Where are regenerators commonly installed? Select the furnace applications that routinely include checkerwork regenerators for high-efficiency combustion air preheating.

Introduction / Context:
Regeneration with checker brick structures is prominent wherever very hot flue gases are available and high preheat of combustion air or fuel delivers large fuel savings. Three iconic applications are glass melting tanks, open hearth steel furnaces, and by-product coke ovens.

Given Data / Assumptions:

• High-temperature continuous firing with substantial waste heat potential.
• Periodic flow reversal to alternate between storage and release phases.

Concept / Approach:
Regenerators capture sensible heat from exhaust and return it via preheated air/fuel during the next cycle. All three listed furnace types utilize checker chambers because the thermal duty and temperature levels justify the added complexity and capital cost.

Step-by-Step Solution:

Verification / Alternative check:
Process flow diagrams and historical furnace literature consistently depict dual regenerator chambers with reversing valves.

Why Other Options Are Wrong:

Common Pitfalls:
Interchanging regenerators with recuperators; remember regenerators require periodic flow reversal and storage mass.

Final Answer:
all (a), (b) and (c).