Identifying regenerative furnaces: Which of the following industrial furnaces employ regenerators to store and periodically return heat to the process?

Introduction / Context:
Regeneration is a classic waste heat recovery method in heavy industry. Brickwork checker chambers alternately store heat from hot flue gases and preheat incoming combustion air or fuel, improving overall thermal efficiency.

Given Data / Assumptions:

• Typical vintage and modern designs of open hearth and by-product coke oven heating systems.
• Alternating flow through checkers on timed cycles.

Concept / Approach:
In both open hearth furnaces and coke oven heating chambers, regenerators with checkerwork are integral. Flow direction is reversed periodically so that the hot checker bricks preheat the next incoming cold stream, recovering sensible heat that would otherwise be lost.

Step-by-Step Solution:

Verification / Alternative check:
Process schematics show pairs of regenerator chambers with reversing valves, standard in these furnace types.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing regenerators with recuperators; regenerators reverse flow in packed checkers while recuperators use continuous heat exchange across walls.

Final Answer:
Both (a) and (b).