The cooling tower experiment measures how effectively a cooling tower lowers water temperature by evaporative cooling, evaluated through three quantities, range, approach, and cooling efficiency. It is a key heat-transfer and thermal-engineering practical, because cooling towers reject waste heat in power plants, HVAC systems, and process industries.
Aim of the experiment
To study the performance of a cooling tower and determine its range, approach, and cooling efficiency.
Theory
A cooling tower cools warm water by bringing it into contact with air, so a small fraction of the water evaporates and carries away latent heat. Performance is judged by three quantities:
- Range = T₁ − T₂ (hot water inlet temperature minus cooled water outlet temperature)
- Approach = T₂ − Twb (cooled water outlet temperature minus the wet-bulb temperature of the inlet air)
- Cooling efficiency η = (T₁ − T₂) / (T₁ − Twb) = Range / (Range + Approach)
The wet-bulb temperature is the theoretical lowest temperature to which the water can be cooled; a smaller approach means a more effective tower.
Apparatus required
- Laboratory forced/induced-draft cooling tower test rig
- Water heater, circulating pump and flow meter
- Blower/fan with air-flow measurement
- Dry-bulb and wet-bulb thermometers (air inlet/outlet) and water inlet/outlet thermometers
Procedure
- Fill the sump and start water circulation; switch on the heater to set the inlet water temperature.
- Start the fan and allow conditions to stabilise.
- Record inlet and outlet water temperatures, air dry-bulb and wet-bulb temperatures, and the water and air flow rates.
- Compute range, approach, and cooling efficiency.
- Repeat at different air-flow rates or heat loads and plot efficiency against the air/water ratio.
Result
Cooling efficiency rises with air flow up to a point, and the approach shrinks as air–water contact improves. Typical laboratory tower efficiency is 70–90%.
Applications
Cooling towers serve thermal power stations, HVAC chillers, refrigeration condensers, and process cooling. This links to the cooling side of the IC engine performance test, and complements the double-pipe heat exchanger and natural & forced convection experiments. See related terms in the engineering lab glossary.
Frequently asked questions
What is range and approach in a cooling tower?
Range is the temperature drop of the water (T₁ − T₂); approach is how close the cooled water gets to the air wet-bulb temperature (T₂ − Twb).
Why can’t water be cooled below the wet-bulb temperature?
The wet-bulb temperature is the thermodynamic limit of evaporative cooling, so the cooled water can only approach it, never go below it.
What is a good cooling tower efficiency?
Most towers operate at 70–90%; a smaller approach indicates better performance.
Need a cooling tower test rig for your heat-transfer lab? Request a quote from Scientico India, ISO 9001:2015 certified, CE marked, exporting to 60+ countries, reply within 24 hours.
Specify the cooling-tower trainer by the readings students need
Range and approach require reliable water and air temperature measurements at defined locations. A useful trainer must also make water flow and air-flow conditions controllable or observable. The enquiry should name the calculations and operating variations required rather than requesting a generic bench-top cooling tower.
What to confirm before requesting a quotation
- Confirm dry-bulb, wet-bulb and water-temperature measuring locations.
- Define water-flow and air-flow control or indication.
- List packing, heater/load arrangement, tank, pump and make-up-water scope.
- State ventilation, drainage, electrical and laboratory-space constraints.
For an international order, also state the quantity, destination, electrical supply, documentation, installation or training needs and requested delivery basis. Treat catalogue information as a starting point; the current model page, datasheet and written quotation must confirm the exact configuration.
Cooling tower trainer: readings, controls and site readiness
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