Basic Water Cooling Tower Essay Example

Student Name/Number:

Basic Water Cooling Tower

Exercise A: Observation of the processes occurring within a forced draught cooling tower

The variables are measured as below:

Temperature of water entering at the top of packing,
Basic Water Cooling Tower = 40oC

Temperature of water leaving at the bottom of packing,
Basic Water Cooling Tower 1 = 27.4oC

Temperature of air leaving at the top of packing (dry bulb),
Basic Water Cooling Tower 2 = 23.1oC

Temperature of air entering the bottom of packing (dry bulb),Basic Water Cooling Tower 3 = 21.4oC

Relative humidity of air entering at the bottom, RH2 = 40.6%

Relative humidity of air leaving at the bottom, RH1 = 97.3%

Power required to heat water (cooling load) = 1.0 kW

Temperature of air in,
Basic Water Cooling Tower 4= 12.68oC

Temperature of air out,
Basic Water Cooling Tower 5= 21.07oC

Calculations:

Basic Water Cooling Tower 6Basic Water Cooling Tower 7

Basic Water Cooling Tower 8

Basic Water Cooling Tower 9

Basic Water Cooling Tower 10

Basic Water Cooling Tower 11

Basic Water Cooling Tower 12=
Basic Water Cooling Tower 13

Exercise B: Effect of water inlet temperature on the performance of the cooling tower

The measured values, and calculated values of Approach, Range, and Effectiveness are shown in the table below:

Table 1(a): Effect of water inlet temperature on effectiveness

Water inlet temperature (Basic Water Cooling Tower 14)

T2 = Tw out

T4 = Ta out

RH1 = Rh out (%)

RH2 = Rh in

Cooling load (kW)

Table 1(b): Comparing performance at each water temperature

Water inlet temperature (Basic Water Cooling Tower 15)

Range (Basic Water Cooling Tower 16)

Approach valueBasic Water Cooling Tower 17

Cooling load kW

Effectiveness %

The graph of (i) Range vs. Twin, (ii) Approach vs. Twin, (iii) Effective vs. Twin, and (iv) Cooling load vs. Twin.

  1. Range vs. Twin

Basic Water Cooling Tower 18

Figure 1 (a): Graph of Range vs. Twin

  1. Approach value vs.
    Twin

Basic Water Cooling Tower 19

Figure 1(b): Graph of Approach vs. Twin

  1. Cooling load vs. Twin

Basic Water Cooling Tower 20

Figure 1(c): Graph of cooling load vs. Twin

  1. Effectiveness vs. Twin

Basic Water Cooling Tower 21

Figure 1(d): Graph of effectiveness vs. Twin

Basic Water Cooling Tower 22

Figure 1(e): Graph of cooling load vs. approach

In figure 1(a), 1(b) and 1(c), range, approach and cooling load increases with increase in the temperature of inlet water. Increasing the temperature of the water inlet means that more energy will be used to raise the temperature of the water, and a larger temperature difference is created between the cooling air and the water, which increases the rate of heat transfer. From figure 1(d), effectiveness is maximum at 30oC and 45.2oC respectively, but minimum at temperatures between the two values. This can be attributed to the temperature difference created between cooling air and water. In figure 1(e), a higher cooling load is required for a higher approach. Increase in approach means increase in range, which in turn needs more energy to raise the temperature of water.

Exercise C: Effect of air flow rate on the performance of the cooling tower

The measured values, and calculated values of Approach, Range, and Effectiveness are shown in the table below:

Table 2 (a): Effect of air flow rate on effectiveness

Air flow l/sec

T2 = Tw out

T3 = Ta out

RH1 = Rh out (%)

RH2 = Rh in

Table 1(b): Comparing performance at each Air flow rate

Air flow l/sec

Approach valueBasic Water Cooling Tower 23

RangeBasic Water Cooling Tower 24

Cooling load kW

Effectiveness %

  1. Range vs. airflow rate

Basic Water Cooling Tower 25

Figure 2(a): Range vs. airflow rate

  1. Approach vs. airflow rate

Basic Water Cooling Tower 26

Figure 2(b): Approach vs. airflow rate

  1. Cooling load vs. airflow rate

Basic Water Cooling Tower 27

Figure 2(c): Cooling load vs. airflow rate

  1. Effectiveness vs. airflow rate

Basic Water Cooling Tower 28

Figure 2(d): Effectiveness vs. Airflow rate

  1. Approach vs. cooling load

Basic Water Cooling Tower 29

Figure 2(e): Approach vs. cooling load

From the graph in figure 2(a), 2(c) and 2(d), range, cooling load and effectiveness increases with increase in the rate of airflow. In figure 2(b) and 2(e), approach decreases with the rate of air flow rate and decrease in the cooling load respectively. Increase in the range increases effectiveness of the cooling tower, while decrease in the approach increases the effectiveness. Thus, the decrease in approach with increasing airflow increases the performance of the cooling tower. As more air passes through the fills, the cooling effect is increased.

Reference

Armfield Ltd. Basic Water Cooling Tower Instruction Manual (UOP6-MKII). Vol. Issue 3. United Kingdom, July 2015.

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