MCQs of Heat Exchangers (Heat Transfer - 3151909)

Heat Transfer (3151909) MCQs

MCQs of Heat Exchangers

Showing 11 to 20 out of 32 Questions

11.

A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities $C_{m a x}$ and $C_{m i n}$ . The parameter NTU (number of transfer units ) used in the analysis of the heat exchanger is specified as

(a)	$\frac{A U}{C_{m i n}}$
(b)	$A U C_{m i n}$
(c)	$\frac{U}{A C_{m i n}}$
(d)	$\frac{A C_{m i n}}{U}$

12.

During the process of boiling and condensation, only a phase change takes place and one fluid remains at a constant temperature throughout the heat exchanger. In terms of the number of transfer units (NTU), the effectiveness of such an exchanger would be

(a)	$\frac{N T U}{1 + N T U}$
(b)	$1 - e x p (- N T U)$
(c)	$\frac{1 - e x p (- 2 N T U)}{2}$
(d)	cannot be worked out as the heat capacities are not known

13.

The equation of effectiveness $\in = 1 - e^{- N T U}$ for a heat exchanger is valid in case of

(a)	boiler and condenser for parallel flow
(b)	boiler and condenser for counterflow
(c)	boiler and condenser for both parallel and counter flow
(d)	gas turbine for both parallel and counter flow

14.

$\in - N T U$ method is particularly useful in the thermal design of heat exchanger when

(a)	the outlet temperatures of the fluid streams are not known as a priori
(b)	the outlet temperatures of the fluid streams are known as a priori
(c)	the outlet temperatures of the hot fluid stream are known but that cold fluid stream is not known as a priori
(d)	the inlet temperatures of the fluid streams are not known as a priori

15.

Which of the following terms is not associated with heat exchangers?

(a)	fouling
(b)	Mc Adam $'$ s correction factor
(c)	NTU
(d)	capacity ratio

16.

The overall heat transfer coefficient for a shell and tube heat exchanger for clean surfaces is $u_{0} = 400 W / m^{2} K$ . The fouling after one year of operation is found to be $h_{0} = 2000 W / m^{2} K$ . The overall heat transfer coefficient at this time is

(a)	$1200 W / m^{2} K$
(b)	$894 W / m^{2} K$
(c)	$333 W / m^{2} K$
(d)	$287 W / m^{2} K$

17.

A correction of LMTD is necessary in case of ................ heat exchanger

(a)	crossflow
(b)	parallel flow
(c)	counter current
(d)	All of these

18.

In a certain heat exchanger, both the fluid have identical mass flow rate specific heat product. The hot fluid enters at $76 ° C$ and leaves at $47 ° C$ and the cold fluid enters at $26 ° C$ and leaves at $55 ° C$ . The effectiveness of the heat exchanger is

(a)	0.58
(b)	0.68
(c)	1.5
(d)	2.58

19.

Consider the following is not an advantage of recuperator type heat exchanger?

more economical
more suitable for stationary plants
high heat transfer coefficient
less maintenance

Select the correct answer code:

(a)	1 and 3
(b)	1 and 2
(c)	2 and 4
(d)	3 and 4

20.

Air heaters are an example of

(a)	regenerator type heat exchangers
(b)	recuperative type heat exchangers
(c)	open type heat exchangers
(d)	combination of regenerator and recuperative type heat exchangers

Showing 11 to 20 out of 32 Questions