In the calculation of Heat Transfer Coefficient on the annulus side for heat transferred to the inner tube, which is the correct formula for equivalent diameter De?

Consider we have a Double Pipe Heat Exchanger, with the inner tube of Outer diameter 20mm (thickness 2mm) and outer tube of inner diameter 30mm. We have two fluids A & B, we desire to have their flow rates as 15 Kg/s and 21 Kg/s respectively. Calculate the convective heat transfer coefficient from tube to annulus side. (Given Nusselt number on tube side = 496 and K = 15W/mK)

A

2067 W/m2K

B

1653 W/m2K

C

1623 W/m2K

D

1673 W/m2K

A single pass shell and tube heat exchanger, consisting of a bundle of 100 tubes (inner diameter 25 mm and thickness 2 mm) is used for heating 28 kg/s of water from 25 degree Celsius to 75 degree Celsius with the help of a steam condensing at atmospheric pressure on the shell side with condensing heat transfer coefficient 5000 W/m2 degree. Make calculation for overall heat transfer coefficient based on the inner area. Take fouling factor on the water side to be 0.002 m2 degree/W per tube and neglect effect of fouling factor on the shell side and thermal resistance of the tube wall

A

647.46 W/m2 degree

B

747.46 W/m2 degree

C

847.46 W/m2 degree

D

947.46 W/m2 degree

Consider we have a Double Pipe Heat Exchanger, with the inner tube of Outer diameter 20mm (thickness 2mm) and outer tube of inner diameter 30mm. We have two fluids A & B, we desire to have their flow rates as 15Kg/s and 21Kg/s respectively. What is the value of Hydraulic diameter for the annulus tube?

A

20mm

B

15mm

C

25mm

D

10mm

In a counter flow heat exchanger, water flowing through a tube of 10 cm inner diameter is heated by steam condensing on the outside of the tube. The convective film coefficient on the water and steam side are estimated to be 12000 and 20000 k J/m2 hr degree. Neglecting tube thickness and its resistance to heat flow, workout the overall heat transfer coefficient for the heat exchanger

A

4500 k J/m2 hr degree

B

5500 k J/m2 hr degree

C

6500 k J/m2 hr degree

D

7500 k J/m2 hr degree

Consider we have a Double pipe Heat Exchanger, with inner tube of diameter 20mm (neglect thickness) and outer tube of diameter 30mm. We have two fluids A & B (KA = 15W/mK and KB = 20W/mK) we desire to have their flow rates as 15m3/s and 21m3/s respectively. If their Nusselt number after calculation is Nui = 429 and Nuo = 530. What is the overall heat transfer coefficient of the equipment is no fouling exists?

A

168.4 W/m2K

B

168.4×103 KW/m2K

C

188.4 W/m2K

D

168.4 KW/m2K

A heating unit is made in the form of a vertical tube of 50 mm outside diameter and 1.2 m height. The tube is fitted with 20 steel fins of rectangular section with height 40 mm and thickness 2.5 mm. The temperature at the base of fin is 75 degree Celsius, the surrounding air temperature is 20 degree Celsius and the heat transfer coefficient between the fin as well as the tube surface and the surrounding air is 9.5 W/m2 K. If thermal conductivity of the fin material is 55 W/m K, find the amount of heat transferred from the tube without fin

A

118.44 W

B

98.44 W

C

8.44 W

D

908.44 W

A heating unit is made in the form of a vertical tube of 50 mm outside diameter and 1.2 m height. The tube is fitted with 20 steel fins of rectangular section with height 40 mm and thickness 2.5 mm. The temperature at the base of fin is 75 degree Celsius, the surrounding air temperature is 20 degree Celsius and the heat transfer coefficient between the fin as well as the tube surface and the surrounding air is 9.5 W/m2 K. If thermal conductivity of the fin material is 55 W/m K, find the amount of heat transferred from the tube with fin

A

1234 .98 W

B

1004.84 W

C

6539.83 W

D

3829.46 W

In the calculation of Reynold’s Number for the Friction factor of the annulus tube, which is the correct formula for equivalent diameter De?

A

$\frac{4×(D_{oi}^2 – D_{io}^2)×\frac{π}{4}}{π(D_{io})}$

B

$\frac{4×(D_{io}^2 – D_{oi}^2)×\frac{π}{4}}{π(D_{io})}$

C

$\frac{4×(D_{oi}^2 – D_{io}^2)×\frac{π}{4}}{π(D_{io}+D_{oi})}$

D

$\frac{4×(D_{io}^2 – D_{oi}^2)×\frac{π}{4}}{π(D_{io}+D_{oi})}$

The lubricating oil for a large industrial gas turbine engine is cooled in a counter flow, concentric tube heat exchanger. The cooling water flows through the inner tube ( diameter = 25 mm) with inlet temperature 25 degree celsius and mass flow rate 0.2 kg/s. The oil flows through the annulus (diameter = 50 mm) with mass flow rate 0.125 kg/s and its temperature at entry and exit are 90 degree Celsius and 60 degree Celsius. Find outlet temperature of cooling water

A

14.58 degree celsius

B

24.58 degree celsius

C

34.58 degree celsius

D

44.58 degree celsius

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

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

In the calculation of Heat Transfer Coefficient on the annulus side for heat transferred to the inner tube, which is the correct formula for equivalent diameter De?

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