Water enters a tank from two pipes, one with a flow rate of 0.3 kg/s and the other with a flow rate of 0.1 kg / s. The tank has
1 answer:
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Answer:
a)75.8%
b)2.517KW/K
Explanation:
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To solve this problem follow the steps below
Through laboratory tests, thermodynamic tables were developed, these allow to know all the thermodynamic properties of a substance (entropy, enthalpy, pressure, specific volume, internal energy etc ..)
through prior knowledge of two other properties such as pressure and temperature.
1. use thermodynamic tables to find the following variables.
a.enthalpy and entropy at the turbine entrance
h1=Enthalpy(Water;T=500;P=6000)
=3422KJ/kg
s1=Entropy(Water;T=500;P=6000)
=6.881KJ/kgK
b. enthalpy and ideal entropy at the turbine outlet
h2i=Enthalpy(Water;s=6.881;P=20)
=2267KJ/kg
s2i=s1=6.881KJ/kgK
2. uses the output power and the first law of thermodynamics to find the real enthalpy at the turbine's output
W=m(h1-h2)
h2=h1-W/m
h2r=3422-2626/3=2546.6KJ/kg
3.
find efficiency with the following equation
4.
find the real entropy at the turbine exit
s2=Entropy(Water;h=2546,6;P=20)=7.72KJ/kgK
5.Finally find the entropy generated, using the following equation
ΔS=m(s2-s1)=(3kg/s)(7.72 KJ/kgK-6.881 KJ/kgK)=2.517KW/K
Answer:
a) The minimum acceptable value is 387.5 HV using Vickers hardness test.
b) The minimum acceptable value is 39.4 HRC using Rockwell C hardness test.
Explanation:
To get the tensile strength of a material from its hardness, we multiply it by an empirical constant that depends on things like yield strength, work-hardening, Poisson's ratio and geometrical factors. The incidence of cold-work varies this relationship.
According to DIN 50150 (a conversion table for hardness), the constant for Vickers hardness is ≈ 3.2 (an empirical approximate):
According to DIN 50150, the constant for Rockwell C hardness test is ≈31.5 around this values of tensile strength: