All categories

4 years ago

Why does an object under forced convection reach a steady-state faster than an object subjected to free-convection?

Engineering

1 answer:

bonufazy [111]4 years ago

5 0

Answer:

Free convection:

When heat transfer occurs due to density difference between fluid then this type of heat transfer is know as free convection.The velocity of fluid is zero or we can say that fluid is not moving.

Force convection:

When heat transfer occurs due to some external force then this type of heat transfer is know as force convection.The velocity of fluid is not zero or we can say that fluid is moving in force convection.

Heat transfer coefficient of force convection is high as compare to the natural convection.That is why heat force convection reach a steady-state faster than an object subjected to free-convection.

We know that convective heat transfer given as

q = h A ΔT

h=Heat transfer coefficient

A= Surface area

ΔT = Temperature difference

You might be interested in

For a bolted assembly with eight bolts, the stiffness of each bolt is kb = 1.0 MN/mm and the stiffness of the members is km = 2.

rjkz [21]

Answer:

a) 0.978

b) 0.9191

c) 1.056

d) 0.849

Explanation:

Given data :

Stiffness of each bolt = 1.0 MN/mm

Stiffness of the members = 2.6 MN/mm per bolt

Bolts are preloaded to 75% of proof strength

The bolts are M6 × 1 class 5.8 with rolled threads

Pmax =60 kN, Pmin = 20kN

a) Determine the yielding factor of safety

$n_{p} = \frac{S_{p}A_{t} }{CP_{max}+ F_{i} }$ ------ ( 1 )

Sp = 380 MPa, At = 20.1 mm^2, C = 0.277, Pmax = 7500 N, Fi = 5728.5 N

Input the given values into the equation above

equation 1 becomes ( np ) = $\frac{380*20.1}{0.277*7500*5728.5}$ = 0.978

note : values above are derived values whose solution are not basically part of the required solution hence they are not included

b) Determine the overload factor of safety

$n_{L} = \frac{S_{p}A_{t}-F_{i} }{C(P_{max} )}$ ------- ( 2 )

Sp = 380 MPa, At = 20.1 mm^2, C = 0.277, Pmax = 7500 N, Fi = 5728.5 N

input values into equation 2 above

hence : $n_{L}$ = 0.9191 $n_{L} = 0.9191$

C) Determine the factor of safety based on joint separation

$n_{0} = \frac{F_{i} }{P_{max}(1 - C ) }$

Fi = 5728.5 N, Pmax = 7500 N, C = 0.277,

input values into equation above

Hence $n_{0}$ = 1.056

D) Determine the fatigue factor of safety using the Goodman criterion.

nf = 0.849

attached below is the detailed solution .

4 0

3 years ago

Waterjet cutting uses a _____. a) Very-small-diameter jet of water that exits the cutting nozzle at approximately the speed of s

Paul [167]

Answer:

Explanation:

Waterjet cutting uses a very-small-diameter jet of water that exits the cutting nozzle at approximately the speed of sound. A water jet cutter, is oftentimes simply called a water jet is an industrial tool, like its name suggests, with the capabilities of cutting a different types of materials. Like its name suggests again, it uses water, although an extremely high-pressure jet of water to do the cutting. Other times, it uses a mixture of water and an abrasive substance to facilitate the cutting.

7 0

3 years ago

. For each of the following situations, determine if the diode below is in foward or reversebias(a) (2 points) V1 = 0 V, V2= 2V(

Mazyrski [523]

Assuming V1 is the anode and v2 the cathode (Anode is P region and Cathode is N)

Answer:

a) Reverse bias

b) Forward bias

c) Forward bias

Explanation:

Forward bias: It happens whenever the N region of the diode is more positive than the P region. Hence, the depletion zone increase ceasing the current through the circuit -> V1 -V2 < 0

Reverse bias: It happens whenever the P region of the diode is more positive than the N region. In this case, the depletion zone begins to shrink, if enough voltage is applied current could go through the circuit -> V1 - V2 > 0

a) V = V1 - V2 = 0 - 2 = -2 -> -2 is smaller than zero therefore, we have reverse bias

b) V = V1 - V2 = 4.5 - 2.8 = 1.7 -> 1.7 is greater than zero therefore, we have forward bias

c9 V = V1 - V2 = -1 - -1.3 = 0.3 -> 0.3 is greater than zero therefore, we have forward bias

6 0

3 years ago

The 2-kg package leaves the conveyor belt at with a speed of vA = 1 m/s and slides down the smooth ramp. Determine the required

Kisachek [45]

Answer:

Incomplete question: Find the normal reaction the curved portion of the ramp exerts on the package at B if pB = 2 m, the height is 4 m

Answer: The required speed is 8.9107 m/s

The normal reaction is 99.0006 N

Explanation:

Given data:

m = 2 kg

vA = speed = 1 m/s

h = 4 m

g = gravity = 9.8 m/s²

Questions: Determine the required speed of the conveyor, vc = ?

Find the normal reaction, Nc = ?

The required speed applying the conservation of energy:

$\frac{1}{2} mv_{A}^{2} +mgh=\frac{1}{2} mv_{c} ^{2}$

Solving for vc:

$v_{c} =\sqrt{v_{A}^{2}+2gh } =\sqrt{1^{2}+(2*9.8*4) } =8.9107m/s$

The normal reaction applying the equilibrium of forces:

$N_{c} -mg=m(\frac{v_{c}^{2} }{p_{B} } )$

$N_{c} =2*(\frac{8.9107^{2} }{2} )+(2*9.8)=99.0006N$

3 0

3 years ago

Name two types of fabric testers and explain how they work.

Lilit [14]

Answer:

Merchandisers are the key persons in apparel business. They work as a bridge between buyer and seller. Merchandisers have to do various tasks from order execution to final dispatch. Developing Lab dip is one of the primary jobs for a merchandiser to start an order execution. They need to run for lab dip approval. Though this would be an easy task, sometimes big mistakes may occur. They have to do different fabric tests as buyer required. In this article I will briefly described different types of fabric test are completed by garment merchandisers.

It is necessary to validate the information that the mill or manufacturer gives you. This is normally done by having fabric tested by an accredited testing house (internationally recognized) either in the country of manufacturer or locally in your head office. Some companies have their own equipment and employ qualified fabric technicians to carry out the testing at their headquarters. When using an accredited testing house, it will not matter in which country the test is done, because the test has to be carried out to the agreed method, and no matter which country does the test, it will be done in exactly the same way. As the fabric construction is such an important part of the garment, when finalized, the fiber composition, weight, and yarn count should be added to your contract with the supplier.

The testing house will give you guidance on the result you should be achieving and the method that you should be using.

4 0

4 years ago