Why do engineers play a variety of roles in the engineering process?

Air at 1 atm enters a thin-walled ( 5-mm diameter) long tube ( 2 m) at an inlet temperature of 100°C. A constant heat flux is ap

alexdok [17]

Answer:

heat rate = 7.38 W

Explanation:

Given Data:

Pressure = 1atm

diameter (D) = 5mm = 0.005m

length = 2

mass flow rate (m) = 140*10^-6 kg/s

Exit temperature = 160°C,

At 400K,

Dynamic viscosity (μ) = 22.87 *10^-6

Prandtl number (pr) = 0.688

Thermal conductivity (k) = 33.65 *10^-3 W/m-k

Specific heat (Cp) = 1.013kj/kg.K

Step 1: Calculating Reynolds number using the formula;

Re = 4m/πDμ

= (4*140*10^-6)/(π* 0.005*22.87 *10^-6)

= 5.6*10^-4/3.59*10^-7

= 1559.

Step 2: Calculating the thermal entry length using the formula

Le = 0.05*Re*Pr*D

Substituting, we have

Le = 0.05 * 1559 * 0.688 *0.005

Le = 0.268

Step 3: Calculate the heat transfer coefficient using the formula;

Nu = hD/k

h = Nu*k/D

Since Le is less than given length, Nusselt number (Nu) for fully developed flow and uniform surface heat flux is 4.36.

h = 4.36 * 33.65 *10^-3/0.005

h = 0.1467/0.005

h = 29.34 W/m²-k

Step 4: Calculating the surface area using the formula;

A = πDl

=π * 0.005 * 2

=0.0314 m²

Step 5: Calculating the temperature Tm

For energy balance,

Qc = Qh

Therefore,

H*A(Te-Tm) = MCp(Tm - Ti)

29.34* 0.0314(160-Tm) = 140 × 10-6* 1.013*10^3 (Tm-100)

0.921(160-Tm) = 0.14182(Tm-100)

147.36 -0.921Tm = 0.14182Tm - 14.182

1.06282Tm = 161.542

Tm = 161.542/1.06282

Tm = 151.99 K

Step 6: Calculate the rate of heat transferred using the formula

Q = H*A(Te-Tm)

= 29.34* 0.0314(160-151.99)

= 7.38 W

the Prandtl number using the formula

5 0

3 years ago

Which of the following statements about pitot-static systems is FALSE? a). A pitot probe measures the Total Pressure of the free

Pavlova-9 [17]

Answer:

C

Explanation:

Pitot tube:

Pitot tube is a device which is used to measure the velocity of flow by measuring pressure difference between the points.

As we know that stagnation pressure is the summation of dynamic and static pressure.

Stagnation pressure = Static pressure + Dynamic pressure

So

Dynamic pressure = Stagnation pressure - Static pressure

We know that dynamic pressure

$P_{dynamic}=\dfrac{\rho V^2}{2}$

On the other hand Pitot tube measure the dynamic pressure.

So option C is correct.

5 0

3 years ago

To convert a whole number to a fraction the number can be written over a denominator of

exis [7]

One

When you convert a whole number into a fraction, you put the whole number as the numerator and the denominator as 1.

Such as 12=12/1 or 5=5/1

7 0

3 years ago

The atmosphere is divided into different layers, each with a different function. The stratosphere contains the ozone (O3).

tangare [24]

Answer:

a) At about 15 to 35 km from the Earth

b) It helps to absorb most of the ultraviolet rays from the sun, that is otherwise too dangerous here on Earth.

c) The depletion of the ozone layer is due to free radical catalysts, like nitric oxide (NO), nitrous oxide (N2O), hydroxyl (OH), but majorly due to atomic chlorine (Cl), and atomic bromine (Br) finding their way up to the the ozone layer.

d) The refrigeration processes and the aerosol aligned industrial processes, are the major culprits.

Explanation:

a) The ozone layer is lies in the lower portion of the stratosphere, from an height of about 15 to 35 kilometers from the surface of the Earth.

b) The ozone layer contains a large portion of ozone, a molecule of oxygen containing three oxygen atom bonded together. This ozone is created at this level by the action of ultraviolet radiation on an ordinary oxygen molecule, splitting it into two oxygen atom. Each of this oxygen atom then proceed to combine with another ordinary oxygen molecule, to form an ozone molecule. The ozone at this layer absorbs a large portion of the ultraviolet radiation from the sun.

c) The depletion of the ozone layer is due to the presence of some radical, that are able to survive up to the level of the ozone layer. At this level, ultraviolet radiation causes these these radicals to dissociate to give free bromine and chlorine mostly. This chlorine and bromine molecules breaks down the ozone molecules.

d) The various industrial processes includes refrigeration, and the aerosol industries that majorly releases the chlorofluorocarbons (CFCs) and bromofluorocarbons, which are the main culprits of ozone depletion.

5 0

3 years ago

Consider the simplicity of these two DOE examples. Next, consider the assertion that DOE isn’t put into practice as often or dee

Bingel [31]

Answer:

Do Re Mi

Explanation:

I have no clue sorry

5 0

4 years ago