The relative importance of viscous heating compared to conductive heat transfer driven by temperature gradients is gauged by the _______________ number?
Show answer Hide answer
Answer: D. Brinkman
Explanation
The Brinkman number quantifies the relative importance of viscous heat generation inside a flowing fluid. It compares viscous dissipation heating to heat transfer driven by external temperature gradients. High Brinkman numbers indicate that internal friction significantly elevates the fluid temperature. Viscous dissipation occurs when mechanical energy converts into thermal energy through fluid friction. Dimensionless numbers help engineers determine which physical transport mechanisms dominate a system. The Brinkman number incorporates dynamic viscosity, velocity, thermal conductivity, and temperature difference.
Polymer processing and extrusion industries monitor viscous heating to prevent thermal degradation of melts. High speed lubrication systems evaluate viscous dissipation to avoid bearing overheating failures. Microfluidic devices handling viscous liquids must account for internal frictional heating effects. The Grashoff number evaluates buoyancy driven natural convection relative to viscous forces. The Stanton number relates heat transfer to fluid mass flow and heat capacity. Condensation numbers characterize film condensation heat transfer coefficients on vertical surfaces.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. A 0.1 m radius metal sphere at a uniform 90°C is exposed to air at 30°C. Given metal density 3000 kg/m3, specific heat 0.4 kJ/kg.K, and heat transfer coefficient 50 W/m2.K (ignoring internal gradients), the cooling time to 60°C in hours is_________________?
Show answer Hide answer
Answer: D. 0.15
The lumped capacitance method assumes negligible internal thermal resistance throughout the metal sphere. Applying the transient energy balance yields an exponential temperature decay equation involving convective terms....
Q2. When the natural logarithm of the temperature difference between a hot liquid and its room environment is plotted against time, the resulting curve is approximately a/an___________________?
Show answer Hide answer
Answer: B. Straight line
Lumped system cooling follows a first order exponential decay equation for temperature differences. Taking the natural logarithm of an exponential function yields a linear equation with a constant slope. The resulting st...
Q3. The ____________ chart is designated as the transient heat conduction chart?
Show answer Hide answer
Answer: A. Dirhing’s
Heisler charts provide graphical solutions for transient heat conduction in multi dimensional geometries. These charts plot dimensionless centerline temperature against Fourier number for various Biot numbers. Engineers...
Q4. A perfect black body acts as an ideal _____________ of radiation?
Show answer Hide answer
Answer: C. Both A. & B.
A perfect black body absorbs all incident thermal radiation without reflecting or transmitting any. It simultaneously emits the maximum possible thermal radiation for any given temperature and wavelength. This theoretica...
Q5. A sphere of radius ‘R1’ is contained within a concentric sphere of radius ‘R2’. The view factor for radiation from the outer sphere to the inner sphere is ________________?
Show answer Hide answer
Answer: B. R2/(R1+R2)
Using radiation view factor algebra for concentric spheres, the view factor from the outer sphere to the inner sphere is given by R2/(R1+R2).
Q6. A diathermanous medium _______________ thermal radiation entirely?
Show answer Hide answer
Answer: C. Transmits
A diathermanous medium allows thermal radiation to pass through without absorbing or reflecting it. Such substances are completely transparent to infrared and visible electromagnetic radiation waves. Radiation passes acr...