How does the relative heat absorption vary across successive equal areas of boiler convection heating surfaces____________________?
Show answer Hide answer
Answer: B. decreases
Explanation
As flue gases pass over successive convection heating surfaces, they transfer thermal energy. This continuous heat transfer causes the temperature of the flue gases to drop steadily. Lower gas temperatures reduce the temperature difference, decreasing heat absorption per unit area. Convection heat transfer depends directly on the temperature difference between fluids. Boiler convection sections include economizers and superheaters arranged in series. Gas temperature decreases along the flow path as heat is absorbed by boiler water.
Boiler designers arrange heating surfaces counter-flow to maximize average temperature differences. Understanding heat absorption gradients helps optimize surface area sizing in utility boilers. Inefficient heat transfer in later passes leads to higher stack gas energy losses. Heat absorption does not increase because the driving temperature difference diminishes. Remaining unaffected violates basic thermodynamic principles of convective heat transfer. Complex fluctuations do not occur; heat absorption drops steadily along the gas path.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. What is the zone bounded by the separation streamline and a solid body's outer surface called__________________?
Show answer Hide answer
Answer: A. wake
The region of recirculating flow immediately downstream of a moving body bounded by separation streamlines is known as the wake. Flow separation occurs when adverse pressure gradients force boundary layers to detach from...
Q2. What typical percentage distribution represents useful power versus exhaust, cooling, and friction losses in diesel engines____________________?
Show answer Hide answer
Answer: E. 25:5:35:35
Diesel engines convert roughly twenty five percent of fuel energy into useful mechanical power output. Thermal rejection through cooling jackets and exhaust gases accounts for seventy percent of total energy. Frictional...
Q3. How is the crown radius of a dished pressure vessel head typically estimated______________________?
Show answer Hide answer
Answer: C. one
Dished pressure vessel heads are manufactured in various geometries, including torispherical and ellipsoidal dished configurations. Standard design codes specify that the crown radius of a dished head should equal the in...
Q4. Under what condition will the normal stress at a point in a fluid remain uniform in all directions__________________________?
Show answer Hide answer
Answer: E. it is at rest
When a fluid is at rest, shear stresses are zero, meaning the normal stress is isotropic and uniform in all directions. Stationary fluid molecules do not experience relative sliding motion, eliminating directional fricti...
Q5. How do tube diameters in natural circulation boilers compare to those in controlled circulation units___________________?
Show answer Hide answer
Answer: A. more
Natural circulation relies entirely on density differences between heated and cooled fluid columns. Larger diameter tubes provide reduced flow resistance to maintain adequate thermosiphon circulation rates. Forced circul...
Q6. What is the most frequently used firing order in four-cylinder inline internal combustion engines__________________?
Show answer Hide answer
Answer: B. 1-3-2-4
Four-cylinder inline internal combustion engines require a carefully selected firing order to maintain smooth rotational balance. The sequence 1-3-2-4 distributes power strokes evenly across the 720-degree combustion cyc...