An industrial furnace utilizes a tall vertical exhaust stack to naturally vent out combustion gases without the use of mechanical fans. Arrange the following stages of this natural convection cycle in the correct chronological order, beginning immediately after the fuel is ignited.
- 1Combustion transfers thermal energy to the surrounding gases, increasing their molecular kinetic energy.
- 2The heated gases expand and increase in volume, which proportionally reduces their overall density.
- 3The lower-density gases experience a buoyant force and rise rapidly up the vertical exhaust stack.
- 4The upward movement of the hot gases creates a low-pressure zone at the base, drawing in cooler, denser ambient air.
Answer
The sequence begins with the transfer of thermal energy (heating), followed by volumetric expansion (density reduction), leading to upward movement (buoyancy), and concluding with cooler air being drawn in to replace the rising gases (draft creation).
Natural convection is entirely dependent on density differences. Thermal energy must first be applied to the fluid, causing it to expand. This volumetric expansion lowers the fluid's density, creating a buoyant force relative to the surrounding cooler fluid. The buoyant hot fluid rises, and its departure creates a localized pressure drop at the bottom, which pulls in cooler, denser fluid to continue the cycle.
Step-by-Step Solution
Key Concept
Density-Driven Natural Convection (The Stack Effect)