As operating pressure rises in water tube boilers, natural convective water circulation rate_________________?
Show answer Hide answer
Answer: B. decreases
Explanation
Natural convective water circulation in boilers relies on density differences between liquid water and steam bubbles. As operating pressure increases, steam density rises while liquid water density decreases toward saturation values. This diminishing density difference reduces the buoyancy force driving natural water circulation, slowing the rate. Water-tube boilers generate steam inside heated tubes, creating natural thermo-syphon circulation loops. Buoyancy drives circulation as lighter steam-water mixtures rise while denser cooler water descends downcomers. High operating pressures compress steam, increasing its density and reducing the thermal buoyancy driving force.
High-pressure utility power boilers often abandon natural circulation in favor of forced-circulation pumps. Boiler designers must evaluate circulation reliability to prevent tube overheating and burnout at elevated pressures. Understanding thermal convection principles ensures safe and efficient steam generation in industrial plants. Stating that circulation rate increases contradicts thermodynamic laws governing density changes at high pressures. Claiming circulation remains unaffected ignores the direct impact of reduced density differences on buoyancy. Suggesting circulation fluctuates unpredictably overlooks the well-established thermodynamic laws of boiler fluid dynamics.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. Identify the technique that does NOT serve as a valid method for raising the fatigue limit_______________?
Show answer Hide answer
Answer: C. surface decarburisation
Surface decarburisation depletes carbon from the outer metal layer, reducing hardness and strength. Lower surface carbon creates weak microstructural zones that readily initiate fatigue cracks. Since it degrades fatigue...
Q2. The included notch angle machined on a standard Izod impact test specimen measures________________?
Show answer Hide answer
Answer: D. 45°
The standard Izod impact test specimen is machined with a 45-degree included notch angle. This precise notch geometry creates a severe triaxial stress state and localized stress concentration during impact testing. Stand...
Q3. Monel metal is a specialized alloy consisting of_________________?
Show answer Hide answer
Answer: A. 63 to 67% nickel and 30% copper
Monel metal is a specialized corrosion-resistant alloy composed mainly of nickel and copper. It typically contains roughly sixty-three to sixty-seven percent nickel and about thirty percent copper. This specific chemical...
Q4. Non-uniform fluid flow conditions arise when_________________?
Show answer Hide answer
Answer: E. velocity, depth, pressure, etc. change from point to point in the fluid flow
Non-uniform fluid flow occurs when flow properties vary spatially along the fluid path. Velocity depth and pressure change from point to point within the flowing fluid system. This spatial variation distinguishes non-uni...
Q5. What type of engine governing system is standard for spark-ignition petrol engines________________?
Show answer Hide answer
Answer: A. quantity governing
Spark-ignition petrol engines control output power primarily by throttling the incoming air-fuel mixture. Quantity governing varies the mass quantity of the charge entering the cylinders while keeping fuel ratio constant...
Q6. Newton's law of viscosity establishes a direct mathematical correlation between____________________?
Show answer Hide answer
Answer: A. shear stress anctthejiate of angular distortion
Newton's law of viscosity states that shear stress is directly proportional to the velocity gradient in a fluid. The rate of angular distortion in fluid flow is mathematically equivalent to the spatial gradient of fluid...