With respect to the statement Q - W = DeltaH. which of the following is true? Th

Question

With respect to the statement Q - W = DeltaH. which of the following is true? This is the 1st law applied to an open system This is the 1st law applied to an closed system This is the 2nd law applied to an open system This is the 2nd law applied to an closed system This represents a combination of the 1st and 2nd laws applied to any system A saturated mixture of water at 125 kPa has a specific entropy of 2.5 kJ/kgK. What is its specific enthalpy? 445kJ/kg 871kJ/kg 965kJ/kg 1252kJ/kg 2693kJ/kg A real turbine in a Rankine cycle power plant has an isentropic efficiency that is less than 1. Which one of the following statements is true? h2,a = h1 h2,a > h1 h2,a = h2s h2,a > h2s h2,a = 0

Explanation / Answer

a) first law applied to an open system .
as open system have flow work which is included in h= Pv+ u p, pv is flow work .in case of closed systems pv= 0;
b) saturated mixture
looka t water saturation table .find out H corresponding to that pressure and entropy
at this pressure S watr = 1.3741 Sfg= 5.91
1.37+ x* 5.91 = 2.5
x= .19 05 quality of micture
enthaly at this condition = 444.36+x* 2240.6= 871.211kj/kg

isoentropic efficency
= h1- h2a/( h1- h2s)
h2a>h1
h1>h2a>h2s
so option. image is not clear

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