- A. 20°C
- B. 40°C
- C. 60°C
- D. 66.7°C
Heat and Mass Transfer
A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100°C and leaves at 60°C. A cold fluid enters the heat exchanger at 40°C. The mean temperature difference between the two fluids is_____.
In heat exchangers, degree of approach is defined as the difference between temperatures of_____.
- A. Cold water inlet and outlet
- B. Hot medium inlet and outlet
- C. Hot medium outlet and cold water inlet
- D. Hot medium outlet and cold water outlet
In regenerator type heat exchanger, heat transfer takes place by_____.
- A. Direct mixing of hot and cold fluids
- B. A complete separation between hot and cold fluids
- C. Flow of hot and cold fluids alternately over a surface
- D. Generation of heat again and again
In a shell and tube heat exchanger, baffles are provided on the shell side to_____.
- A. Improve heat transfer
- B. Provide support for tubes
- C. Prevent stagnation of shell side fluid
- D. All of these
Fouling factor is used_____.
- A. In heat exchanger design as a safety factor
- B. In case of Newtonian fluids
- C. When a liquid exchanges heat with a gas
- D. None of the above
Heat flows from one body to other when they have_____.
- A. Different heat contents
- B. Different specific heat
- C. Different atomic structure
- D. Different temperatures
Fourier’s law of heat conduction gives the heat flow for_____.
- A. Irregular surfaces
- B. Nonuniform temperature surfaces
- C. One dimensional cases only
- D. Two dimensional cases only
The natural convection air cooled condensers are used in_____.
- A. Domestic refrigerators
- B. Water coolers
- C. Room air conditioners
- D. All of these
The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to_____.
- A. -1/3
- B. -2/3
- C. 1
- D. -1
Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.
- A. Cold body to hot body
- B. Hot body to cold body
- C. Smaller body to larger body
- D. Larger body to smaller body