A hot plate with a temperature of 60 C, 50 triangular profile needle wings of length (54 mm), diameter 10 mm (k = 204W / mK) wil
l be added and cooled. Ambient temperature is 20 C and heat transfer coefficient is 20 Since it is W / m2K; a-) Wing efficiency, b-) Total heat transfer rate (W) from the wings, c-) Calculate the effectiveness of a wing.
1 answer:
Complete question is;
A hot plate with a temperature of 60 °C will be cooled by adding 50 triangular profile needle blades (k = 204 W/m.K) with a length of 54 mm and diameter 10 mm. According to the ambient temperature 20 °C and the heat transfer coefficient on the surface 20 W/m².K. Calculate,
a-) Wing efficiency
b-) Total heat transfer rate (W) from the wings,
c-) Calculate the effectiveness of a wing.
Answer:
A) Efficiency = 96.05 %
B) Total heat transfer rate = 166.68 W/m
C) Wing Effectiveness = 10.42
Explanation:
Please find attached explanation for all the answers given.
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The answer is 380.32×10^-6
Refer below for the explanation.
Explanation:
Refer to the picture for brief explanation.
Answer:
The mass flow rate of refrigerant is 0.352 kg/s
Explanation:
Considering the cycle of an ideal heat pump, provided in the attachment, we first find enthalpy at state B and D. For that purpose, we use property tables of refrigerant R134a:
<u>At State A</u>:
From table, we see the enthalpy and entropy value of saturated vapor at 0.2 MPa. Therefore:
ha = 244.5 KJ/kg
Sa = 0.93788 KJ/kg.k
<u>At State B</u>:
Since, the process from state A to B is isentropic. Therefore,
Sb = Sa = 0.93788 KJ/Kg
From table, we see the enthalpy value of super heated vapor at 1 MPa and Sb. Therefore:
hb = 256.85 KJ/kg (By interpolation)
<u>At State C</u>:
From table, we see the enthalpy and entropy value of saturated liquid at 1 MPa. Therefore:
hc = 107.34 KJ/kg
Now, from the diagram it is very clear that:
Heat Loss = m(hb = hc)
m = (Heat Loss)/(hb - hc)
where,
m = mass flow rate = ?
Heat Loss = (180,000 Btu/hr)(1.05506 KJ/1 Btu)(1 hr/3600 sec)
Heat Loss = 52.753 KW
Therefore,
m = (52.753 KJ/s)/(256.85 KJ/kg - 107.34 KJ/kg)
<u>m = 0.352 kg/s</u>
Answer: c) 450 kPa
Explanation:
Boyle's Law: This law states that pressure is inversely proportional to the volume of the gas at constant temperature and number of moles.
(At constant temperature and number of moles)
where,
= initial pressure of gas = 150 kPa
= final pressure of gas = ?
= initial volume of gas = v L
= final volume of gas =
Therefore, the new pressure of the gas will be 450 kPa.