TOP Flashcards
If the thermal conductivity of the fluid increases, the heat transfer coefficient will
a. increase
b. remain the same
c. decrease
d. none of these
a. increase
If the viscosity of the fluid will increase, the heat transfer coefficient in a turbulent flow system will
a. increase
b. remain the same
c. decrease
d. none of these
c. decrease
In a fluid, if the currents are set in motion by the action of a mechanical device, and the flow is independent of density gradients, the phenomenon is called
a. natural convection
b. forced convection
c. thermal conduction
d. centrifugation
b. forced convection
The heat transfer radially across an insulated pipe per unit area
a. remains constant
b. is inversely proportional to the thermal conductivity
c. decreases from pipe wall to the insulated surface
d. increases from pipe wall to the insulated surface
c. decreases from pipe wall to the insulated surface
The transfer of heat from a point to another within a fluid, or between a fluid and a solid or another fluid, by the movement or mixing of the fluids involves
a. conduction
b. radiation
c. convection
d. none of these
c. convection
It is a method of developing the design for a heat exchanger wherein the engineer assures the existence of an exchanger and makes calculations to determine if the exchanger would handle the process requirements under reasonable conditions.
a. heat exchanger modelling
b. heat exchanger calculation
c. rating a heat exchanger
d. evaluation of heat exchanger performance
c. rating a heat exchanger
When water inside a beaker is being heated over a hot plate, the mechanism of heat transfer through the water is considered to be
a. conduction
b. forced convection
c. natural convection
d. radiation
c. natural convection
The driving force in heat transfer is
a. concentration gradient
b. temperature gradient
c. viscosity gradient
d. thickness of the solid in question
b. temperature gradient
In using the design equation of heat transfer, q = UAΔTln, the U and A may either based on the inside or outside area of the pipe. For a system where air is flowing inside a pipe while being heated by condensing steam outside the pipe, the proper U and A to be used is
a. based on the inside area
b. based on the outside area
c. it does not matter
d. non of these
a. based on the inside area
If a man touches two metals which were kept together at room temperature, why would one metal feel colder than the other?
a. one has a high heat transfer coefficient
b. one has a high thermal conductivity
c. one has a lower temperature
d. one has a higher heat capacity
b. one has a high thermal conductivity
The term hD/k is known as
a. Prandtl Number
b. Peclet Number
c. Nusselt Number
d. Reynold’s Number
c. Nusselt Number
In heat transfer by conduction, due to symmetry the heat flow at a point is perpendicular to the isothermal surface through the point. This mode of conduction is characteristic of
a. non-isotropic solids
b. isotropic solids
c. insulators
d. conductors
b. isotropic solids
The ratio of the internal thermal resistance of a solid to the boundary layer thermal resistance is described by
a. Nusselt Number
b. Prandtl Number
c. Biot Number
d. Reynolds Number
c. Biot Number
The measure of the relative effectiveness of momentum and energy transport by diffusion in the velocity and thermal boundary layers is given by
a. Nusselt Number
b. Prandtl Number
c. Biot Number
d. Reynolds Number
b. Prandtl Number
The property of the solid that provides a measure of the rate of heat transfer relative to the energy storage is referred to as
a. thermal conductivity
b. heat capacity
c. thermal diffusivity
d. viscosity
c. thermal diffusivity
The range of wavelengths of electromagnetic waves that is associated with thermal radiation is from
a. 10^-5 to 10^-2 µm
b. 0.1 to 100 µm
c. 100 to 10000 µm
d. none of these
b. 0.1 to 100 µm
An ideal surface that absorbs all incident radiation, regardless of wavelength and direction and is also considered to be a perfect emitter is referred to as a
a. gray body
b. black hole
c. black body
d. pin hole
c. black body
The spectral distribution of a perfect emitter has a maximum and that the corresponding wavelength depends on temperature. The maximum spectral emissive power is displaced to shorter wavelengths with increasing temperature. These statements refer to
a. Stefan-Boltzman Law
b. Kirchoff’s Law
c. Wien’s Law
d. Planck’s Law
C. Wien’s Law
The amount of radiation emitted in all directions and over all wavelengths by a perfect emitter is proportional to the fourth power of the absolute temperature of the emitter. This is the statement of
a. Stefan-Boltzman Law
b. Kirchoff’s Law
c. Wien’s Law
d. Planck’s Law
a. Stefan-Boltzman Law
The ratio of the emissive power of a body to its absorptivity is a constant and the same for all radiating bodies in a confined enclosure under thermal equilibrium. This is a statement of
a. Stefan-Boltzman Law
b. Kirchoff’s Law
c. Wien’s Law
d. Planck’s Law
b. Kirchoff’s Law
A theoretical body where the absorptivity and emissivity are independent of the wavelength over the spectral region of the irradiation and the surface emission is called
a. black body
b. gray body
c. opaque body
d. transparent body
b. gray body
Thermal lumped analysis may be applied if
a. the thermal conductivity of the solid is very small b. the convective resistance is very large
c. the convective resistance is very small compared with the conductive resistance
d. the conductive resistance is very small compared with the convective resistance
d. the conductive resistance is very small compared with the convective resistance
Two parallel infinite walls at different temperatures are radiating energy to each other. If a sheet of negligible thermal resistance is placed midway between the walls, and the sheet is considered a black body, the heat transferred by radiation between the two walls is
a. maintained the same
b. decreases
c. increases
d. can not be determined
b. decreases
Which among the gases listed is transparent to gas radiation
a. oxygen
b. carbon dioxide
c. water vapor
d. ammonia
a. oxygen
In boiling, the stage when the rate of bubble formation increases so that the velocity of circulation increases and the heat flux, q and ΔT also increase is referred to as
a. transition boiling
b. nucleate boiling
c. film boiling
d. rapid boiling
b. nucleate boiling
A semi-infinite solid in heat conduction is one where
a. only the conduction on one side affects the temperature distribution
b. the thickness is not so large
c. the length is semi-infinite
d. the heat flow on the surface is negligible
a. only the conduction on one side affects the temperature distribution
A 2-4 shell and tube heat exchanger means that there are
a. 2 tube passes and 4 shell passes
b. 2 baffles and 4 tubes
c. 2 shell passes and 4 tube passes
d. 2 baffles and 4 shells
b. 2 baffles and 4 tubes
Air flowing inside the annular space of a double pipe heat exchanger is being heated by steam inside the inner pipe. For this case, the U in the heat transfer equation should be based on
a. the outside area of the inner pipe
b. inside area of the outer pipe
c. inside area of the inner pipe
d. it does not matter
a. the outside area of the inner pipe
When the pressure of the evaporator chamber is decreased, the boiling point of the solution inside the chamber will
a. increase
b. remain the same
c. decrease
d. none of these
c. decrease
The concentration of glycerine from a water solution by the application of heat is
a. distillation
b. evaporation
c. crystallization
d. reverse osmosis
b. evaporation
Which of the two evaporator flow configurations needs fluid motive devices to transfer solution from one effect to the other effect?
a. feedforward
b. backward flow
b. backward flow
A heat transfer device that is normally used to liquefy vapors is
a. evaporator
b. condenser
c. reboiler
d. none of these
b. condenser
In a country where capital is scarce and energy cost is low, which is appropriate to install?
a. multiple effect evaporator
b. single effect evaporator
b. single-effect evaporator
In evaporation operation, the valuable product is called
a. thick liquor
b. vapor
c. water
d. residue
a. thick liquor
For the same duty and heat transfer area, the feedforward flow evaporator is __________ compared to the backward flow evaporator in terms of heat transfer.
a. more efficient
b. less efficient
c. just the same
d. none of these
b. less effcient
For the same duty and heat transfer area, the feedforward flow evaporator is __________ compared to the backward flow evaporator in terms of heat transfer.
a. more efficient
b. less efficient
c. just the same
d. none of these
b. less efficient
For the same duty and heat transfer area, the feedforward flow evaporator is __________ compared to the backward flow evaporator in terms of heat transfer.
a. more efficient
b. less efficient
c. just the same
d. none of these
b. less efficient
For the same duty and heat transfer area, the feedforward flow evaporator is __________ compared to the backward flow evaporator in terms of heat transfer.
a. more efficient
b. less efficient
c. just the same
d. none of these
b. less efficient
For the same duty and heat transfer area, the feedforward flow evaporator is __________ compared to the backward flow evaporator in terms of heat transfer.
a. more efficient
b. less efficient
c. just the same
d. none of these
b. less efficient
The temperature driving force in an evaporator is determined as the difference between the condensing steam temperature and
a. condenser temperature
b. boiling point of the solvent
c. boiling point of the solution
d. BPR of the solution
c. boiling point of the solution
If the solution to be evaporated tends to strongly scale or form salt, the type of evaporator to be recommended is
a. long tube vertical
b. horizontal tube
c. forced circulation
d. natural circulation
c. forced circulation
