Difficulty: Medium
Correct Answer: Involve higher initial cost
Explanation:
Introduction / Context:
High-temperature furnaces often reclaim heat from flue gases using either recuperators (continuous exchangers) or regenerators (cyclic storage and release). Understanding the engineering trade-offs between these technologies helps in choosing equipment that meets temperature, footprint, and budget constraints.
Given Data / Assumptions:
Concept / Approach:
Regenerators use large thermal masses (checkerwork) and periodic flow reversal to achieve very high preheat levels, especially at extreme furnace temperatures. This typically entails heavy structures, valves, and foundations, increasing capital cost relative to many recuperators. They are not lighter/compact, and they store a larger, not smaller, quantity of heat per cycle.
Step-by-Step Solution:
Evaluate each statement against common practice.(a) “Store smaller heat”: incorrect—regenerators store substantial heat in checker bricks.(b) “Lighter & compact”: incorrect—regenerators are generally bulkier.(c) “Higher initial cost”: generally true due to size, refractory content, and valve systems.Therefore select option (c).
Verification / Alternative check:
Design handbooks and vendor literature consistently note regenerators’ higher capital cost but excellent high-temperature performance versus recuperators, validating the choice.
Why Other Options Are Wrong:
(a) Opposite of typical behavior.(b) Opposite; regenerators are not typically compact.(d) Cannot be true because (a) and (b) are false.(e) Regenerators often achieve higher, not lower, air preheat at a given duty.
Common Pitfalls:
Confusing “continuous” with “better.” While recuperators are simpler, regenerators shine at the very high end of temperature and preheat requirements.
Final Answer:
Involve higher initial cost
Discussion & Comments