Article Contents
As we know that cooling tower is a commonly used heat transfer equipment or we called it a heat exchanger which is for rejection of hot water heat.
In today’s article we discuss or learn more about CT efficiency , what is L / G ratio in CT , what is wet bulb temperature and how it plays a vital role in CT, what is reng in CT, percentage of water loss in CT, what is approach in CT, also we learn about blow down in C tower. Also we learn about capacity of C tower, factors which affects the performance of C tower, application of C tower.
Cooling tower
It is a heat transfer equipment which is used in all types of industry for rejection of heat (hot water heat rejection) of hot water using air. There are different types of Cooling towers available like ,
- Forced draft C tower
- Induced draft C tower
- Natural C tower
mechanical type cooling tower
- All above types are classified as based on air use, in forced draft C tower we use fan to to force the air into C tower which cool the water, in induced draft types we induce the air, and natural C tower we use only natural air for cooling the hot water.
Explain TR in details.
TR is nothing but ton of refrigeration. This is unit which measures the amount of energy required to melt or freez the water to zero degrees Celsius in period of 24 hours.In simple words ,It energy required to melt the water or freez the water.
What is TR ( ton of refrigeration )
1 TR = 1200 BTU
1 TR = 3024 Kcal/hr
What is Range in cooling towers ?
As we know that there is one inlet water and one outlet water in C tower. In C tower we send hot water as an inlet and C tower rejects the heat from that inlet hot water to the atmosphere using air and gives us cold water. Difference between inlet water to the C tower and outlet water to the tower is “Range”. In other we can say the range is nothing but the difference in the hot water and cold water temperature of a tower.
Approach in tower
Approval in towers is another most important factor or term which we need to know as a chemical engineer or mechanical engineer, which helps us in the selection or design of cooling towers.
Wet bulb temperature
In C tower design or to understand working principle of cooling tower it is necessary to understand what is wet bulb temperature.The wet bulb temperature play a vital role in design or selection of cooling water outlet water (cold water).
What is the wet bulb temperature ?
Wet bulb temperature is nothing but the temperature measured by the thermometer 🌡️ in water under ambient air condition. A tower efficiency or cooling water temperature is depende on the WBT.
Note :- when humidity is 100% then WBT ( wet bulb temperature ) become dry bulb temperature.
What is cooling tower capacity ?
Is amount of heat rejected by tower or heat transfer by tower from hot water to air by direct contact.
Cooling tower efficiency.
To calculate efficiency of tower we need to know what is reng and approach.
Efficiency of tower is nothing but ratio of range divided by (reng + approach).
Working principle of cooling tower
As we know that tower main work is reject the heat from the hot water to the hi of hot water to atmosphere.
A typical cooling tower is work on evaporation cooling principle. Now question is what is evaporation cooling ?
Evaporation cooling is nothing but evaporation and cooling happen at one time. In short cooling happen due to evaporation is nothing but evaporation cooling.
Evaporation losses in tower of cooling.
It is necessary to calculate the evaporation in tower. So evaporation can be calculated as ,
Evaporation losses in M3/3600 sec or M3 /hr is,
= 1.8 X 0.00085 X flow rate of circulating water ( T of inlet – T of outlet ).
For more details you can refer the Perry book for it. Page number is 12 to 15.
Blow Down in Cooling tower
Blow down is very important in c tower.
What is Cycle of concentration ?
Cycle of concentration is nothing but ratio of dissolved solids in cooling circulating water to the make up water.
Blow down is necessary to avoid the formation of scaling in tower. Blow down cycle can be calculated using following relationship,
Blow Down cycle = loss due to Evaporation /( COC – 1)
Conclusion
There are different types of tower for cooling hot water available, like natural draft, induced draft , forced draft. Air is use to reject the heat from hot water to atmosphere. Tower rejecte the heat on the principal of evaporation cooling. TR is the unit where we can use to decide capacity of C tower. Blow down is necessary to avoid scaling formation.we can calculate the losses of water due to evaporation. We need add or make up the water to maintain the level in tower.
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