Which of the following employs an accessory known as 'drift eliminator' ?

ANS:B - Mechanical draft cooling tower.

A mechanical draft cooling tower is a heat transfer device used to remove heat from a process fluid (typically water) by transferring it to the atmosphere through evaporation and convective heat transfer. These cooling towers are commonly used in industrial facilities, power plants, and HVAC systems to cool water or other fluids used in various processes. Here's how a mechanical draft cooling tower works and some key features:

1. Basic Principle: The primary principle behind a mechanical draft cooling tower is to use air movement to dissipate heat from a hot process fluid. Hot water from an industrial process or power plant is circulated through pipes or heat exchangers and distributed over the fill material inside the cooling tower.
2. Air Circulation: Air is drawn through the cooling tower by mechanical means, such as fans or blowers, creating an upward airflow through the tower. As the hot water flows over the fill material, a portion of it evaporates into the air, absorbing heat from the remaining water and lowering its temperature.
3. Fill Material: The fill material inside the cooling tower provides a large surface area for the exchange of heat between the water and the air. It may consist of various materials, such as plastic or wood, arranged in a way to maximize contact between the water and the air while promoting uniform distribution of water over the fill surface.
4. Drift Eliminators: To minimize water loss from the cooling tower, drift eliminators are often installed to capture and remove water droplets entrained in the exhaust air leaving the tower. Drift eliminators help improve water efficiency by reducing the amount of water lost to evaporation and carryover.
5. Water Distribution System: A water distribution system is used to evenly distribute the hot water over the fill material inside the cooling tower. This system typically consists of spray nozzles, distribution basins, and pipes to ensure uniform distribution of water and optimal heat transfer efficiency.
6. Fan System: The fan system provides the mechanical draft required to draw air through the cooling tower. Fans are sized and positioned to create the necessary airflow to achieve the desired cooling effect based on the heat load and operating conditions.
7. Drift Loss and Makeup Water: Despite the use of drift eliminators, some water loss still occurs due to evaporation and carryover. Makeup water is added to the cooling tower to compensate for this loss and maintain the desired water level in the system.

Overall, mechanical draft cooling towers are efficient and cost-effective solutions for cooling large quantities of water or other process fluids in industrial applications. They offer flexibility in design, easy scalability, and effective heat transfer capabilities, making them essential components in many industrial processes and power generation facilities.