Process Heat Transfer Mid - I, September - 2014

1.Heat transfer describes the exchange of thermal energy, between physical systems depending on the
  • temperature
  • pressure
  • dissipating heat
  • All of the above
Answer: D
2.Heat transfer changes the internal energy of both systems involved according to the
  • First Law of Thermodynamics
  • Second Law of Thermodynamics
  • Third Law of Thermodynamics
  • None of the above
Answer: A
3.The thermodynamic free energy is the amount of work that a thermodynamic system can perform. Enthalpy is a thermodynamic potential, designated by
  • the letter "H", that is the sum of the internal energy of the system
  • (U) plus the product of pressure (P) and volume(V)
  • Joule is a unit to quantify energy, work, or the amount of heat
  • All of the above
Answer: D
4.The transfer of energy between an object and its environment, due to fluid motion. The average emperature, is a reference for evaluating properties related to convective heat transfer is called
  • Advection
  • Conduction or diffusion
  • Convection
  • Radiation
Answer: C
5.The ……………….. of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid evaporates resulting in an abrupt change in vapor volume
  • boiling point
  • humidity
  • melting point
  • pressure
Answer: A
6.What is heat flux?
  • The rate of heat transfer per unit area
  • The rate of heat transfer per meter area
  • The rate of heat transfer per km2 area
  • None of the above
Answer: A
7.log mean temperature diference used for?
  • Used to determine the mass transfer
  • Used to determine the heat transfer
  • Used to determine the momentum transfer
  • Used to determine the density transfe
Answer: B
8.The ratio of the time to reach thermal equilibrium perpendicular to the flow direction to the residence time is called
  • Prandtl number
  • Reynolds number
  • Nusselt number
  • Graetz number
Answer: D
9.Turbulence in tubes is
  • 2100 < Re < 4000
  • 100 < Re < 400
  • 1500 < Re < 2000
  • 100 < Re < 1000
Answer: A
10.The laminar boundary layer limit consists of which parameters:
  • the Prandtl number function which is valid for all values of the Prandtl number
  • the body-gravity function which accounts for the buoyancy induced fluid flow over the entire surface of the body
  • both a & b
  • None of the above
Answer: C
11.The fundamental modes of heat transferare conduction or diffusion, convection and ……………………..
Answer: Radiation
12.Thermal equilibrium is reached when all involved bodies and the surroundings reach the same temperature. Thermal expansion is the tendency of matter to change in ……………. in response to a change in temperature
Answer: Volume
13.prandtl number NPr = ...........................................
Answer: CP /k
14.……………… is the transport mechanism of a fluid substance or conserved property from one location to another, depending on motion and momentum.
Answer: Advection
15.The unts of heat‐transfer coefficient are ………………………………….
Answer: w/m2k
16.The units of thermal conductivity are ………………………….
Answer: w/mk
17.The fourier’s law of heat conduction is ……………………………..
Answer:
18.A boundary layer developing within which the velocity ranges from  = 0 at the wall to  = 0 is called …………………………………
Answer: Hydrodynamic boundary layer
19.A hot vertical plate in contact with air is an example of ……………………
Answer: Natural convection
20.A simple general model is developed to predict natural convection heat transfer from isothermal horizontal and vertical cuboids of arbitrary shape for a wide range of Rayleigh and ……………… numbers.
Answer: Prandtl