Heat Transfer in Boiler Furnace

In a boiler furnace, heat is mainly transferred by conduction, convection, and radiation. Let's understand how each of these methods plays a role in heat transfer in a boiler furnace.

1. Conduction:
Conduction is the transfer of heat through direct contact between particles or objects. In a boiler furnace, conduction occurs primarily within the solid materials that make up the furnace structure. The heat generated by the combustion of fuel is conducted through the walls of the furnace to the surrounding water or steam. This transfer of heat helps in raising the temperature of the water or steam.

2. Convection:
Convection is the transfer of heat through the movement of fluids (liquids or gases). In a boiler furnace, convection plays a crucial role in transferring heat from the combustion gases to the water or steam. As the hot gases rise, they come in contact with the tubes or surfaces carrying the water or steam. This contact leads to the transfer of heat from the hot gases to the fluid, resulting in an increase in its temperature.

3. Radiation:
Radiation is the transfer of heat through electromagnetic waves. In a boiler furnace, radiation occurs when the hot combustion gases emit thermal radiation. This radiation travels in the form of electromagnetic waves and can directly heat the surrounding surfaces (such as boiler tubes) without the need for physical contact. The heated surfaces then transfer the heat to the water or steam through conduction and convection.

Explanation of Correct Answer (Option C): Boiler Furnace

The correct answer to the given question is option C, which is the boiler furnace. This is because a boiler furnace involves all three modes of heat transfer - conduction, convection, and radiation. In a boiler furnace, the heat generated by the combustion of fuel is conducted through the furnace walls, convected to the water or steam through the movement of hot gases, and radiated to the surrounding surfaces and fluid.

Heat Transfer in Other Options:

a) Insulated pipes carrying hot water:
In insulated pipes carrying hot water, heat transfer primarily occurs through conduction. The insulation helps in minimizing heat loss through convection and radiation.

b) Refrigerator freezer coil:
In a refrigerator freezer coil, heat transfer mainly occurs through convection. The cold refrigerant absorbs heat from the surrounding air through convection, causing the air to cool down.

d) Condensation of steam in a condenser:
In the condensation of steam in a condenser, heat transfer occurs through conduction and convection. The hot steam comes in contact with the condenser tubes, and heat is transferred through conduction. The cooling medium (usually water) flowing through the tubes absorbs the heat through convection, causing the steam to condense.

Overall, while conduction, convection, and radiation play important roles in various heat transfer processes, the boiler furnace involves all three modes of heat transfer to efficiently transfer heat from the combustion gases to the water or steam.