would get the same TR figure in a quote. But Plant A needs colder water relative to the air, so its tower needs more fill surface area and a larger fan diameter, with more fan power. A low approach means a bigger tower. That is why the cold water requirement matters as much as the load.
Buying by TR vs Buying by Process Data: Advantages and Disadvantages
Neither method is wrong in every case. What matters is whether it fits your application. Here is how they compare.
Buying by TR
Advantages
- Simple to ask for. One number is enough to start an enquiry.
- Familiar to everyone, from consultants to suppliers.
- Suitable for air-conditioning and refrigeration duty, where the machine itself is rated in TR.
Disadvantages
- The design conditions behind the TR figure are hidden, so you do not know the approach, range or wet bulb temperature the supplier assumed.
- For process cooling, it can give lower efficiency: either a small temperature drop that increases wear and tear on the machine, or higher fan motor and pump power.
- Quotes from different suppliers cannot be compared fairly, because the same TR can mean towers of different sizes.
Buying by Process Data
Advantages
- The tower is designed for your machine’s actual hot and cold water temperatures.
- Fan and pump power are matched to the duty, so running costs are lower and the investment pays back as intended.
- Quotes are comparable because every supplier works from the same stated conditions.
Disadvantages
- You need to collect six data points before asking for a quote.
- It takes a little more time at the enquiry stage, and your process or utilities team may need to supply the figures.
- A low approach requirement increases tower size and cost, so the real price of a tight temperature becomes visible. This is a benefit for your decision, but it can feel like a disadvantage at first.
What Wet Point’s Expert Suggest
Our engineers recommend that you stop asking for a quote in TR unless the tower serves an air-conditioning or refrigeration plant. For every process cooling enquiry, send the supplier the data below and ask them to state the approach and design wet bulb temperature in the quote.
At Wet Point, every tower is sized from this data, and the six points that follow are exactly what we ask for.
The 6 Data Points to Give Your Supplier Instead of TR
Most suppliers quote in TR because customers ask for it. Stop asking for a quote in TR, and give the following data instead:
1
Water flow rate
Water flow rate of process water to be cooled. With the range, this sets the heat load.
2
Hot water temperature
Hot water temperature leaving the machine. This is the inlet temperature to the tower.
3
Cold water temperature
Cold water temperature required by the machine. This sets the approach and has the biggest effect on tower size.
4
Wet bulb temperature
Wet bulb temperature of the area. Use the design wet bulb for your site, not the dry bulb.
5
Water quality
Water quality of process water. It influences the fill selection and the choice of materials.
6
Space constraints
Space or site area constraints, if any. Available footprint and height affect the tower configuration.
How to Check a Supplier’s Quote Against These Parameters
Before you compare prices, check that every quote answers these questions:
- Does it state the hot water, cold water and wet bulb design temperatures, not just a TR figure?
- Does it state the water flow rate in m³/h?
- Does it list the fan motor and pump power, so running costs can be compared?
- Is the stated approach realistic for the wet bulb temperature of your site?
- Does it state the fill area and tower size?
Quotes are only comparable when they are based on the same design conditions.
FAQs
Only for air-conditioning and refrigeration applications. For industrial process cooling, no. Specify the water flow, hot and cold water temperatures and wet bulb temperature instead.
TR is a rating unit that comes from air-conditioning and refrigeration. Heat rejection is the actual heat removed from the water, calculated from flow and range. Approach is the cold water temperature minus the wet bulb temperature, and it decides how large the tower must be.
Water flow rate, hot water temperature, required cold water temperature, wet bulb temperature of the site, water quality and any space constraints.
Each supplier assumes different design conditions behind the TR number, such as a different approach, range or wet bulb temperature. Towers of different sizes then carry the same TR label. Ask every supplier to quote on identical stated conditions.
Get a Quote Based on Your Process Data
If you are unsure about any of these points, contact a Wet Point representative by WhatsApp, email or call. Wet Point has manufactured cooling towers in Gwalior since 1996 and sizes each tower from your process data.
Wetpoint Aqua Equipment Pvt Ltd
736, Ganga Malanpur, Morena Link Road, Gwalior-474002
Phone: 9302214784 (call or WhatsApp)
736, Ganga Malanpur, Morena Link Road, Gwalior-474002
Phone: 9302214784 (call or WhatsApp)
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