Understanding Boiler Types: Fire-Tube vs. Water-Tube

A boiler is a closed vessel in which fluid (usually water) is heated. The fluid is then used to create steam, which is typically used for power generation or heating purposes. Boilers are generally classified into two main types based on how the heat is transferred to the water:

• Fire-Tube Boilers: In this type, hot combustion gases pass through tubes that are surrounded by water. The heat from the gases is transferred through the tube walls to the water, turning it into steam. These boilers are typically used for lower pressure and smaller capacities.
• Water-Tube Boilers: In this type, water flows through tubes, and the hot combustion gases flow around these tubes. Heat is transferred from the hot gases to the water inside the tubes. These boilers are generally used for higher pressure and larger capacities.

Analyzing the Given Boiler Options

Let's look at each option provided and determine its type:

• Stirling boiler: This is a type of water-tube boiler. It features multiple drums and bent tubes, designed for high capacity and efficiency.
• Babcock and Wilcox boiler: This is also a well-known type of water-tube boiler. It is characterized by having inclined water tubes connected to headers and drums.
• Yarrow boiler: This boiler is primarily used in marine applications and is a type of water-tube boiler. It features multiple banks of tubes connecting drums.
• Cochran boiler: This is a vertical, multi-tubular fire-tube boiler. The hot gases from the furnace pass through horizontal tubes that are surrounded by water in a cylindrical shell. This design is compact and often used for relatively small capacities.

Identifying the Fire-Tube Boiler

Based on the classifications, the Cochran boiler is the type of boiler among the options provided where the hot gases flow through tubes surrounded by water, which is the defining characteristic of a fire-tube boiler.