Equivalent diameter for heat transfer calculation for a duct of square cross-section having each side as 'd' will be

For annular flow of a fluid, the ratio of the equivalent diameter for pressure drop calculation to the equivalent diameter for heat transfer calculation is

A

$$\frac{{{{\text{d}}_1}}}{{{{\text{d}}_1} + {{\text{d}}_2}}}$$

B

$$\frac{{{{\text{d}}_2}}}{{{{\text{d}}_1} + {{\text{d}}_2}}}$$

C

$$\frac{{{{\text{d}}_1} + {{\text{d}}_2}}}{{{{\text{d}}_1}}}$$

D

$$\frac{{{{\text{d}}_1} + {{\text{d}}_2}}}{{{{\text{d}}_2}}}$$

The length of each side of square A is increased by 100 percent to make square B. Again the length of each side of square B is increased by 50 percent to make square C. By what percent is the area of square C greater than the sum of the areas of square A and B?

A

75%

B

80%

C

85%

D

90%

In a shell and tube heat exchanger having square pitch, the shell side equivalent diameter is given by (where, P = pitch, d = outside diameter of the tube)

A

$$\frac{{4\left( {{{\text{p}}^2} - \pi {{\text{d}}^2}/4} \right)}}{{\pi {\text{d}}}}$$

B

$$\frac{{{{\text{p}}^2} - \pi {{\text{d}}^2}/4}}{{\pi {\text{d}}}}$$

C

$$\frac{{4{{\text{p}}^2}}}{{\pi {\text{d}}}}$$

D

$$\frac{{\pi {\text{d}}}}{{4{{\text{p}}^2}}}$$

The length of each of square A is increased by 100 percent to make square B.Again the length of the each side of square B is increased by 50 peacent to make square C.By of the area df square A and B?

A

75%

B

80%

C

85%

D

90%

The equivalent diameter for fluid flow through square cross section channel of side 'x', for pressure drop calculation purpose is given by

A

4x

B

2x

C

x

D

$$\sqrt {\text{x}} $$

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

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

In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones ; because the smaller diameter tubes

A

Are easier to clean

B

Are less prone to fouling

C

Can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less

D

None of these

The equivalent diameter for flow through a rectangular duct of width B and height H is

A

$$\frac{{{\text{HB}}}}{{2\left( {{\text{H}} + {\text{B}}} \right)}}$$

B

$$\frac{{{\text{HB}}}}{{{\text{H}} + {\text{B}}}}$$

C

$$\frac{{2{\text{HB}}}}{{{\text{H}} + {\text{B}}}}$$

D

$$\frac{{4{\text{HB}}}}{{{\text{H}} + {\text{B}}}}$$

Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is

A

Finned tube heat exchanger with air inside and steam outside

B

Finned tube heat exchanger with air outside and steam inside

C

Shell and tube heat exchanger with air inside tubes and steam on shell side

D

Shell and tube heat exchanger with air on shell side and steam inside tubes

Equivalent diameter for heat transfer calculation for a duct of square cross-section having each side as 'd' will be

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