Related Questions

The scales form in heat exchanges after a period of operation and provide additional resistance to heat transfer with some heat transfer coefficient . The reciprocal of this scale heat transfer coefficient is called .
A scaling factor
B forming factor
C resisting factor
D fouling factor
In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by
A Convection
B Radiation
C Conduction
D Both convection and conduction
Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the
A Surrounding temperature
B Average temperature of the fin
C Temperature of the fin end
D Constant temperature equal to that of the base
A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will
A decrease
B increase
C remain same
D heater will burn out
If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will
A Increase by 1.8 times
B Decrease by 22
C Increase by 216
D Remain unchanged
If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is
A 1
B 2
C $$\frac{1}{2}$$
D 4
For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of
A 1
B 1.74
C 6.1
D 37
If a single tube pass heat exchanger is converted to two passes; for the same flow rate, the pressure drop per unit length in tube side will __________ times.
A Increase by 1.8
B Decrease by 22
C Increase by 21.6
D None of these
If heater S is used on the third day and different heaters are used on the first and fourth days, then which heater is used on the first day?
A P
B Q
C R
D S
When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will
A Decrease
B Increase
C Remain constant
D None of the above

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