Furnace heat recovery comparison For the same heat-recovery duty, how do regenerators compare with recuperators in terms of size, cost, and space requirements in industrial furnace service?

Introduction / Context:
Industrial furnaces often recover waste-heat from hot flue gases using either recuperators (continuous heat exchange across a wall) or regenerators (cyclic heat storage in a refractory checkerwork). For the same heat-recovery duty, designers must understand practical differences in bulk, cost, and operation to select the appropriate device.

Given Data / Assumptions:

• “Same duty” means similar average heat recovery from the same flue-gas stream.
• General furnace practice at steel/reheat/soaking-pit temperatures.
• Comparison centers on physical size, installed cost, and footprint.

Concept / Approach:
Recuperators transfer heat continuously through metallic or ceramic walls. Regenerators alternately store and release heat in a large mass of refractory media. Because regenerators require substantial checker volume and associated ducting/valving for periodic flow reversal, they are physically larger and take more plot space than compact recuperators designed for the same heat duty.

Step-by-Step Solution:

Verification / Alternative check:
Plant layouts show regenerator checker chambers can be building-scale structures. Recuperators (especially compact metallic types) mount near stacks/ducts with far smaller volume per unit duty.

Why Other Options Are Wrong:

• Are less costly: Typically false; extra brickwork, valves, and structure raise cost.
• Are of smaller size: Opposite of practice; regenerators are bulkier.
• All of (a), (b) and (c): Invalid because only (a) holds true.
• Have lower heat-storage inertia: Regenerators rely on storage, so inertia is higher, not lower.

Common Pitfalls:
Assuming better efficiency always means smaller equipment; with regenerators, efficiency gains often come with larger volume.

Final Answer:
Occupy more space