Chapter 13 (HTRN) Flashcards
One of the reasons for insulating the pipes is
Heat loss from the surface is minimized
The rate of radiant energy, that is emitted by a surface at any temperature and in small wavelengths is found from the known rate of energy, that under the same conditions will be emitted from a black surface, by multiplying with the absorptivity. The above enunciation is called:
Kirchoff’s Law
Which of the following is generally used to measure the temperature inside the furnace?
Optical Pyrometer
All heat transfer processes:
involve temperature difference between the bodies
What is thermal diffusivity ?
a physical property of the material
Which of the following is a unit of thermal diffusivity?
m²/hr
Non isotropic conductivity is shown by which of the following?
wood
For glass wool thermal conductivity changes from sample to sample due changes in:
structure, density, composition (all of the above)
Which of the following is the SI unit of thermal conductivity?
W/ m°K
What is the value if the Prandt’l number for air?
0.7
According to Prevost Theory of heat exchange;
all bodies absolute zero emit radiation
Thermal conductivity of wood depends in which of the following?
moisture, temperature, density
A fur coat on an animal will help the animal to remain:
warm in winter
The nature of flow of a fluid inside s tube, whether it is turbulent or laminar, can be ascertained by:
Reynolds number
Which of the following modes of heat transfer is the Stefan-Boltzmann law applicable?
Radiation
At all wave lengths and temperatures the monochromatic emissivity of a white body is equal to:
zero
The radiation from flames is having:
all of the above
The statement that the emissivity and absorptivity of a surface is surrounded by its own temperature are the same for both monochromatic and total radiation is called:
Kirchoff’s Law
A reservoir that supplies energy in the form of heat is called:
source
In regenerator type heat exchanger, heat transfer occurs by:
flow of hot and cold fluids alternately over surface
Least value of Prandt’l number can be expected in case of:
liquid metals
“The boiling point of a solution is a linear function of water at the same pressure.” The above statement is called
Dubring’s Rule
Floating heads are provided in heat exchangers to
avoid deformation of tubes because of thermal expansion
What do you call the first page of crystal formation?
nucleation
In heat exchanger design, one transfer unit implies:
condition when the change in temperature of one steam is numerically equal to the average driving force
Dritus Boelter equation can be applied in case of fluids flowing in:
turbulent region
In sugar mills can just is evaporated in:
long vertical tube evaporators
A 1-3 heat exchanger refers to which of the following?
single pass on shell side and double pass on tube side
A correction of LMTD is essential in case of:
cross flow heat exchanger
Which of the following is used as entrainer in acetic acid water separation?
Butyl acetate
A type of radiation consisting of singly charged particles that generate to intermediate distances
Beta radiation
An electrically charged atom or radical which carries electricity through an electrolyte is called:
ion
The energy of a body that can be transmitted in the form if heat
thermal energy
In an isometric process, the heat transferred is equal to:
change in internal energy
A substance that is able to absorb liquids ir gases and is used for removing them from a given medium or region
Absorbent
Radiant heat transfer is described by
Kirchoff’s Law
A reservoir that absorbs energy in the form of heat is called
sink
When the entire heat exchanger is selected as control volume, heat becomes
zero
Heat is conducted in the direction of
decreasing temperature
The heat transfer term in the first law of thermodynamics may be due to any of the following except:
internal heat generation (e.g., chemical reaction)
All heat transfer processes require a medium of energy exchange except:
radiation
Thermal conduction is described by
Fourier’s Law
Convection is described by which if the following laws?
Newton’s Law
Radiation heat transfer is described by
Kirchoff’s Law
The equivalent of ratio of emissive power to absorptivity for bodies in thermal equilibrium is described by:
Kirchoff’s Law
The temperature potential between temperature at the two ends of a heat exchanger are given by
the logarithmic mean temperature difference
The function of a heat exchanger is to
transfer heat from one fluid to another
The function of a superheater is to
exhange heat ti increase energy to the flow
A theoretical body which when heated to incandescence would emit a continuous light gray spectrum
Black body
Which of the following is the reason for insulating the pipes?
Heat loss from the surface is minimized
Heat transfer due to density differential
Convection
The term “exposure” in radiological effects is used as a measure of a gamma ray or an x ray field in the surface of an exposed object. Since this radiation produces ionization of the sir surrounding the object, the exposure is obtained as
number of ions produced per mass of air x coulumbs per kg
The passing of heat energy from molecule to molecule through a substance
conduction
The radiant heat transfer depends on
heat rays
What kind of heat exchanger where water is heated to a point that dissolved gases are liberated?
Deaerator