Answer:
Option 2, In seismic areas, the most crucial requirement for precast concrete is to tie elements together laterally
Explanation:
In seismic areas, the in-plane lateral forces are very larger and hence in order to restrict the lateral movement governed by the lateral force, lateral ties are essential .
Specific design detailing such as interior and perimeter ties in the floors causes diaphragm behavior and hence distribute the load evenly without any movement.
Hence, option 2 is correct
A fuel oil is burned with air in a furnace. The combustion produces 813 kW of thermal energy, of which 65% is transferred as heat to boiler tubes that pass through the furnace. The combustion products pass from the furnace to a stack at 6500C. Water enters the boiler tubes as a liquid at 200C and leaves the tubes as saturated steam at 20 bar absolute. Calculate the rate (kg/h) at which steam is produced.
The rate at which steam is produced is equal to 701 kg/hour.
What is a Boiler?A Boiler may be characterized as a type of device or instrument that significantly transforms water into steam. There are two types of boiler are found. They are water tube boilers and fire tube boilers.
According to the question,
The power generated by combustion, W = 813kW.
The efficiency of the boiler, η = 65% = 0.65.
Temperature, To = 650°C.
Water enters the boiler tubes as a liquid, T1 = 20°C.
Water leaves the tubes as saturated steam, P2 = 20 bar.
The enthalpy of water at 20°C, [tex]h_1[/tex] = 83.9kJ/kg.
The enthalpy of water at 20 bar pressure, [tex]h_2[/tex] = 2797.29kJ/kg.
Enthalpy change can be calculated by ΔH = [tex]h_2-h_1[/tex]
= 2797.29kJ/kg - 83.9kJ/kg = 2713.3 kJ/kg.
The total energy that can be developed can be calculated by the formula:
Q = W × η = 813 × 0.65 = 528.45 kW.The mass of the flow rate of the rate at which steam is produced is calculated by the following formula:
[tex]m^.[/tex] = Q/ΔH= 528.45 kW/2713.3 kJ/kg.
= [tex]\frac{528.45kW }{2713.3kJ/kg} *\frac{3600kJ/h}{1kW}[/tex] = 701 kg/hour.
Therefore, the rate at which steam is produced is equal to 701 kg/hour.
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A piece of corroded steel plate was found in a submerged ocean vessel. It was estimated that the original area of the plate was 5 in.2 and that approximately 2.3 kg had corroded away during the submersion. Assuming a corrosion penetration rate of 200 mpy for this alloy in seawater, estimate the time of submersion in years. The density of steel is 7.9 g/cm3.
Answer:
the estimated time of submersion is 17.7 years
Explanation:
Given the data in the question;
estimate the time of submersion in years.
we write down the relation between time of submersion and corrosion penetration as follows;
CPR(mpy) = K × W(mg) / [ A(in²) × p(g/cm³) × t(hr) ]
we solve for t
t = (K × W) / ( AP × CPR )
given that;
Area A = 5 in²
W = 2.3 kg = 2.3 × 10⁶ mg
density of steel p = 7.9 g/cm³
CPR = 200
we know that K is 534
so we substitute
t = (534 × 2.3 × 10⁶ mg) / ( 5 in² × 7.9 g/cm³ × 200 mpy )
t = 1,228,200,000 / 7900
t = 155468.3544 hr
t = 155468.3544 hr × ( 1 yrs / ( 365 × 24 hrs )
t = 17.7 years
Therefore, the estimated time of submersion is 17.7 years
The atomic weights of C and H are 12 and 1, respectively. The chemical formula of polyethylene is (C2H4)n. The number average mean molecular weight of polyethylene with a degree of polymerization of 12,000 is:_____.
a. 120,000.
b. 336,000.
c. 280,000.
d. 296,000.
Answer:
b. 336,000.
Explanation:
Step 1: Calculate the molecular weight of the monomer
Polyethilene is a polymer with the formula (C₂H₄)ₙ, where C₂H₄ is the monomer and n is the number of monomers in the polymer. We can calculate the molecular weight of the monomer by addition of the weights of the atoms that form it.
MC₂H₄ = 2 × MC + 4 × MH
MC₂H₄ = 2 × 12 + 4 × 1 = 28
Step 2: Calculate the average molecular weight of polyethylene
The average degree of polymerization (DP) of polyethylene is 12,000. We can calculate the average molecular weight of polyethylene using the following expression.
DP = M(C₂H₄)ₙ/MC₂H₄
M(C₂H₄)ₙ = DP × MC₂H₄
M(C₂H₄)ₙ = 12,000 × 28 = 336,000
A screw extruder is 50 mm in diameter, 1 m long, has a 50mm lead, a channel 5 mm deep and a flight 3 mm wide. The circular die through which the extruded material forms the shape of a rod is of diameter 4 centimeters and length 5 cms. The viscosity of the thermoplastic fiber suspension that goes through the die to form the rod is 100 Pa.s.
If you want to manufacture 3600 solid rods of diameter 4 centimeters and length 25 cms each day in a shift of 10 hours what should be the RPM of the screw? Also find the power requirements for this extruder. What will be the pressure build up within the extruder?
Answer:
A) 105.7 rpm
B) 11.32 kw
C) 20.85 NPa
Explanation:
Number of solid rods to be manufactured = 3600
a) Determine the RPM of the screw
we will apply the relation below
discharge rate ( Qd ) = 0.5 π^2 * D^2 * N di * sinA * cos A ------- ( 1 )
where : D = 50 mm , di = 5 mm , N = ?
Tan A = p / πD = 50 / π*50 ∴ A = 17.65°
Insert values into equation ( 1 )
Qd = 17.83 * 10^-6 * N
required discharge rate ( Q ) = [tex]\frac{\frac{\pi D^2}{4}*L*N }{Time}[/tex] ------ ( 2 )
where : D = 0.01 , L = 25 * 10^-2 , N = 3600 , time = 10 * 3600
input value into 2
Q = 31.415 * 10^-6 m^3/s
Hence the RPM of the screw ( N )
= Q / Qd = 31.415 * 10^-6 / 17.83 * 10^-6 = 1.76 rev/s = 105.7 rpm
b) Determine the power requirements of the extruder
max power requirement = Pm * A * πDN / 60
= ( 20.85 * π * ( 50 )^2 / 4 ) * π * 150 *1.76
max power requirement = 11.32 kw
c) What is the pressure buildup within the extruder
Pressure buildup within the extruder = ( 6π*D*N*L* η * cot A ) / di^2
= ( 6π * 0.05 * 1.76 * 1 * 100 * cot17.65 ) / ( 5 * 10^-3 )^2
therefore ; Pm = 20.85 NPa
The 150 mm thick wall of a gas fired furnace is constructed of fireclay brick (k=1.5 W/m.K) , tho=2600 kg/m3, and cp=1000 J/kg.K ) and is well insulated at its outer surface. The wall is at a uniform initial temperature of 20 degree C, when the burners are fired and inner surface is exposed to products of combustion for which T infinity=950 degree C and h=100 W/ m2.K.
(A) How long does it take for the outer surface of the wall to reach a temperature of 750 degree C?
(B) plot the temperature distribution in the wall at the foregoing time.
Answer:
I am thick but I dont know the anwser
The time that it will take for the outer surface of the wall to reach a temperature of 750 degree C will be 33800 seconds.
How to calculate the time?Using the approximation methods, Fo will be;
= In(0.215/1.262)/(1.4289)²
= 0.867
Then, the time taken will be:
= 0.867(0.15)²/(1.5/2600 × 1000)
= 33800 seconds.
In conclusion, the time taken is 33800 seconds.
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