![University of Khartoum
Faculty of Engineering
Department of Mechanical Engineering
Second Semester 2018/2019
Fourth Year Selected Courses
Heat Exchangers; Sizing and Ratings
Homework No. 1
Due date: Wednesday February 12th
, 2020
Q1
Velocity and temperature profiles for laminar flow in a tube of radius ro = 10 mm
have the form
𝑢(𝑟) = 0.1[1 − (
𝑟
𝑟𝑜
)
2
]
𝑇(𝑟) = 344.8 + 75.0 (
𝑟
𝑟𝑜
)
2
− 18.8 (
𝑟
𝑟𝑜
)
4
With units of m/s and K, respectively. Determine the corresponding value of the
mean (or bulk) temperature, Tm at this axial position.
Q2
Water flowing at 2 kg/s through a 40-mm-diameter tube is to be heated from 25 to
75 °C by maintaining the tube surface temperature at 100 °C. What is the required
tube length for these conditions?
Q3
Hot air at atmospheric pressure and 85 °C enters a 10-m-long uninsulated square
duct of cross section 0.15 m x 0.15 m that passes through a space in a house at a
rate of 0.10 m3
/s. The duct is observed to be nearly isothermal at 70 °C. Determine
the exit temperature of the air and the rate of heat loss from the duct to the air in
the space.](https://image.slidesharecdn.com/homework01-211016121556/85/Homework-01-1-320.jpg)
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Homework 01
- 1. University of Khartoum Faculty of Engineering Department of Mechanical Engineering Second Semester 2018/2019 Fourth Year Selected Courses Heat Exchangers; Sizing and Ratings Homework No. 1 Due date: Wednesday February 12th , 2020 Q1 Velocity and temperature profiles for laminar flow in a tube of radius ro = 10 mm have the form 𝑢(𝑟) = 0.1[1 − ( 𝑟 𝑟𝑜 ) 2 ] 𝑇(𝑟) = 344.8 + 75.0 ( 𝑟 𝑟𝑜 ) 2 − 18.8 ( 𝑟 𝑟𝑜 ) 4 With units of m/s and K, respectively. Determine the corresponding value of the mean (or bulk) temperature, Tm at this axial position. Q2 Water flowing at 2 kg/s through a 40-mm-diameter tube is to be heated from 25 to 75 °C by maintaining the tube surface temperature at 100 °C. What is the required tube length for these conditions? Q3 Hot air at atmospheric pressure and 85 °C enters a 10-m-long uninsulated square duct of cross section 0.15 m x 0.15 m that passes through a space in a house at a rate of 0.10 m3 /s. The duct is observed to be nearly isothermal at 70 °C. Determine the exit temperature of the air and the rate of heat loss from the duct to the air in the space.