1. Humidification and evaporative cooling
Agor, Gregori Jan
Langaman, Jerielyn
Agustin, Crystal
Mapolon, April
Fontanilla, Rose Ann
5ChE-B

2. Introduction
Cooling towers are heat rejection devices which usually transfer heat from hot water towards a moving stream of air typically in a counter flow direction.
It involve mass transfer through the evaporation of water into the moving air stream causing an increase in the absolute humidity and the temperature of the air.

3. Objectives

4. objectives
To apply the principles of humidification and evaporative cooling in the shell-and-tube heat exchange-cooling tower network in the laboratory.
To study the parts of an induced draft, counter flow cooling tower and their uses.
To estimate the number of transfer units and height o a transfer unit of the tower.

5. Table 1 shows the water and air conditions measured during the experimentation process.

6. Calculations: Liquid Entering Flowrate (Entering) ρ = 991.7937 kg/m3
Liquid leaving Flowrate (Leaving)
ρ = kg/m3

7. Calculations Mass of Dry Air: Mass Balance:
For Entering Air: tw1 = OC pw1 = kPa t1 = 29.78OC
PA1 = x10-4[ (28.58)] *(29.78—28.58) = kPa
H1 = =
For Exiting Air: tw1 = OC pw1 = kPa t1 = 29.26OC
PA1 = x10-4[ (28.06)] *(29.26—28.06) = kPa
H2 = =

8. Calculations
G =

9. Treated Data

10. Calculations
HTU
K’a
Heat Load

11. Results and Discussions

12. Table 1 shows the water and air conditions measured during the experimentation process.

13. The range and the 5.8 approach obtained from the experiment implies a relatively poor performance of the tower.
The cooling factor obtained x10-3 means that the liquid flowrate is smaller than the gas flowrate.
A high range indicates great capacity of the tower to cool the water
A low approach means large heat loss is achieved by the water.
The performance of a cooling tower is influenced mainly by wet bulb temperature of the moist air entering and the ratio of water and air mass flow rate as described by the cooling factor or L/G ratio.
Cooling factor is the limiting coefficient for the mass transfer to take place.
For stage-wise operations, the minimum value of cooling factor would yield into an infinite number of plates therefore cooling towers should never be operated under these conditions.

14. For NTU, the most common method which is employed in obtaining a value of for this experiment is the iterative integration.
The HTU obtained from the experiment is The mass transfer coefficient calculated is x10-9 while the heat load of the tower is KJ. This values are significantly low compared to normal operating conditions of a mechanically induced cooling towers.
NTU measures the difficulty separation between the water vapor and the air mixture.
HTU gives the separation effectiveness of the packings use and it is a function of the air flow rate and the mass transfer coefficient.
A high value of HTU results in a higher tower and a more efficient packing.

15. ANSWERS TO QUESTIONS
How does the number of transfer units affect the cooling factor?
NTU - Measure of the difficulty of separation between the water and air mixture
Cooling Factor - Minimum required coefficient

16. ANSWERS TO QUESTIONS
How does the number of transfer units affect the cooling factor?
NTU= 𝑘 𝑎 ′𝑉 𝐿 ; 𝐿 𝐺
NTU decreases with increase in L/G

17. ANSWERS TO QUESTIONS
Given that the boiler will be supplying steam to several equipment such as heat exchanger and dryers present in the laboratory,
a. How would the operation of cooling tower be affected?
b. What parameters would be affected?
Since the boiler supplies steam to different equipment in the lab, the steam that passes through the pipeline experience pressure drop and the fluid velocity also changes due to flow resistances.
The temperature of the water entering the cooling tower would be lower if the flow rate of the water entering the heat exchanger is held constant and the steam flowrate decreases.
The steam distribution present in the laboratory affects different parameters in the process. Given that boiler supplies to equipment other than the heat exchanger means steam passes through branched pipework and therefore experience pressure drops and changes in fluid velocity due to resistance flow or friction.

18. ANSWERS TO QUESTIONS
Given that the boiler will be supplying steam to several equipment such as heat exchanger and dryers present in the laboratory,
How would the operation of cooling tower be affected?
b. What parameters would be affected?
It is possible that the steam has encountered heat losses along the pipeline even before the cooling tower
Range and approach of the tower would change
The steam distribution present in the laboratory affects different parameters in the process. Given that boiler supplies to equipment other than the heat exchanger means steam passes through branched pipework and therefore experience pressure drops and changes in fluid velocity due to resistance flow or friction.

19. Conclusion
Cooling factor (3.349× 10 −3 ), range (4.42°C ) and approach (8.1°C) obtained did not meet the literature values for a cooling tower system.
Cooling tower system has low efficiency in terms of evaporative cooling.
The estimated values of NTU and heat load were 0.52 and kJ. The HTU was
The temperature of exiting water was oC from the wet bulb temperature of entering air of oC.
High range – high capacity to cool the water
and low approach – abt zero means large heat loss is achieved by the water.
Typical values for NTU in mechanically induced cooling towers ranges from 1-2.

20. Recommendation Steam flow rate should be controlled properly.
Make sure that equipment is free from any form of damage and leaks.
Replace the rotameter.
Counter-current Flow for the cooling tower

21. THANK YOU