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slega [8]
2 years ago
8

Imagine an ideal (Carnot) refrigerator that keeps helium in its liquid state, at a temperature of about 4.00 KK . The refrigerat

or, with the helium container inside, is in a laboratory where the temperature is about 294 KK . Because of the imperfection of the insulation, 2.00 JJ of heat is absorbed by the refrigerator each hour. How much electrical energy EEE must be used by the refrigerator to maintain a temperature of 4.00 KK inside for one hour
Engineering
1 answer:
masha68 [24]2 years ago
8 0

Known :

Tc = 4 K

Th = 294 K

Qc = 2 J

Solution :

Using COP definition

COP = Tc / (Th - Tc)

COP = 4 / (294 - 4)

COP = 2 / 145

COP = Qc / W

2 / 145 = 2 / W

W = 145 J

Electrical energy used

E = W / t

E = 145 / 1

E = 145 J/h

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natulia [17]

Answer:

minimum electric power consumption of the fan motor is 0.1437 Btu/s

Explanation:

given data

area = 3 ft by 3 ft

air density = 0.075 lbm/ft³

to find out

minimum electric power consumption of the fan motor

solution

we know that energy balance equation that is express as

E in - E out  = \frac{dE \ system}{dt}    ......................1

and at steady state  \frac{dE \ system}{dt} = 0

so we can say from equation 1

E in = E out

so

minimum power required is

E in = W = m \frac{V^2}{2} = \rho A V \frac{V^2}{2}  

put here value

E in =  \rho A V \frac{V^2}{2}  

E in =  0.075 *3*3* 22 \frac{22^2}{2}  

E in = 0.1437 Btu/s

minimum electric power consumption of the fan motor is 0.1437 Btu/s

5 0
3 years ago
An experiment to determine the convection coefficient associated with airflow over the surface of a thick stainless steel castin
Maksim231197 [3]

Answer:

h = 375 KW/m^2K

Explanation:

Given:

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steel thermal conductivity k = 15 W / mK

Thermo-couple temperature measurements: T_1 = 50 C , T_2 = 40 C

Air Temp T_∞ = 100 C

Assuming there are no other energy sources, energy balance equation is:

                                               E_in = E_out

                                        q"_cond = q"_conv

Since, its a case 1-D steady state conduction, the total heat transfer rate can be found from Fourier's Law for surfaces 1 and 2

q"_cond = k * (T_1 - T_2) / (L_2 - L_1) = 15 * (50 - 40) / (0.02 - 0.01)

=15KW/m^2

Assuming SS is solid, temperature at the surface exposed to air will be 60 C since its gradient is linear in the case of conduction, and there are two temperatures given in the problem. Convection coefficient can be found from Newton's Law of cooling:

q"_conv = h * ( T_∞  - T_s ) ----> h = q"_conv / ( T_∞  - T_s )

                                                   h = 15000 W / (100 - 60 ) C = 375 KW/m^2K

4 0
3 years ago
A power plant operates on a regenerative vapor power cycle with one open feedwater heater. Steam enters the first turbine stage
faltersainse [42]

Answer:

a) 0.489

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See the attachment for calculations

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All of the dimensions on an aircraft drawing are_________<br> to the bottom of the drawing.
Jet001 [13]
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2 years ago
What is the best way to submit your assignments?
Mrac [35]
A. Email your teacher right away. It would be the safest option.
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