Chapter8-Geothermal Energy

Example 8.5.1-pg 450

In [1]:
##Ex8.5.1.;calculate: steam flow rate,cooling water flow,plant efficiency,Heat rate

##Enthalpy at point 1 at (31 kg/cm^2)=669.6 kcal/kg
##H1=H2=H3,enthalpy remain constant during throttling
H1=669.7;##unit= kcal/kg
H2=669.7;##unit= kcal/kg
H3=669.7;##unit= kcal/kg
##At point 3,
P3=9.55;##unit= kg/cm^2
##specific volume
vs3=0.22;##unit=m^3/kg
##Entropy
S3=1.580
T3=190.;##unit=degree C,(degree of superheat=13 degree C)
##S4_s at 0.34 kg/cm^2=S3
##x4_s=0.838
##and H4_s=hs+xL
H4_s=72.+(0.838*556)
print'%s %.2f %s'%(" H4_s=",H4_s," kcal/kg")
##Isentropic turbine work=H3-H4_s
ITW=H3-H4_s;
print'%s %.2f %s'%("\n Isentropic turbine work=",ITW," kcal/kg");
##Actual turbine work
ATW=0.80*ITW;
print'%s %.2f %s'%("\n Actual turbine work=",ATW," kcal/kg");
H4=669.7-ATW;
print'%s %.2f %s'%("\n H4=",H4," kcal/kg")
h5_6=72;##unit= kcal/kg; (Ignoring pump work)
##sensible heat   h7=h5=25 kcal/kg
h5=25;##unit=kcal/kg
h7=25;##unit=kcal/kg
##Turbine steam flow
TSF=(250*0.860*10**6)/(ATW*0.9);
print'%s %.2f %s'%("\n Turbine steam flow=",TSF," kg/hr");
##let
m4=TSF;
##Turbine volume flow
TVF=(TSF/60)*vs3;
print'%s %.2f %s'%("\n Turbine volume flow=",TVF," m^3/min");
##cooling water flow m7:m7(h5_6-h7)=m4(H4-h5_6)
m7=((H4-h5_6)/(h5_6-h7))*m4;
print'%s %.2f %s'%("\n cooling water flow m7=",m7," kg/hr");
Heat_added=H1-h5_6;
print'%s %.2f %s'%("\n Heat_added=",Heat_added," kcal/kg");
##plant efficiency=(Actual Turbine work*nmg)/Heat added
##nmg=combined mechanical and electrical efficiency of turbine-generator
nmg=0.90;
Plant_efficiency=(ATW*nmg)/Heat_added;
plant_efficiency=Plant_efficiency*100.;
print'%s %.2f %s'%("\n Plant Efficiency nplant=",plant_efficiency," persent");
##Plant heat rate=(860*Heat_added)/net_work
##net_work=105.36*0.90
Plant_heat_rate=(860./Plant_efficiency);
print'%s %.2f %s'%("\n Plant heat rate=",Plant_heat_rate," kcal/kWH");


##The value of "turbine steam flow" is wrong due to calculating mistak in textbook,due to which the further value related with it is given wrong
##The values are corrected in this program

 H4_s= 537.93  kcal/kg

 Isentropic turbine work= 131.77  kcal/kg

 Actual turbine work= 105.42  kcal/kg

 H4= 564.28  kcal/kg

 Turbine steam flow= 2266119.59  kg/hr

 Turbine volume flow= 8309.11  m^3/min

 cooling water flow m7= 23735548.77  kg/hr

 Heat_added= 597.70  kcal/kg

 Plant Efficiency nplant= 15.87  persent

 Plant heat rate= 5417.84  kcal/kWH

Example 8.5.2-pg460

In [2]:
##Ex8.5.2.;calculate: hot water flow,condenser cooling water flow,cycle efficiency,plant heat rate.
import math
H1=669.6;##unit=kcal/kg
H2=669.6;##unit=kcal/kg
##pressure at point 2,is 10.5 kg/cm^2;thus,
T2=195.;##unit=degree celcius; (14 degree celcius of superheat)
s2=1.567;
vsup=0.27;
x3s=0.832;
H3s=535.;##unit=kcal/kg
##Isentropic turbine work
ITW=H2-H3s;
print'%s %.2f %s'%(" Isentropic turbine work=",ITW," kcal/kg");
##Actual turbine work
ATW=0.65*ITW;
print'%s %.2f %s'%("\n Actual turbine work=",ATW," kcal/kg");
H3=669.6-ATW;
print'%s %.2f %s'%("\n H3=",H3," kcal/kg")
##h_4-5(ignore bpump work)
h4=72.4;##unit=kcal/kg
##h6 at 27 degree c
h6=27;##unit=kcal/kg
##Turbine steam flow or hot water flow=power output/actual turbine work
TSF=(10*10**6*0.86)/ATW;
print'%s %.2f %s'%("\n Turbine steam flow or hot water flow=",TSF," kg/hr");
##consider cooling water flow  m4:m3*(H3-h4)=m4(h4-h6)
##or
m4=((582.11-72.4)*0.983*10**5)/(72.4-27);
print'%s %.2f %s'%("\n cooling water flow=",m4," kg/hr");
Heat_added=H1-h4
print'%s %.2f %s'%("\n Heat_added=",Heat_added," kcal/kg");
##plant efficiency=Turbine work/Heat added
Plant_efficiency=(ATW/Heat_added);
plant_efficiency=Plant_efficiency*100;
print'%s %.2f %s'%("\n Plant Efficiency=",plant_efficiency," persent");
##Plant heat rate=860/Plant Efficiency
Plant_heat_rate=860./Plant_efficiency;
print'%s %.2f %s'%("\n Plant heat rate=",Plant_heat_rate," kcal/kWh");


##The value of m3=14.03*10^5 is given wrong in the text book;the actual value is m3=11.03*10^5

 Isentropic turbine work= 134.60  kcal/kg

 Actual turbine work= 87.49  kcal/kg

 H3= 582.11  kcal/kg

 Turbine steam flow or hot water flow= 98296.95  kg/hr

 cooling water flow= 1103623.19  kg/hr

 Heat_added= 597.20  kcal/kg

 Plant Efficiency= 14.65  persent

 Plant heat rate= 5870.29  kcal/kWh