Natural Draft Cooling Towers: Design, Components, and Functioning, Study notes of Thermodynamics

Download Natural Draft Cooling Towers: Design, Components, and Functioning and more Study notes Thermodynamics in PDF only on Docsity! Natural draft cooling towers operate on the stack effect which causes the hot air in the tower to rise (natural draft). Wet natural draft cooling towers are used mainly for electrical energy industry, but can be used for other industrial objects. Such towers allow the cooling of high water volumes and are designed both from concrete and metal structures. 1. Natural Draft Cooling Towers By: Nicholas Berkholz ENG 3060 Section 003 2. 2. What is a Natural Draft Cooling Tower • What is a • A natural draft cooling tower is a means to remove waste Natural Draft heat from a system and release it into the atmosphere. Cooling • Typically used at oil refineries, chemical plants and power Tower? plants to remove heat absorbed from circulating cool water • A Few systems. Important • A common shape is the hyperboloid (See Fig. 1) Terms • Cooling towers have been around for over 100 years. • Components However, in their early for were only about 20 meters high. • How it Works Today, some can reach over 200 meters. • Remarks • “As recently as 20 years ago, cooling towers were more the exception than the rule in the industry because of their severely high operating cost and the large amount of capital required for construction. But with today's need for water conservation and minimal environmental impact. industry is turning more and more to recycling water.”(GC3) 3. 3. Fig. 1 4. 4. Important Terms • Wht is aa What is • Wet Bulb Air Temperature - the temperature a volume of Natural Draft Natural Draft air would have if cooled adiabatically to saturation at Cooling Cooling constant pressure by evaporation of water into it, all latent Tower? heat being supplied by the volume of air(Wiki 1). Also Tower? • A Few known as the dew point of ambient air. • A Few Important • Adiabatically - in meteorology, referred to also as adiabatic Important Terms cooling: when air cools or heats as it expands or contracts • Terms Components with pressure change without losing or gaining heat energy • • Components How it Works by radiation or to its surroundings. (Wiki 2) • How it Works • Dry Bulb Air Temperature – The temperature at which a thermometer reads freely in air but is shielded from • Remarks radiation and moisture. • Natural Draft or Stack Effect – When there is a large pressure differential between the outside air and air within a structure. Warm, moist air is less dense than dry air of the same pressure thus causing the warm, moist air to rise. 5. 5. Components • • What isis a What a Natural • Supply Basin Draft Cooling Natural Draft • Tower Pumps Tower? • Cooling Towers • Cooling A Few Important – Vertical Ribs Tower? Terms – Reinforced Concrete Shell • • Components A Few – Internal Void • How it Works – Diagonal Columns Important • Remarks Terms • Hot Water Inlet • Components • Fill – Splash • How it Works – Film • Remarks • Hot Water Distribution System • Cold Water Collection • Drift Eliminators - Drift is water lost from cooling towers as liquid droplets are entrained in the exhaust air. The drift loss is independent of the water lost by evaporation. The drift loss may be expressed in units of lb/hr or percentage of circulating water flow. Drift eliminators are used to control this drift loss from the tower. (Mist) 6. 6. Components • What is a Natural Draft Cooling Tower? • A Few Important Terms • Components • How it Works • Remarks 7. 7. How it Works • What is a Natural Draft • Step 1 - As hot water enters the natural draft cooling Cooling towers, through a series of pumps, to the warm water inlet Tower? • A Few Important Terms • Components • How it Works • Remarks 8. 8. How it Works • What is a Natural Draft • Step 2 - The warm water is then distributed into through a Cooling packing or fill material inside the tower keeps the water Tower? evenly distributed. This is plays a major role and contributes • A Few heavily to the efficiency of the tower. Important – (i.e. better the distribution allows for more contact time, and greater Terms surface area, which allows for more heat removal) • Components • How it Works • Remarks 9. 9. How it Works • What is a Natural Draft • Step 3 - As the water is being distributed, the exposed Cooling lower portion of the tower allows for air to pass over the Tower? cold water basin. It’s this passing of the ambient air over • A Few the cold water basin which actually creates the differential, Important thus cause the natural draft or “Stack Effect.” Terms • Components • How it Works • Remarks 10. 10. How it Works • What is a Natural Draft • Step 4 - As this differential is being produced the shape of Cooling the tower itself, the hyperbolic shape, induces current Tower? upwards. • A Few Important Terms • Components • How it Works • Remarks 11. 11. Remarks • What is a • This system is over all extremely efficient and typically Natural Draft requires no fans or mechanical means to cool the water. Cooling • Very common practice now due to the structures strength Tower? and minimum required materials to construct. • A Few • Efficiency of the tower depends on the ambient Important temperature. Terms • Components • How it Works • Remarks . How it Works How it Works Step 2- The warm water is then distributed into through a packing or fill material inside the tower keeps the water evenly distributed. This is plays a major role and contributes heavily to the efficiency of the tower. = (le. betterthe distribution allows for more contact time, and greater surface area, Which allows for more heat remova1) è How it Works How it Works Step 3- Asthe water is being distributed, the exposed lower portion of the tower allows for airto pass over the cold water basin. It's this passing of the ambient air over the cold water basin which actually creates the differential, thus cause the natural draft or "Stack Effect.”  How it Works Step 4 - Asthis differential is being produced the shape of the tower itself, the hyperbolit shape, induces current upwards * Howit Works Remarks This system is over all extremely efficient and typically requires no fans or mechanical means to cool the water. Very common practice now due to the structures strength and minimum required materials.to construct. * Efficiencvofthe tower depends on the ambient temperature. *. Remarks