Question
Determine the average water exit velocity
Answer:
53.05 m/s
Explanation:
Given information
Volume flow rate, ![Q=16 m^{3}/min](https://tex.z-dn.net/?f=Q%3D16%20m%5E%7B3%7D%2Fmin)
Diameter d= 8cm= 0.08 m
Assumptions
- The flow is jet flow hence momentum-flux correction factor is unity
- Gravitational force is not considered
- The flow is steady, frictionless and incompressible
- Water is discharged to the atmosphere hence pressure is ignored
We know that Q=AV and making v the subject then
where V is the exit velocity and A is area
Area,
where d is the diameter
By substitution
![V=\frac {16\times 4}{\pi 0.08^{2}}=3183.098862 m/min](https://tex.z-dn.net/?f=V%3D%5Cfrac%20%7B16%5Ctimes%204%7D%7B%5Cpi%200.08%5E%7B2%7D%7D%3D3183.098862%20m%2Fmin)
To convert v to m/s from m/s, we simply divide it by 60 hence
![V=\frac {3183.098862 m/min}{60 s}=53.0516477 m/s\approx 53.05 m/s](https://tex.z-dn.net/?f=V%3D%5Cfrac%20%7B3183.098862%20%20m%2Fmin%7D%7B60%20s%7D%3D53.0516477%20m%2Fs%5Capprox%2053.05%20m%2Fs)
Answer:
if you're talking about the car b-post, the answer is "posts"
Explanation:
looked it up
Answer:
the overall heat transfer coefficient of this heat exchanger is 1855.8923 W/m²°C
Explanation:
Given:
d₁ = diameter of the tube = 1 cm = 0.01 m
d₂ = diameter of the shell = 2.5 cm = 0.025 m
Refrigerant-134a
20°C is the temperature of water
h₁ = convection heat transfer coefficient = 4100 W/m² K
Water flows at a rate of 0.3 kg/s
Question: Determine the overall heat transfer coefficient of this heat exchanger, Q = ?
First at all, you need to get the properties of water at 20°C in tables:
k = 0.598 W/m°C
v = 1.004x10⁻⁶m²/s
Pr = 7.01
ρ = 998 kg/m³
Now, you need to calculate the velocity of the water that flows through the shell:
![v_{w} =\frac{m}{\rho \pi (\frac{d_{2}^{2}-d_{1}^{2} }{4} )} =\frac{0.3}{998*\pi (\frac{0.025^{2}-0.01^{2} }{4}) } =0.729m/s](https://tex.z-dn.net/?f=v_%7Bw%7D%20%3D%5Cfrac%7Bm%7D%7B%5Crho%20%5Cpi%20%28%5Cfrac%7Bd_%7B2%7D%5E%7B2%7D-d_%7B1%7D%5E%7B2%7D%20%20%7D%7B4%7D%20%29%7D%20%3D%5Cfrac%7B0.3%7D%7B998%2A%5Cpi%20%28%5Cfrac%7B0.025%5E%7B2%7D-0.01%5E%7B2%7D%20%20%7D%7B4%7D%29%20%7D%20%3D0.729m%2Fs)
It is necessary to get the Reynold's number:
![Re=\frac{v_{w}(d_{2}-d_{1}) }{v} =\frac{0.729*(0.025-0.01)}{1.004x10^{-6} } =10891.4343](https://tex.z-dn.net/?f=Re%3D%5Cfrac%7Bv_%7Bw%7D%28d_%7B2%7D-d_%7B1%7D%29%20%7D%7Bv%7D%20%3D%5Cfrac%7B0.729%2A%280.025-0.01%29%7D%7B1.004x10%5E%7B-6%7D%20%7D%20%3D10891.4343)
Like the Reynold's number is greater than 10000, the regime is turbulent. Now, the Nusselt's number:
![Nu=0.023Re^{0.8} Pr^{0.4} =0.023*(10891.4343)^{0.8} *(7.01)^{0.4} =85.0517](https://tex.z-dn.net/?f=Nu%3D0.023Re%5E%7B0.8%7D%20Pr%5E%7B0.4%7D%20%3D0.023%2A%2810891.4343%29%5E%7B0.8%7D%20%2A%287.01%29%5E%7B0.4%7D%20%3D85.0517)
The overall heat transfer coefficient:
![Q=\frac{1}{\frac{1}{h_{1} }+\frac{1}{h_{2} } }](https://tex.z-dn.net/?f=Q%3D%5Cfrac%7B1%7D%7B%5Cfrac%7B1%7D%7Bh_%7B1%7D%20%7D%2B%5Cfrac%7B1%7D%7Bh_%7B2%7D%20%7D%20%20%7D)
Here
![h_{2} =\frac{kNu}{d_{2}-d_{1}} =\frac{0.598*85.0517}{0.025-0.01} =3390.7278W/m^{2}C](https://tex.z-dn.net/?f=h_%7B2%7D%20%3D%5Cfrac%7BkNu%7D%7Bd_%7B2%7D-d_%7B1%7D%7D%20%3D%5Cfrac%7B0.598%2A85.0517%7D%7B0.025-0.01%7D%20%3D3390.7278W%2Fm%5E%7B2%7DC)
Substituting values:
![Q=\frac{1}{\frac{1}{4100}+\frac{1}{3390.7278} } =1855.8923W/m^{2} C](https://tex.z-dn.net/?f=Q%3D%5Cfrac%7B1%7D%7B%5Cfrac%7B1%7D%7B4100%7D%2B%5Cfrac%7B1%7D%7B3390.7278%7D%20%20%7D%20%3D1855.8923W%2Fm%5E%7B2%7D%20C)