Concept explainers
Shell-and-tube heat exchangers with hundred of tubes housed in a shell are commonly used in practice for heat transfer between two fluids. Such a heat exchanger used in au active solar liot-watet system transfers heat froiui a water-atnifreeze solution flowing through the shell and the solar collector to fresh water flowing through the tubes at an average temperature of 64ƯC al a ¡‘ale of I S L’s. The heat exchangei’ contains 80 biass tubes I ciii in immer diameter and 1.5 in in length. Disregaidiiig inkt. exit, and header losses. detennine tite pressure drop across a single itibe and the pmnping power required by the rube-side finid of the heat exchaiiger.
After operating a long time. I-tutu-thick scale builds up on the inner surfaces with an equivalent rougluiess of 0.4 mm.
For the saine pwnplng power input. detennine tIme percent reductiomi in the flow rate of water through the tubes.
The pressure drop across a single tube.
The plumbing power required by the tube side fluid of the heat exchanger.
The percent reduction in the flow rate of water through the tubes.
Answer to Problem 136P
The pressure drop across a single tube is
The plumbing power required by the tube side fluid of the heat exchanger is
The percent reduction in the flow rate of water through the tubes is
Explanation of Solution
Given information:
The average temperature of water flowing through the tubes is
Write the expression for the average velocity.
Here, volume flow rate of fluid is
Write the expression of total area of tubes.
Here, the number of tube is
Write the expression for the Reynolds number.
Here, the density of fluid is
Write the expression for the Colebrook equation.
Here, the friction factor is
Write the expression for the pressure drop.
Here, the friction factor is
Write the expression for the pumping power.
Here, volume flow rate of fluid is
Write the expression of percentage reduction in flow rate.
Here, the given flow rate is
Substitute
Substitute
Refer table 3E "Properties of water" to find the dynamic viscosity of water corresponding to
Substitute,
Refer Table 8-2 "Equivalence roughness values for new commercial pipes" to find the value of roughness is
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute,
Substitute
Substitute
Substitute
There are five Equations (VIII), (IX), (X), (XI) and (XII) with five unknowns
Use the trial and error method to find the values.
Assume
Substitute
Substitute
Substitute
Substitute
Substitute
By substituting
Now use
Substitute
Substitute
Substitute
Substitute
Substitute
Now, By substituting
The values of
The value of
The value of
The value of
And the value of
Substitute
Conclusion:
The pressure drop across a single tube is
The plumbing power required by the tube side fluid of the heat exchanger is
The percent reduction in the flow rate of water through the tubes is
Want to see more full solutions like this?
Chapter 8 Solutions
Fluid Mechanics: Fundamentals and Applications
- Water flowing in a long, aluminum lube is to be heated by air flowing perpendicular to the exterior of the tube. The ID of the tube is 1.85 cm, and its OD is 2.3 cm. The mass flow rate of the water through the tube is 0.65kg/s, and the temperature of the water in the lube averages 30C. The free-stream velocity and ambient temperature of the air are 10m/sand120C, respectively. Estimate the overall heat transfer coefficient for the heat exchanger using appropriate correlations from previous chapters. State all your assumptions.arrow_forward10.1 In a heat exchanger, as shown in the accompanying figure, air flows over brass tubes of 1.8-cm 1D and 2.1-cm OD containing steam. The convection heat transfer coefficients on the air and steam sides of the tubes are , respectively. Calculate the overall heal transfer coefficient for the heal exchanger (a) based on the inner tube area and (b) based on the outer tube area.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning