Chemical Heat Transfer

A. Economy of a multiple effect evaporator is not influenced by the boiling point elevation
B. Two identical cubes of iron and copper will have the same heat content under the same
conditions of temperature
C. Double pipe heat exchangers are mostly used in the field of refrigeration
D. Finned tube heat exchangers are suitable for heating air by steam

A. Higher is the temperature of the radiating body, higher is the wavelength of radiation
B. Logarithmic mean area is used for calculating the heat flow rate through a thick walled
cylinder
C. The wavelength corresponding to maximum mono-chromatic emissive power increases with
rise in temperature
D. Solid angle subtended by the finite surface at the radiating element is called the angle of
incidence

A. ‘Solvates’ are chemical compounds formed by solute with their solvents. When water is the
solvent, then it is called a ‘hydrate’
B. In heat exchanger calculations (Δt) weighted is used in place of Δt, when it involves more
than one sequence of heating or cooling i.e., desuperheating & condensation or condensation
& sub-cooling
C. Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted
D. In case of short tube vertical evaporators, area of central downtake is about 50 to 100% of the
total tube cross-sectional area

A. Nu = (Re) (Pr) (Gz)
B. Nu = (Re) (Pr) (St)
C. Nu = (Re) (Pr)
D. Nu = (Pr) (St)

A. With change in temperature, the radiant energy emitted by a black body remains unchanged
B. Absorptivity of a body approaches unity in case of diffuse reflection
C. Absorptivity of a perfectly black body is unity
D. Value of Stefan-Boltzmann constant is 4.876 × 10-8 KCal/m2.hr.°K4

A. The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situation
B. Film co-efficient for vaporisation decreases as a result of vapor binding
C. In industrial practice, sub-cooling of condensate is required, when the condensate is a volatile
liquid and is to be transferred for storage
D. Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film coefficient,
which is higher

A. The controlling resistance in case of heating of air by condensing steam is in the air fil
B. The log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) passes through the heat exchanger at constant temperature
C. In case of a 1 – 2 shell and tube heat exchanger, the LMTD correction factor value increases
sharply, when a temperature cross occurs
D. Phase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature

A. Orifice baffles are never used in a shell and tube heat exchanger
B. Pressure drop on the shell side of a heat exchanger depends upon tube pitch also
C. In a horizontal tube evaporator, surface blanketing by air is avoided
D. Split ring type and pull through type floating heads are two commonly used floating heads is
heat exchangers

A. Reciprocal of the resistance to heat flow is called thermal conductance
B. Unit of thermal conductance is W/°K
C. Thermal conductance of a wall of thickness ‘L’, thermal conductivity ‘k’ and heat flow area ‘A’ is kL/A
D. None of these

A. Swenson-Walker crystalliser is a batch crystalliser
B. Super saturation of the solution is the driving potential for a crystal growth
C. The liquor left after the removal of crystals from a solution is called mother liquor
D. The first stage of crystal formation is called nucleation