Abstract:
Cooled water is necessary for air conditioners, manufacturing processes, power
generation and many other purposes. Cooling tower is an equipment used to reduce the
temperature of water by extracting heat from water and emitting it to the atmosphere. Cooling
towers are able to lower the water temperatures more than other devices that use only air to reject
heat, like the radiator in a car and are therefore more cost-effective and energy efficient. In the
past most of the processes requiring cooling used piped town water through the equipment. After
cooling the equipment the water was drained to the gutter. So, the water was totally wasted after
using it once. Cooling towers were introduced so that the wastage of water can be reduced by
recycling the water. Cooling towers make use of evaporation. Some of the water is evaporated
into a moving air stream and subsequently discharged into the atmosphere. The evaporation
process only takes place on the surface of a liquid and needs latent heat of vaporization to
happen. Sensible heat is drawn from the body of the water to the surface to supply the energy
needed for the latent heat. It can be seen that for a little evaporation a lot of sensible heat will be
needed therefore the main body of the circulating water is cooled for very little loss of water.
The main purpose of this study is to work on developing mathematical model for cooling
tower and examine methodically the performance of a model of closed loop 10 RT counter flow
induced draft bottle type cooling tower which has been developed only for this project purpose.
A detailed mathematical model for a counter flow induced draft cooling tower has been
developed using Merkel Theory. Dr. Merkel developed a cooling tower theory for the mass and
sensible heat transfer between the air and water in counter flow cooling tower. Several
experiments has been conducted by changing the L/G (L= water flow rate; G= air mass flow
rate) ratio with the help of changing the flow rate (L) of water to observe the behavior of
different characteristics, represented in graphical form. Tower characteristics graph has been
plotted at 90%, 100% and 110% water flow rate. The performance prediction of cooling tower
related with the performance curves by means of the simple method is made by a few design
parameters as well as water flow rate, L/G, KaV/L (Tower Demand), range, cold water
temperature, wet bulb temperature, and fan BHP. The performance prediction by the detail
method is requiring all the actual cooling tower dimensions, thermal rating conditions, and all the
mechanical rating conditions. Calculation of pump selection for the circuit has been shown.
The efficiency obtained from the experiment we have conducted varies from 35% to 45%
which indicates the good performance of the system we have developed.
