A common process for increasing the moisture content of air is to bubble it through a column of water. The air bubbles are assum
ed to be spheres having an initial radius of 1.0 mm, and are in thermal equilibrium with the surrounding water. The saturation or equilibrium vapor pressure of water is temperature dependent, ranging from about 0.03 atm at 298 K to 1.0 atm at 373 K. The total pressure of the gas inside the air bubble is 1.0 atm, and will not change even as water evaporates into it. The bubbles initially contain some water vapor (along with the other components of air).
a. How will the final bubble radius vary i) with initial water vapor concentration in the bubble and ii) with bubble/water temperature?
b. Draw a picture of the physical system, and state at least five reasonable assumptions for the mass-transfer aspect of the water evaporation process. What coordinate system should be used?
c. What are the simplified differential forms of Fick's flux equation for water vapor (species A), the general differential equation for mass transfer in terms of concentration CA, and a resulting expression that combines the two (don't worry if it can't be too simplified).
d. Propose reasonable boundary and initial conditions
a. How will the final bubble radius vary i) with initial water vapor concentration in the bubble and ii) with bubble/water temperature?
b. Draw a picture of the physical system, and state at least five reasonable assumptions for the mass-transfer aspect of the water evaporation process. What coordinate system should be used?
c. What are the simplified differential forms of Fick's flux equation for water vapor (species A), the general differential equation for mass transfer in terms of concentration CA, and a resulting expression that combines the two (don't worry if it can't be too simplified).
d. Propose reasonable boundary and initial conditions
1 answer:
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Answer:
Minimum electrical power required = 3.784 Watts
Minimum battery size needed = 3.03 Amp-hr
Explanation:
Temperature of the beverages,
Outside temperature,
rate of insulation,
To get the minimum electrical power required, use the relation below:
V = 5 V
Power = IV
If the cooler is supposed to work for 4 hours, t = 4 hours
Minimum battery size needed = 3.03 Amp-hr
Answer:
stress_ac = 5.333 MPa
shear stress_c = 1.763 MPa
Explanation:
Given:
- The missing figure is in the attachment.
- The dimensions of member AC = ( 6 x 25 ) mm x 2
- The diameter of the pin d = 19 mm
- Load at point A is P = 2 kN
Find:
- Find the axial stress in AE and the shear stress in pin C.
Solution:
- The stress in member AE can be calculated using component of force P along the member AE as follows:
stress_ac = P*cos(Q) / A_ae
Where, Angle Q: A_E_B and A_ac: cross sectional area of member AE.
cos(Q) = 4 / 5 ..... From figure ( trigonometry )
A_ae = 0.006*0.025*2 = 3*10^-4 m^2
Hence,
stress_ae = 2*(4/5) / 3*10^-4
stress_ae = 5.333 MPa
- The force at pin C can be evaluated by taking moments about C equal zero:
(M)_c = P*6 - F_eb*3
0 = P*6 - F_eb*3
F_eb = 0.5*P
- Sum of horizontal forces for member AC is zero:
P - F_eb - F_c = 0
F_c = 0.5*P
- The shear stress of double shear bolt is given by an expression:
shear stress = shear force / 2*A_pin
Where, The area of the pin C is:
A_pin = pi*d^2 / 4
A_pin = pi*0.019^2 / 4 = 2.8353*10^-4 m^2
Hence,
shear stress = 0.5*P / 2*A_pin
shear stress = 0.5*2 / 2*2.8353*10^-4
shear stress = 1.763 MPa
