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IS 13723:2018 is the Indian Standard (BIS) for cooling towers - method of test. This standard specifies the methods for conducting thermal performance tests on water cooling towers. It outlines the required instrumentation, test procedures, and calculation methods to determine the tower's cooling capability and verify its performance against design specifications.
Specifies methods for testing the thermal performance of mechanical draught counter-flow and cross-flow cooling towers.
! Ensure all instruments are calibrated as per Table 1 before starting the test, as even small errors in wet-bulb temperature can significantly affect results.
! Achieving stable operating conditions before starting the official 1-hour test run is critical for data validity. Monitor water flow, heat load, and fan power closely.
! Environmental factors like wind speed, recirculation, and interference from other sources can heavily influence test results. Select test conditions and locations carefully to minimize these effects as per Clause 5.3.
CTI ATC-105(22)Cooling Technology Institute (CTI), USA
HighCurrent
Acceptance Test Code for Water-Cooling Towers
Defines procedures and instrumentation for field acceptance testing to verify thermal performance of cooling towers.
ASME PTC 23-2019American Society of Mechanical Engineers (ASME), USA
HighCurrent
Performance Test Codes: Atmospheric Water-Cooling Equipment
Provides rigorous methods for testing the thermal performance of various types of water cooling towers.
VDI 2042 Part 1:2019Verein Deutscher Ingenieure (VDI), Germany
MediumCurrent
Acceptance and performance tests on cooling tower systems - Fundamentals and test definitions (VDI-Kühlturmregeln)
Specifies rules and methods for performance and acceptance tests of cooling tower systems, with some procedural differences.
BS EN 14705:2005British Standards Institution (BSI), UK / European Committee for Standardization (CEN)
MediumCurrent
Heat exchangers. Method of measurement and evaluation of thermal performance of wet cooling towers
Provides a method for measuring and evaluating the thermal performance, sharing principles but differing in some test details.
Key Differences
≠IS 13723 specifies a required air velocity over the wet-bulb psychrometer wick of 3.5 to 5.5 m/s, whereas CTI ATC-105 requires a higher and more specific velocity of 6.1 to 7.6 m/s (1200 to 1500 ft/min).
≠While IS 13723 relies on the individual accuracy of instruments, ASME PTC 23 explicitly states a goal for the overall test uncertainty (approximately ±5%) and provides methodologies for its calculation, which is a more holistic approach.
≠IS 13723 references other Indian Standards (e.g., IS 5241) for specific procedures like water flow measurement, creating a dependency on the national standards ecosystem. In contrast, CTI and ASME codes are more self-contained or reference their own series of standards.
Key Similarities
≈All standards are based on the same fundamental test objective: to determine the tower's 'capability' by comparing the actual performance to the design performance under a specific set of operating conditions.
≈The core thermal analysis in IS 13723 and its international counterparts is based on Merkel's theory, using the concept of enthalpy difference as the driving force for heat and mass transfer.
≈All standards mandate strict criteria for test stability, requiring key parameters like water flow rate, temperatures, and ambient wet-bulb temperature to remain within specified narrow limits for the duration of the test.
≈The types of instrumentation required for primary measurements (water temperatures, water flow rate, wet-bulb temperature) are fundamentally the same, focusing on high-precision devices like calibrated thermometers, differential pressure flow meters, and mechanically-aspirated psychrometers.
Parameter Comparison
Parameter
IS Value
International
Source
Psychrometer Aspiration Velocity
3.5 to 5.5 m/s
6.1 to 7.6 m/s (1200 to 1500 ft/min)
CTI ATC-105(22)
Water Temperature Instrument Accuracy
Accurate to within ±0.05 °C
Readable to 0.1°F (≈0.056°C) and calibrated to an accuracy of ±0.1°F
CTI ATC-105(22)
Hot Water Temperature Stability
Variation not to exceed ±0.3 °C from the average
Variation not to exceed ±0.5°F (±0.28°C) from the average
CTI ATC-105(22)
Water Flow Rate Stability
Variation not to exceed ±2% from the average
Variation not to exceed ±2% from the average
CTI ATC-105(22)
Maximum Allowable Wind Speed
Test should not be conducted if wind speed exceeds 4.5 m/s
Test should be avoided if average wind exceeds 10 mph (4.5 m/s), unless all parties agree
ASME PTC 23-2019
Wet-Bulb Temperature Measurement Location
1.5 m above the basin curb at the geometric center of the air inlet
1.2 m to 1.8 m (4 ft to 6 ft) above the basin curb, centered on the air inlet face
CTI ATC-105(22)
Overall Test Uncertainty Goal
Not explicitly stated as a single target value; determined by instrument accuracy.
The procedures are designed to yield a result with an uncertainty of approximately ±5%.
ASME PTC 23-2019
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Maximum permissible error for Wet Bulb Temperature measurement± 0.1 °C
Maximum permissible error for water flow rate measurement± 2.0 percent
Minimum test duration after stabilization1 hour
Maximum deviation of water flow rate during test± 2 percent of average
Maximum deviation of heat load during test± 5 percent of average
Maximum variation in entering wet-bulb temperature during test± 1.0 °C from average
Key Formulas
Heat Rejection, Q = L × Cpw × (T1 - T2) — Heat load calculation from water side
Tower Characteristic, KaV/L = ∫(T2 to T1) dT / (hw - ha) — Merkel's method for tower capability
Water Evaporation Rate, E = G × (w2 - w1) — Calculation of water loss due to evaporation
Tables & Referenced Sections
Key Tables
Table 1 - Maximum Permissible Error for Instruments