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Q1. A shell-and-tube heat exchanger is used for the heating of oil from 15°C to 34°C; the oil flow rate is 16.0 litre/s (Cpo = 2.2 kJ/kg.K, density 880kg/m³). The heat exchanger has one shell pass and two tube passes. Hot water (Cpw = 4.18 kJ/kg.K, density 985kg/m³) enters the shell at 96 °C and leaves the shell at 65°C. The convective coefficient on the outside surface of the tubes is 1800 W/m² K, and 550 W/m².K on the inside surface of the tubes. The thermal resistance of the tube wall can be ignored. Determine a. the required water volume flow rate and the corrected logarithmic-mean temperature difference b. what is the required surface area for clean tubes in the heat exchanger? c. The tube may become unclean after a period of time, the fouling resistance may be up to 0.00015 m².K/W. What is the required surface area for the heat exchanger? d. why is correction factor needed? What are normally the reasons for fouling? Equations and Figures required for correction factor, from Welty Chapter 22. The parameters in Figures 22.9 and 22.10 are evaluated as follows: $Y = \frac{T_{out} - T_{in}}{T_{s,in} - T_{in}}$ (22-12) $Z = \frac{(\dot{m}c_p)_{tube}}{ (\dot{m}c_p)_{shell}} = \frac{C_t}{C_s} = \frac{T_{s,in} - T_{s,out}}{T_{t,out} - T_{t,in}}$ (22-13)

          Q1.
A shell-and-tube heat exchanger is used for the heating of oil from 15°C to 34°C; the oil flow rate is
16.0 litre/s (Cpo = 2.2 kJ/kg.K, density 880kg/m³). The heat exchanger has one shell pass and two tube
passes. Hot water (Cpw = 4.18 kJ/kg.K, density 985kg/m³) enters the shell at 96 °C and leaves the shell
at 65°C. The convective coefficient on the outside surface of the tubes is 1800 W/m² K, and 550
W/m².K on the inside surface of the tubes. The thermal resistance of the tube wall can be ignored.
Determine
a. the required water volume flow rate and the corrected logarithmic-mean temperature
difference
b. what is the required surface area for clean tubes in the heat exchanger?
c. The tube may become unclean after a period of time, the fouling resistance may be up to
0.00015 m².K/W. What is the required surface area for the heat exchanger?
d. why is correction factor needed? What are normally the reasons for fouling?
Equations and Figures required for correction factor, from Welty Chapter 22.
The parameters in Figures 22.9 and 22.10 are evaluated as follows:
$Y = \frac{T_{out} - T_{in}}{T_{s,in} - T_{in}}$ (22-12)
$Z = \frac{(\dot{m}c_p)_{tube}}{ (\dot{m}c_p)_{shell}} = \frac{C_t}{C_s} = \frac{T_{s,in} - T_{s,out}}{T_{t,out} - T_{t,in}}$ (22-13)

Q1.
A shell-and-tube heat exchanger is used for the heating of oil from 15°C to 34°C; the oil flow rate is
16.0 litre/s (Cpo = 2.2 kJ/kg.K, density 880kg/m³). The heat exchanger has one shell pass and two tube
passes. Hot water (Cpw = 4.18 kJ/kg.K, density 985kg/m³) enters the shell at 96 °C and leaves the shell
at 65°C. The convective coefficient on the outside surface of the tubes is 1800 W/m² K, and 550
W/m².K on the inside surface of the tubes. The thermal resistance of the tube wall can be ignored.
Determine
a. the required water volume flow rate and the corrected logarithmic-mean temperature
difference
b. what is the required surface area for clean tubes in the heat exchanger?
c. The tube may become unclean after a period of time, the fouling resistance may be up to
0.00015 m².K/W. What is the required surface area for the heat exchanger?
d. why is correction factor needed? What are normally the reasons for fouling?
Equations and Figures required for correction factor, from Welty Chapter 22.
The parameters in Figures 22.9 and 22.10 are evaluated as follows:
Y = (Tout - Tin)/(Ts,in - Tin) (22-12)
Z = ((ṁcp)tube)/( (ṁcp)shell) = (Ct)/(Cs) = (Ts,in - Ts,out)/(Tt,out - Tt,in) (22-13)

Added by Diego F.

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