Measurements of Thermal Performance in Cooling Towers
What are Cooling Towers?
Cooling towers are commonly used in power stations, refrigeration, heating, and air conditioning industries to extract heat from a building or facility. As air enters from the sides of the tower and passes through falling water, heat is exchanged and some of the water evaporates. As a result, the heat and evaporated water rise out of the tower in the form of mist, and the cooled water accumulates at the bottom of the tower. This water can then be pumped back into the building for reuse.
This is a cost-effective and energy-efficient means for cooling large buildings such as power plants, petroleum refineries, petrochemical plants, natural gas processing plants, food processing plants, and other sizable industrial facilities where HVAC equipment would not be feasible.
What is the Importance of Measuring Cooling Tower Thermal Performance?
Each year, the Cooling Technology Institute provides a review of the previous year’s custom tower test results. This review is important because it indicates that more than half of the custom cooling tower acceptance tests are at less than 100% thermal capacity. Routine measurement of thermal performance allows owner/operators to determine how best to increase the capacity of their equipment.
The Cooling Technology Institute has developed a thermal performance guide to encourage custom tower capacity equal to or greater than 100%. Our goal is to foster and promote the benefits of thermal performance acceptance testing of water cooling towers to help owner/operators achieve ideal functionality in new and custom cooling towers as well as repacked and rebuilt towers that have a thermal guarantee.
What Does a Typical Cooling Tower Thermal Test Consist of?
Most thermal performance testing is conducted by a third-party agency using data acquisition systems to measure temperatures over a period of time. To begin, the third-party testing agency will inspect the cooling tower and identify points of measurement for the various criteria. Next, the thermal testing agency will install the necessary instruments and begin the test. Depending on the size of the tower as well as weather and operating conditions, this process can last anywhere from two hours to several days. The testing process for mechanical draft towers is typically one to two days, and natural draft towers, due to their complexity, can take anywhere from three to five days.
Once the process is underway, the testing agency will monitor the cooling tower, measuring the fan power and the rate of water flow. The following measurements will be documented:
Water flow rate
Hot water temperature
Cold water temperature
Web bulb temperature
Fan power (for mechanical draft towers)
Dry bulb temperature (for natural draft towers)
Additional data regarding tower operation may also be recorded, such as:
Pump discharge pressure
Make-up flow and temperature
Blow-down flow and temperature
Auxiliary streams entering the collection basin
How to Participate in Cooling Tower Thermal Performance Testing
Any manufacturer wishing to participate in the Cooling Technology Institute’s voluntary thermal performance testing program will need to follow the procedure listed below in order to ensure accurate results.
1. Submit an application to a CTI Administrator.
The application should include a listing of the non-custom lines and models (per STD-201) to be excluded from the custom tower program. Additionally, the application should designate a point of contact for the participating manufacturer. This contact will receive information regarding testing from the CTI Licensed Thermal Testing Agency. Upon acceptance, the CTI Administrator will provide a formal letter of acceptance to the applicant.
2. A CTI Licensed Testing Agency will conduct thermal performance testing.
To be valid, all testing must be conducted and reported by a CTI Licensed Testing Agency. Additionally, only new tower and tower repack/rebuild acceptance tests will be reported. Tests will not be considered a CTI STD-202 Reportable Test unless the participating manufacturer has been given a minimum of two weeks’ notice to attend the testing. Reportable test results will be presented to the Cooling Technology Institute as well as the designated contact for the participating manufacturer. This report will be sent no later than 30 days after the completion of the test.
3. Test results will be reported on an annual basis.
Each year, the CTI Administrator will publish a report for each participating manufacturer. This report will be available by December 1 and will include a rolling summary of the test capabilities. The performance results for each participating manufacturer will be published in each issue of the CTI journal as well as on the CTI website. Each report will include the following information:
Name of the participating manufacturer
Period of time in which the test was conducted
Percentage of test results greater than or equal to 100%
Percentage of test results greater than or equal to 95%
Average of test results that are less than 95%
Average flow rate of all tests with reported results below 50,000 GPM
Average flow rate of all tests with reported results greater than or equal to 50,000 GPM
Comparable values for all acceptance tests
4. The results of the thermal performance test will be evaluated.
For each test, the manufacturer’s guaranteed design performance for new or rebuilt custom towers shall be used to evaluate tower performance. Any participating manufacturer may choose to include or exclude specific test results from the published CTI Journal by March 1 of each year.
We Offer Independent Thermal Performance Testing
Cooling Technology Institute provides third-party, independent thermal performance testing to help participating manufacturers and owner/operators achieve the best performance from their cooling towers. Whether you have a new, custom cooling tower or a repacked/rebuilt tower, we can conduct thorough thermal testing and provide accurate results. For more information, contact us today or purchase our Standard for Publication of Custom Cooling Tower Thermal Performance Results.