21
Metals are good conductors of heat because
Answer: their atoms collide frequently
Questions
22
Total heat is the heat required to
Answer: convert water into steam and superheat it
24
The time constant of a thermocouple is
Answer: the time taken to attain 63.2% of the value of initial temperature difference
25
Heat flows from one body to other when they have
Answer: different temperatures
26
In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by
Answer: cm (thickness)
28
Which of the following is expected to have highest thermal conductivity
Answer: solid ice
29
Thermal conductivity of glass-wool varies from sample to sample because of variation in
Answer: all of the above.
30
Which of the following has maximum value of thermal conductivity
Answer: aluminium
31
Moisture would find its way into insulation by vapour pressure unless it is prevented by
Answer: a vapour seal
32
The ratio of heat flow Q1/Q2 from two walls of same thickness having their thermal conductivities as ATj - 2K2 will be
Answer: 2
35
Heat conducted througfi unit area and unit thick face per unit time when temperature difference between opposite faces is unity,is called
Answer: thermal conductivity
37
A non-dimensional number generally associated with natural convection heat transfer is
Answer: Grashoff number
38
In counter flow heat exchangers
Answer: both the fluids at inlet are in their hot¬test state
39
Fourier's law of heat conduction is valid for
Answer: one dimensional cases only
