Cooling Tower Demonstration System

Cooling Tower Demonstration System

Figure 1: Cooling Tower Demonstration System

No	Component
1	Orifice
2	Water Distributor
3	Temperature Indicator
4	Make-up tank
5	Heater
6	Inclined Manometer
7	Valves
8	Receiver Tank
9	Blower
10	Temperature Sensor

INTRODUCTION AND THEORY:

Cooling tower function is used to cool down hot water by removing the heat. The heat of the water is mainly removed by evaporation process. Besides that, water also cooled down by radiation, conduction, convection. However, the effect of cooling is not significant compared to evaporation.

Figure 2: Schematic Diagram of Mass flow for cooling Tower

Cooling tower is widely used in industry and it main function is removing excessive unwanted heat from high temperature water. Heat from hot water is removed by evaporation process. However, water also cooled down by radiation, conduction, convection. However, the effect of cooling is not significant compared to evaporation.           

In the evaporation process, small portion of water was evaporated, thus the exiting air has higher humidity ratio and the water leave the tower in the form of vapour. With the assumption of the dry air and water vapour are ideal gasses, the mass of water evaporated can be determined. The mass of water evaporated should be equal to mass of water losses in make-up tank.

There are a few applications that are similar to the cooling tower demonstration system such as closed-cycle wet cooling tower, closed-cycle dry cooling tower and open-cycle cooling tower. In a closed-cycle wet cooling system, the heat from the turbine is absorbed by a small portion of water, some of the water released from the cooling tower as vapour and the rest being resaved and recirculated in next cycle. The wet cooling system consumes approximately 97% less water than the one-pass cooling system. This reduction in the amount of water greatly reduces the number of organisms that have been killed during ingestion.

Closed-loop circulating dry cooling tower is another alternative that uses much less water than once through cooling, with less environmental impact. In areas with scarce water resources, the dry cooling system more common used because the dry cooling system required less water and it has high energy efficiency. This system use a small amount of water and water can be resaved and recirculated in next cycle. Therefore, the dry cooling system solves the problem for continuous access to cooling water and does not produce the same air quality problems as the closed-cycle wet system. The dry cooling system also significantly reduces the volume of water discharged into the environment, but the concentrated wastewater may contain high levels of contaminants, which causes toxic problems. In addition, the dry cooling system has a high capital cost and is generally less efficient than a wet cooling system.

Open-cycle cooling tower is removing heat from water because of the material and heat exchange between the water and the ambient air. Warm water is pumped from the load tank through the control valve and water flow meter to the column cap. After water enters the tank, it is uniformly distributed over the top packing deck and spreads over the plates. At the same time a large thin film of water is exposed to the air stream. Then, the water is quickly cascades down the column and leaves at the bottom. Through this process the heat exchange process is occurred where water is cooled. However, the water cannot be cooled down below the wet bulb temperature.

Packing Density has linear relationship to efficiency of cooling tower. Packing Density is the ratio of the surface areas of all levels of the cooling column to the column volume in the units of m2 /m3. As the packing density of the distributor of cooling tower increased, the surface area of plates that are exposed to water increased. Total surface area and packing density of the distributor of cooling tower can be increased by increasing the number of plates. The efficiency of cooling tower efficiency increased as the total surface area in distributor increased. This is due to higher evaporation rate as more water contact with plates. Thus, more heats are removed. Furthermore, the design for arrangement of plates is important because good design helps the water flow smoothly and the heat can be released to environment without being trapped.