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A composite wall is to be used to insulate a freezer chamber at -350C. Two insulating materials are to be used with conductiviti

choli [55]

Answer:

thickness1=1.4m

thickness2=2.2m

convection coefficient=0.33W/m^2K

Explanation:

you must use this equation to calculate the thickness:

L=K(T2-T1)/Q

L=thickness

T=temperature

Q=heat

L1=0.04*(0--350)/10=1.4m

L2=0.1(220-0)/10=2.2m

Then use this equation to calculate the convective coefficient

H=Q/(T2-T1)

H=10/(250-220)=0.33W/m^2K

7 0

3 years ago

A hot brass plate is having its upper surface cooled by impinging jet of air at temperature of 15°C and convection heat transfer

gulaghasi [49]

Answer:

809.98°C

Explanation:

STEP ONE: The first step to take in order to solve this particular Question or problem is to find or determine the Biot value.

Biot value = (heat transfer coefficient × length) ÷ thermal conductivity.

Biot value = (220 × 0.1)÷ 110 = 0.2.

Biot value = 0.2.

STEP TWO: Determine the Fourier number. Since the Biot value is greater than 0.1. Tis can be done by making use of the formula below;

Fourier number = thermal diffusivity × time ÷ (length)^2.

Fourier number = (3 × 60 × 33.9 × 10^-6)/( 0.1)^2 = 0.6102.

STEP THREE: This is the last step for the question, here we will be calculating the temperature of the center plane of the brass plate after 3 minutes.

Thus, the temperature of the center plane of the brass plane after 3 minutes = (1.00705) (0.89199) (900- 15) + 15.

= > the temperature of the center plane of the brass plane after 3 minutes = 809.98°C.

5 0

3 years ago

The critical resolved shear stress for a metal is 39 MPa. Determine the maximum possible yield strength (in MPa) for a single cr

damaskus [11]

Answer:

78 MPa

Explanation:

Given that the critical resolved shear stress for a metal is 39 MPa, the maximum possible yield strength for a single crystal of this metal is twice the critical resolved shear stress for the metal. The maximum yield yield strength for a single crystal of this metal that is pulled in tension ( $\sigma_y$ ) is given as:

$\sigma_y=2*critical\ resolved\ shear\ stress(\tau_{css})\\\\\sigma_y=2*\tau_{css}\\\\\sigma_y=2*39\\\\\sigma_y=78\ MPa$

4 0

3 years ago

Assume that television broadcasts are nonrival and nonexcludable (some TV stations, such as those on cable TV, are excludable, b

ryzh [129]

Answer: Advertising acts in a method similar to a fee. People who watch TV broadcasts must watch ADs. TV stations turn this into money by selling airtime to advertisers.

Explanation:

A non-rival good is a good whose consumption by one person does not reduce the remaining quantity available. An example is a street light.

For non-excludable goods, it is impossible to prevent everyone from enjoying the benefits of the good. An example is a lighthouse. This is where the free rider problem comes in.

A free rider is someone enjoying the benefits of a good without paying for it. When a good is both non-rival and non-excludable, it is convenient for consumers to enjoy the benefit without paying for it.

If TV broadcasts are both non-rival and non-excludable, everybody can choose to become a free rider. Advertising can solve this problem by converting free riders to potential buyers of goods or services advertised during broadcasts. This way, stations can generate revenue by selling airtime.

3 0

3 years ago

Read 2 more answers

Why can't I fly. I dont know why?

algol13

In order to fly, you must have a device/mechanism that will release hot air, causing it to fly. A jet pack will do the job.

5 0

3 years ago

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