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scZoUnD [109]
3 years ago
11

g Consider a thin opaque, horizontal plate with an electrical heater on its backside. The front end is exposed to ambient air th

at is 200C and provides a convection heat transfer coefficient of 10 W/m2K, solar irradiation of 600 W/m2, and an effective sky temperature of -400C. Calculate the electrical power (W/m2) required to maintain the plate surface temperature at Ts
Engineering
1 answer:
xxTIMURxx [149]3 years ago
3 0

Answer:

The electrical power is 96.5 W/m^2

Explanation:

The energy balance is:

Ein-Eout=0

qe+\alpha sGs+\alpha skyGsky-EEb(Ts)-qc=0

if:

Gsky=oTsky^4

Eb=oTs^4

qc=h(Ts-Tα)

\alpha s=\frac{\int\limits^\alpha _0 {\alpha l Gl} \, dl }{\int\limits^\alpha _0 {Gl} \, dl }

\alpha s=\frac{\int\limits^\alpha _0 {\alpha lEl(l,5800 } \, dl }{\int\limits^\alpha _0 {El(l,5800)} \, dl }

if Gl≈El(l,5800)

\alpha s=(1-0.2)F(0-2)+(1-0.7)(1-F(0-2))

lt= 2*5800=11600 um-K, at this value, F=0.941

\alpha s=(0.8*0.941)+0.3(1-0.941)=0.77

The hemispherical emissivity is equal to:

E=(1-0.2)F(0-2)+(1-0.7)(1-F(0-2))

lt=2*333=666 K, at this value, F=0

E=0+(1-0.7)(1)=0.3

The hemispherical absorptivity is equal to:

qe=EoTs^{4}+h(Ts-T\alpha  )-\alpha sGs-\alpha oTsky^{4}=(0.3*5.67x10^{-8}*333^{4})+10(60-20)-(0.77-600)-(0.3*5.67x10^{-8}*233^{4})=96.5 W/m^{2}

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Yield and tensile strengths and modulus of elasticity . with increasing temperature. (increase/decrease/independent)
meriva

Answer:

Yield strength, tensile strength decreases with increasing temperature and modulus of elasticity decreases with increasing in temperature.

Explanation:

The modulus of elasticity of a material is theoretically a function of the shape of curve plotted between the potential energy stored in the material as it is loaded versus the inter atomic distance in the material. The temperature distrots the molecular structure of the metal and hence it has an effect on the modulus of elasticity of a material.

Mathematically we can write,

E(t)=E_o[1-a\frac{T}{T_m}]

where,

E(t) is the modulus of elasticity at any temperature 'T'

E_o is the modulus of elasticity at absolute zero.

T_{m} is the mean melting point of the material

Hence we can see that with increasing temperature modulus of elasticity decreases.

In the case of yield strength and the tensile strength as we know that heating causes softening of a material thus we can physically conclude that in general the strength of the material decreases at elevated temperatures.

6 0
3 years ago
The type of current that flows from the electrode across the arc to the work is called what?
Scrat [10]

Answer:

Direct current.

Explanation:

5 0
3 years ago
Find the thickness of the material that will allow heat transfer of 6706.8 *10^6 kcal during the 5 months through the rectangle
Vinvika [58]

Answer:

The thickness of the material is 6.23 cm

Explanation:

Given;

quantity of heat, Q = 6706.8 *10⁶ kcal  

duration of the heat transfer, t = 5 months

thermal conductivity of copper, k = 385 W/mk

outside temperature of the heater, T₁ = 30° C

inside  temperature of the heater, T₂ = 50° C

dimension of the rectangular heater = 450 cm by 384 cm

1 kcal = 1.163000 Watt-hour

6706.8 *10⁶ kcal  = 7800008400 watt-hour

I month = 730 hours

5 months = 3650 hours

Rate of heat transfer, P = \frac{7800008400 \ Watt-Hour}{3650 \ Hours}  = 2136988.6 \ W

Rate of heat transfer, P = \frac{K*A *\delta T}{L}

where;

P is the rate of heat transfer (W)

k si the thermal conductivity (W/mk)

ΔT is change in temperature (K)

A is area of the heater (m²)

L is thickness of the heater (m)

P = \frac{KA(T_2-T_1)}{L} \\\\L =  \frac{KA(T_2-T_1)}{P}\\\\L =  \frac{385(4.5*3.84)(50-30)}{2136988.6}\\\\L = 0.0623 \ m

L = 6.23 cm

Therefore, the thickness of the material is 6.23 cm

8 0
3 years ago
Flip-flops are normally used for all of the following applications, except ________. logic gates data storage frequency division
SpyIntel [72]

Flip-flops are normally used for all of the following applications, except  logic gates.

<h3>What are Flip flops?</h3>

Flip flops are known to be tools that are used for counting. They come in different ranges.

Note that Flip flops are one that can be seen on counters, storage registers, and others and as such, Flip-flops are normally used for all of the following applications, except  logic gates.

Learn more about  Flip flops from

brainly.com/question/4237777

#SPJ1

6 0
1 year ago
Select three types of lines that engineers use to help represent the shape of a design in a sketch.
Vikki [24]

Hidden lines

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Extension lines:-

  • Used to explain the expansion of structures like building

Object lines

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