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3 years ago

15

Consider a flat plate that is 25 mm long, 30 mm wide, and 1 mm thick and a 50 mm long cylinder with the same volume as the plate

. Compare the heat transfer of the plate in parallel air flow to the heat transfer of the cylinder in cross flow under the same conditions. Both the plate and cylinder have a surface temperature of 80°C. The air is at 25°C with a velocity of 3 m/s. Note: Use the Churchill and Bernstein correlation to determine the Nusselt number for the cylinder case.

1 answer:

Blizzard [7]3 years ago

4 0

Answer:

Average heat transfer =42.448w/m^2k

Nud = 13.45978

Explanation:

See attachment for step by step guide

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The _____ is a voice for small business.

Sliva [168]

Answer:

The <u>National Federation of Independent Business (NFIB) </u>is a voice for small business

Explanation:

The National Federation of Independent Business is a not for profit business association with goal of supporting and upholding small business owners right to carry out their privately owned business, protecting them from excessive government intrusions into their businesses.

The association have their headquarters in Tennessee with offices in Washington DC and the capitals of the 50 state capitals making NFIB the most far-reaching and largest association for small business in the U.S.

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3 years ago

Create an abstract class DiscountPolicy. It should have a single abstract method computeDiscount that will return the discount f

eimsori [14]

Answer:

Java Code was used to define classes in the abstract discount policy,The bulk discount, The buy items get one free and the combined discount

Explanation:

Solution

Code:

Main.java

public class Main {

public static void main(String[] args) {

BulkDiscount bd=new BulkDiscount(10,5);

BuyNItemsGetOneFree bnd=new BuyNItemsGetOneFree(5);

CombinedDiscount cd=new CombinedDiscount(bd,bnd);

System.out.println("Bulk Discount :"+bd.computeDiscount(20, 20));

System.out.println("Nth item discount :"+bnd.computeDiscount(20, 20));

System.out.println("Combined discount :"+cd.computeDiscount(20, 20));

}

}

discountPolicy.java

public abstract class DiscountPolicy

{

public abstract double computeDiscount(int count, double itemCost);

}

BulkDiscount.java

public class BulkDiscount extends DiscountPolicy

{

private double percent;

private double minimum;

public BulkDiscount(int minimum, double percent)

{

this.minimum = minimum;

this.percent = percent;

}

at Override

public double computeDiscount(int count, double itemCost)

{

if (count >= minimum)

{

return (percent/100)*(count*itemCost); //discount is total price * percentage discount

}

return 0;

}

}

BuyNItemsGetOneFree.java

public class BuyNItemsGetOneFree extends DiscountPolicy

{

private int itemNumberForFree;

public BuyNItemsGetOneFree(int n)

{

itemNumberForFree = n;

}

at Override

public double computeDiscount(int count, double itemCost)

{

if(count > itemNumberForFree)

return (count/itemNumberForFree)*itemCost;

else

return 0;

}

}

CombinedDiscount.java

public class CombinedDiscount extends DiscountPolicy

{

private DiscountPolicy first, second;

public CombinedDiscount(DiscountPolicy firstDiscount, DiscountPolicy secondDiscount)

{

first = firstDiscount;

second = secondDiscount;

}

at Override

public double computeDiscount(int count, double itemCost)

{

double firstDiscount=first.computeDiscount(count, itemCost);

double secondDiscount=second.computeDiscount(count, itemCost);

if(firstDiscount>secondDiscount){

return firstDiscount;

}else{

return secondDiscount;

}

}

}

6 0

4 years ago

A flywheel made of Grade 30 cast iron (UTS = 217 MPa, UCS = 763 MPa, E = 100 GPa, density = 7100 Kg/m, Poisson's ratio = 0.26) h

hram777 [196]

Answer:

N = 38546.82 rpm

Explanation:

$D_{1}$ = 150 mm

$A_{1}= \frac{\pi }{4}\times 150^{2}$

= 17671.45 $mm^{2}$

$D_{2}$ = 250 mm

$A_{2}= \frac{\pi }{4}\times 250^{2}$

= 49087.78 $mm^{2}$

The centrifugal force acting on the flywheel is fiven by

F = M ( $R_{2}$ - $R_{1}$ ) x $w^{2}$ ------------(1)

Here F = ( -UTS x $A_{1}$ + UCS x $A_{2}$ )

Since density, $\rho = \frac{M}{V}$

$\rho = \frac{M}{A\times t}$

$M = \rho \times A\times t$ $M = 7100 \times \frac{\pi }{4}\left ( D_{2}^{2}-D_{1}^{2} \right )\times t$

$M = 7100 \times \frac{\pi }{4}\left ( 250^{2}-150^{2} \right )\times 37$

$M = 8252963901$

∴ $R_{2}$ - $R_{1}$ = 50 mm

∴ F = $763\times \frac{\pi }{4}\times 250^{2}-217\times \frac{\pi }{4}\times 150^{2}$

F = 33618968.38 N --------(2)

Now comparing (1) and (2)

$33618968.38 = 8252963901\times 50\times \omega ^{2}$

∴ ω = 4036.61

We know

$\omega = \frac{2\pi N}{60}$

$4036.61 = \frac{2\pi N}{60}$

∴ N = 38546.82 rpm

7 0

3 years ago

A plate of an alloy steel has a plane-strain fracture toughness of 50 MPa√m. If it is known that the largest surface crack is 0.

Ivahew [28]

Answer:

option B is correct. Fracture will definitely not occur

Explanation:

The formula for fracture toughness is given by;

K_ic = σY√πa

Where,

σ is the applied stress

Y is the dimensionless parameter

a is the crack length.

Let's make σ the subject

So,

σ = [K_ic/Y√πa]

Plugging in the relevant values;

σ = [50/(1.1√π*(0.5 x 10^(-3))]

σ = 1147 MPa

Thus, the material can withstand a stress of 1147 MPa

So, if tensile stress of 1000 MPa is applied, fracture will not occur because the material can withstand a higher stress of 1147 MPa before it fractures. So option B is correct.

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BigorU [14]

Answer: preventive maintenance

Explanation:

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