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insens350 [35]
3 years ago
13

For a steel alloy it has been determined that a carburizing heat treatment of 14 h duration at 809°C will raise the carbon conce

ntration to 0.54 wt% at a point 3.6 mm from the surface. Estimate the time necessary to achieve the same concentration at a 6.0 mm position for an identical steel and at a carburizing temperature of 1100°C. Assume that D0 is 2.5 × 10-5 m2/s and Qd is 120 kJ/mol.
Engineering
1 answer:
Yakvenalex [24]3 years ago
3 0

Answer:

t_2 = 27.7 hr

Explanation:

Given data:

carbon concentration  =  0.54%

from the relation given below calculate the time required to achieve concentration at 6.00 mm from surface

\frac{x^2}{Dt} = constant

D considered constant

\frac{x^2}{t} =  constant

here, x POSITION FROM SURFACE, t is time required to achieve concentration

\frac{x_1^2}{t_1} = \frac{x_2^2}{t_2}

\frac{3.6^2}{14} = \frac{6^2}{t_2}

t_2 = 27.7 hr

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Convection is a function of temperature to the fourth power. a)-True b)-False
strojnjashka [21]

Answer:

The given statement for temperature and convection is False.

Explanation:

Convection is not a function of temperature to the fourth power but it depends linearly on temperature. the below equation shows the linear relation of heat transfer due to convection and temperature:

Q = H_{c}A(T_{hot} - T_{cold} )

Whereas, radiation is a function of temperature to the fourth power.

The Stefan-Boltzmann law gives the relationship between an object's temperature and the amount of radiation it emits. The law is given by:

Q=\sigma T^{4}

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3 years ago
A petrol engine produces 20 hp using 35 kW of heat transfer from burning fuel. What is its thermal efficiency, and how much powe
hoa [83]

Answer:

efficiency =42.62%

AMOUNT OF POWER REJECTED IS 20.080 kW

Explanation:

given data:

power 20 hp

heat energy = 35kW

power production = 20 hp = 20* 746 W = 14920 Watt   [1 hp =746 watt]

efficiency = \frac{power}{heat\ required}

efficiency = \frac{14920}{35*10^3}

                = 0.4262*10^100

                 =42.62%

b) heat\ rejected = heat\ required - amount\ of\ power\ generated

                           = 35*10^3 - 14920

                           = 20.080 kW

AMOUNT OF POWER REJECTED IS 20.080 kW

5 0
3 years ago
10. True or False: You should select your mechanic before you experience vehicle failure.
ra1l [238]

Answer:

True

Explanation:

Always see a professional if you have any issues that is not in your scope of practice

7 0
3 years ago
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Following lockout/tagout (LOTO) procedures is important but not required when working with dangerous
Stella [2.4K]

Answer:

False.

Explanation:

Employees working with dangerous machines and hazardous energy are required to know and follow LOTO procedures in order to ensure the safety of themselves and fellow employees. Employers are also required to train employees in LOTO procedures to ensure they know, understand, and are able to follow the applicable provisions of LOTO procedures.

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3 years ago
The mean of 10 numbers is 9, then the sum (total) of these numbers will be​
qwelly [4]

Answer:

90

Explanation:

mean is basically taking the sum of all numbers and then dividing the sum with the number of all given numbers..

here, the mean is 9, total numbers are 10.. so the sum will be 9 multiplied by 10, that is 90.

5 0
2 years ago
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