Experimental Study of a Forced Draft Cross Flow Cooling Tower-Effect of Air Velocity

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ACKNOWLEDGEMENT

I am gratefully indebted to my honorable supervisor Dr. Bodius Salam Associate Professor, Department of Mechanical Engineering, CUET, Bangladesh for his sincere guidance, supervision, valuable suggestions and kind cooperation. I also would like to give cordial thanks to workshop, heat engine laboratory, heat transfer laboratory in charges for helping me for the project about cooling tower. The Author also pays his profound honor to his parents, close relatives, and friends for their inspiration towards the completion of this work Above all, I am always grateful to almighty Allah, the most merciful and beneficent.

Author Shehabur Rahman Khan August, 2009

ABSTRACT
This paper presents an experimental work, which studies the performance of a forced draft cross flow type wet cooling tower. Normally, cooling tower’s main function is to cool heated circulating by exposing it to air. The cooled water is then circulated through the system by circulating water pumps. This research work was to study the effect of air velocity on performance of wet cooling tower that fabricated by Rashidul Hasan (2008). During the experimentation the air velocity was varied in the range 3.1-1.4 m/s with keeping water flow rate constant at 7.5 lit/min and water inlet temperature constant at 55 °C. From this study, it was found that the range, thermal effectiveness, and cooling capacity are increased with increase of air velocity and approach was decreased. This result was very good for a cooling tower. But at the same time it was found that evaporation loss also increase with increase of air velocity. The results are graphically represented with respect to air velocity and necessary explanation of result is also given.

LIST OF FIGURES
Figure No.Figure Name Page No.
Fig. 1.1 Schematic overview of a generic cooling tower flow 1 Fig.1.2 Natural draft cooling tower 4
Fig. 1.3 Induced and forced draft cooling tower5
Fig. 1.4 Induced and forced draft cooling tower6
Fig. 1.5Cross flow cooling tower7
Fig. 1.6 Double flow cooling tower7
Fig. 1.7 Single flow cooling tower8
Fig. 1.8 Counter flow cooling tower8
Fig. 2.1 Water drop with inter facial film12
Fig. 2.2 Graphical representation of tower characteristics14 Fig. 2.3 Graph of Adjusted Hot Water Temperatures15
Fig. 2.4 Representation of the general humidification process16 Fig. 2.5 Cooling tower thermal efficiency21
Fig. 2.6 Cooling tower performance21
Fig. 2.7 Wind velocity and inlet air temperature (wet-bulb)22 Fig. 3.1 Water reservoir38
Fig. 3.2 Rotameter and pump used for cooling tower39
Fig. 3.3 Axial fan used 40
Fig. 3.4 Fill with distribution system40
Fig. 3.5Complete view of fabricated wet cooing tower41
Fig. 3.6 Schematic diagram of the wet cooling tower42
Fig. 5.1 Effect of air velocity on cooling tower range46 Fig. 5.2 Effect of air velocity on cooling tower approach47 Fig. 5.3 Effect of air velocity on cooling tower effectiveness47 Fig. 5.4 Effect of air velocity on cooling tower cooling capacity48 Fig. 5.5 Effect of air velocity on Evaporation loss (%)48 Fig. 5.6Air velocity Vs outlet air relative humidity49

CONTENTS
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