5. combustion gases enter a gas turbine at 627 c and 1.2 mpa at a rate of 2.5 kg/s and leave at 527 c and 500 kpa. it is estimated that heat is lost from the turbine at a rate of 20 kw. using air properties for the combustion gases and assuming the surroundings to be at 25 c and 100 kpa, determine

This Question is incomplete.The complete question is

Combustion gases enter a gas turbine at 627∘C and 1.2 MPa at a rate of 2.5 kg/s and leave at 527∘C and 500 kPa. It is estimated that heat is lost from the turbine at a rate of 20 kW. Using air properties for the combustion gases and assuming the surroundings to be at 25∘C and 100 kPa, determine (a) the actual and reversible power outputs of the turbine. (b) the exergy destroyed within the turbine, and (c) the second-law efficiency of the turbine.

(a) W=257.5kW      Wrev=367.3kW

(b) X=109.8kW

(c) n=0.7

Explanation:

For Part(a)

Actual power output is determined from the energy balance. The final and initial enthalpy are taken from A-17 for the given temperature

mh₁=W+Q+mh₂

W=m(h₁-h₂)-Q

W=2.5(939.93-821.95)-20

W=257.5kW

The reversible power output is determined from the rate of energy destruction

Wrev=W+X

Wrev=W+T₀(m(s₂-s₁-Rln(p₂/p₁)+Q/T₀)

Wrev=257.5+298( 2.5 (2.71787-2.84856-0.287*ln(500/1200)+20/298)

Wrev=367.3kW

For part(b)

X=Wrev-W

X=367.3-257.5

X=109.8kW

For part (c)

Second-law efficiency is determined from the ratio of the actual and reversible power output:

n=W/Wrev

n=257.5/367.3

n=0.7

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.

d eras and periods