A pipe of 10 cm inner diameter is used to send crude oil over distance of 400 meters. The entire pipe was laid horizontal. The v
iscosity of the oil is 10 cp. The density of oil is 800 kg/m3 . a. (20 pts) The desired volumetric flow rate is 0.1 m3 /min. What is the Reynolds number of this flow? Is the flow laminar or turbulent? What is the pressure difference needed to generate this flow rate? b. (15 pts) Three month later, the operator found that they had to triple the pressure difference to maintain the flow rate at 0.1 m3 /min. The operator thought that wax deposition from the oil had reduced the inner diameter of the tube. Based on this assumption, can you estimate the reduced inner diameter of the tube? What is the Reynolds number of the flow?
1 answer:
Answer:
See explaination
Explanation:
Looking at Reynolds number, we can go ahead and describe the Reynolds number as a dimensionless value that is used to determine whether the fluid is exhibiting laminar flow (R less than 2300) or turbulent flow (R greater than 4000). Laminar flow is when a fluid moves smoothly and is predictable.
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Answer:
a)
b) %
Explanation:
A) First, let's write the energy balance:
(The enthalpy of an ideal gas is just function of the temperature, not the pressure).
The Cp of air is: 1.004 And its specific R constant is 0.287
.
The only unknown from the energy balance is , so it is possible to calculate it. The power must be negative because the work is done by the fluid, so the energy is going out from it.
B) The isentropic efficiency (e) is defined as:
Where is the isentropic enthalpy at the exit of the turbine for the isentropic process. The only missing in the last equation is that variable, because
can be obtained from the energy balance
An entropy change for an ideal gas with constant Cp is given by:
You can review its deduction on van Wylen 6 Edition, section 8.10.
For the isentropic process the equation is:
Applying logarithm properties:
Then,
So, now it is possible to calculate :
Finally, the efficiency can be calculated:
%