Which factor remains negligible in forced convection systems?
Show answer Hide answer
Answer: C. Grashoff number
Explanation
In forced convection systems, external pumps or fans impart high fluid velocities and momentum. This forced fluid motion completely overwhelms any natural buoyancy-driven thermal expansion effects. Consequently, the Grashof number, which measures natural convection buoyancy forces, becomes entirely negligible. Convection heat transfer is classified into forced convection, natural convection, and mixed convection regimes. The Grashof number represents the ratio of buoyancy forces to viscous forces in a fluid boundary layer. Reynolds number governs forced flow behavior, while Grashof governs natural thermal buoyancy-driven flows.
Forced convection calculations in industrial heat exchangers ignore natural convection terms to simplify models. Cooling electronic components with fans relies purely on forced convection aerodynamics. Neglecting the Grashof number speeds up computational fluid dynamics simulations in forced flow equipment. Reynolds number is fundamental in forced convection for determining flow regime and friction factors. Prandtl number remains essential because it relates fluid momentum diffusivity to thermal diffusivity. The correct answer specifically targets natural convection, making the none of these choice incorrect.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. What happens to radiation heat transfer when the distance between the heat emitter and the absorbing object increases?
Show answer Hide answer
Answer: A. Decreases
Radiation heat transfer flux between separated surfaces drops as distance increases due to geometric view factor spreading. Electromagnetic radiation waves diverge as they travel away from an emitting source into open sp...
Q2. How does the thermal conductivity of a gas change with an increase in temperature___________________?
Show answer Hide answer
Answer: A. Increases
The thermal conductivity of gases increases with temperature due to higher molecular root-mean-square speeds. Faster-moving gas molecules transport thermal energy more rapidly across microscopic mean free path distances....
Q3. When is Henry’s law closely followed by a gas under conditions where its _____________ is extremely high?
Show answer Hide answer
Answer: D. None of these
Henry's law applies strictly to dilute solutions where gas molecules interact minimally with the solvent. At extremely high pressures or solubilities, non-ideal solution behavior causes severe deviations from linearity....
Q4. Elevated levels of nitrogen dioxide in the atmosphere can lead to___________________?
Show answer Hide answer
Answer: B. Bronchitis
Nitrogen dioxide is a reactive pollutant gas that penetrates deep into human lung tissue upon inhalation. This chemical irritation causes inflammation of the bronchial tubes and impairs normal respiratory function. Chron...
Q5. How does the total emissivity of metallic conductors vary with rising temperature____________________?
Show answer Hide answer
Answer: A. Increases
As metallic conductors increase in temperature, their atomic lattice vibrations alter surface emission properties. This thermal excitation enhances the overall emissivity of metallic conductors across infrared radiation...
Q6. Hot extrusion processes are unsuitable for the production of____________________?
Show answer Hide answer
Answer: A. Cast iron pipe for domestic water supply
Hot extrusion requires high ductility and plastic flow under compressive stress at elevated temperatures. Cast iron contains high carbon and graphite flakes, making it inherently brittle with virtually zero hot-working d...