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Pachacha [2.7K]
3 years ago
15

A circular ceramic plate that can be modeled as a blackbody is being heated by an electrical heater. The plate is 30 cm in diame

ter and is situated in a surrounding ambient temperature of 15°C where the natural convection heat transfer coefficient is 12 W/m2·K. If the efficiency of the electrical heater to transfer heat to the plate is 80%, determine the electric power that the heater needs to keep the surface temperature of the plate at 220°C.
Engineering
1 answer:
denis23 [38]3 years ago
5 0

Answer:

Q = 125.538 W

Explanation:

Given data:

D = 30 cm

Temperature T_\infity = 15 degree celcius

T_S =  220 + 273 = 473 K

Heat coefficient = 12 W/m^2 K

Efficiency 80% = 0.8

Q = hA(T_S - T_{\infty}) \eta

= 12(\frac{\pi}{4} 0.3^2) (473 - 288) 0.8

Q = 125.538 W

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A large spherical tank contains gas at a pressure of 400 psi. The tank is constructed of high-strength steel having a yield stre
jok3333 [9.3K]

Answer:

t=2.025 inches

Explanation:

Given that

P = 400 Psi

Yield stress ,σ = 80 ksi

Diameter ,d= 45 ft

We know that

1 ft = 12 inches

d= 540 inches

Factor of safety ,K= 3

The required thickness given as

\dfrac {Pd}{4t}=\dfrac{\sigma}{K}

t=thickness

\dfrac {PdK}{4\sigma}=t

\dfrac {400\times 540\times 3}{4\times 80\times 1000}=t

t=2.025 inches

Therefore thickness will be 2.025 inches.

5 0
3 years ago
A sample of soil has a volume of 0.45 ft^3 and a weight of 53.3 lb. After being dried inan oven, it has a weight of 45.1 lb. It
topjm [15]

Answer:

a) the moisture content before it was placed in the oven is 18.18%

b) degree of saturation for soil is 72.19%

Explanation:

Given the data in the question;

Moisture Content = [(Weight of soil before dry - dry weight) / dry weight] × 100

so we substitute

Moisture content = [(53.3 - 45.1) / 45.1 ] × 100

= (8.2/45.1) × 100

= 18.18%

Therefore the moisture content before it was placed in the oven is 18.18%

Dry Unit Weight = dry weight / volume

Dry Unit Weight = 45.1 lb / 0.45 ft³

Dry Unit Weight = 100.22 lb/ft³

we know that;

dry unit weight = (Specific gravity × unit weight of water) / (1 + e)

we also know that; unit weight of water is 62.43 lbf/ft³

so we substitute

e = (2.70×62.43 / 100.22) - 1

e = 1.68 - 1

e = 0.68

so void ratio e = 0.68

Now we determine the degree of saturation using the equation;

degree of saturation = (Moisture content × specific gravity) / void ratio

we substitute

degree of saturation = ( 18.18% × 2.7) / 0.68

= 0.49086 / 0.68

= 0.7219 ≈ 72.19%

Therefore degree of saturation for soil is 72.19%

7 0
3 years ago
Which one of the following is a list of devices from least efficient to most efficient
Sergeu [11.5K]

Answer:

(A)-Light-Bulb, Automobile Engine, Power Plant, Electric Motor

Explanation:

To get the least efficient to the most efficient the chart below explains how to the get it

Incandescent light bulb-5%

Florescent light bulb-20%

Electric motor-90%

Power plant-35%

Automobile engine-25%

Home oil furnace-80%

4 0
3 years ago
If the specific surface energy for aluminum oxide is 0.90 J/m2 and its modulus of elasticity is (393 GPa), compute the critical
vampirchik [111]

Answer:

critical stress required for the propagation is 27.396615 ×10^{6} N/m²

Explanation:

given data

specific surface energy = 0.90 J/m²

modulus of elasticity E = 393 GPa = 393 ×10^{9} N/m²

internal crack length = 0.6 mm

to find out

critical stress required for the propagation

solution

we will apply here critical stress formula for propagation of internal crack

( σc ) = \sqrt{\frac{2E\gamma s}{\pi a}}    .....................1

here E is modulus of elasticity and γs is specific surface energy and a is half length of crack i.e 0.3 mm  = 0.3 ×10^{-3} m

so now put value in equation 1 we get

( σc ) = \sqrt{\frac{2E\gamma s}{\pi a}}

( σc ) = \sqrt{\frac{2*393*10^9*0.90}{\pi 0.3*10^{-3}}}

( σc ) = 27.396615 ×10^{6} N/m²

so critical stress required for the propagation is 27.396615 ×10^{6} N/m²

6 0
3 years ago
Write a program that removes all spaces from the given input. You may assume that the input string will not exceed 50 characters
GrogVix [38]

Answer:

Program that removes all spaces from the given input

Explanation:

// An efficient Java program to remove all spaces  

// from a string  

class GFG  

{  

 

// Function to remove all spaces  

// from a given string  

static int removeSpaces(char []str)  

{  

   // To keep track of non-space character count  

   int count = 0;  

 

   // Traverse the given string.  

   // If current character  

   // is not space, then place  

   // it at index 'count++'  

   for (int i = 0; i<str.length; i++)  

       if (str[i] != ' ')  

           str[count++] = str[i]; // here count is  

                                   // incremented  

         

   return count;  

}  

 

// Driver code  

public static void main(String[] args)  

{  

   char str[] = "g eeks for ge eeks ".toCharArray();  

   int i = removeSpaces(str);  

   System.out.println(String.valueOf(str).subSequence(0, i));  

}  

}  

5 0
3 years ago
Read 2 more answers
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