Question

5. A binary geothermal power plant in CA has brine coming out of the ground at 280 °F and loses its energy to freon in a tube and shell heat exchanger resulting in the brine temperature reducing to 110 °F. The brine flow rate is 5 x 10 lb/h. The Freon-12 leaves the tube and shell heat exchanger at 230 °F/577 psia. It expands in a turbine to 128.24 psia with a polytropic efficiency of 0.70. The work of the pump is 1.616 Btu/lbo, Determine the mass flow rate of the Freon-12. (23 pts) hat 128.24 psia = 30.619 Btu/Ibm, assume brine is hat 280 °F and 110 °E, respectively.

Answer 1

Brine Thi = 280 f = 137.78°C. Tb2 = 11000 = 43.33°C. m = 57106 dblus = 625.99 kg/s. freen - R12 To =230°F = 1100c. P32577 psia = 3.978 mpa. Pq = 128.24 pia 20.884 MPa Work done by pump Wp a p. 616 Btu/k = 3.758 kJlby. Wp = ha-hi

on his he at 128-24 psia (0.884 mph) = 30.619 Bluline = 71.1988 killeg. .: 3-758= har 71.1988 e has 74.77 kJ/kg According to conservation of energy, Heat lost by beine & heat gained by Fron in mg (hay-bbg) = ing Cha-ha) ha = he at 250°F = 576.3 kJ/kg hbaz he at 1100r = 180. 1 kolleg ha = hg at 23% and 577 psia = 196.484 killeg) .629.99 (576.3-180.)) = f ( 196.484-74.77) wilde ime = 2047.96 kegls = 1.625% 107 lb/hs

Table A.2.1 (Contd.) FREON-TABLE P. hug s 1 1 1 1 1 1 0.0807 0.1004 0.1237 0.1509 0.1826 0.2191 0.2610 0.3086 0.3626 0.4233 0.4914 0.5673 0.6516 0.7449 0.8477 0.9607 1.0843 1.2193 1.3663 1.5259 1.6988 1.8858 2.0874 2.3046 2.5380 2.7885 3.0569 3.3440 3.6509 3.9784 0.666 0.672 0.679 0.685 0.693 0.700 0.708 0.716 0.724 0.733 0.743 0.752 0.763 0.774 0.786 0.798 0.811 0.826 0.841 0.858 0.877 0.897 0.920 0.946 0.976 1.012 1.056 1.113 1.197 1.364 0.195398 0.159375 0.131166 0.108847 0.091018 0.076646 0.064963 0.055389 0.047485 0.040914 0.035413 0.030780 0.026854 0.023508 0.020641 0.018171 0.016032 0.014170 0.012542 0.01111 0.009847 0.008725 0.007723 0.006821 0.006005 0.005258 0.004563 0.003903 0.003242 0.002462 4.416 8.854 13.315 17.800 22.312 26.851 31.420 36.022 40.659 45.337 50.058 54.828 59.653 64.539 69.494 74.527 79.647 84.868 90.201 95.665 101.279 107.067 113.058 119.291 125.818 132.708 140.068 148.076 157.085 168.059 167.368 165.222 163.037 160.810 158.534 156.207 153.823 151.376 148.859 146.265 143.586 140.812 137.933 134.936 131.805 128.525 125.074 121.430 117.565 113.443 109.024 104.255 99.068 93.373 87.047 79.907 71.658 61.768 49.014 28.425 171.784 174.076 176.352 178.610 180.846 183.058 185.243 187.397 189.518 191.602 193.644 195.641 197386 199.475 201.299 203.051 204.722 206.298 207.766 209.109 210.303 211.321 212.126 212.665 212.865 212.614 211.726 209.843 206.099 196.484 0.0187 0.0371 0.0552 0.0730 0.0906 0.1079 0.1250 0.1418 0.1585 0.1750 0.1914 0.2076 0.2237 0.2397 0.2557 0.2716 0.2875 0.3034 0.3194 0.3355 0.3518 0.3683 0.3851 0.4023 0.4201 0.4385 0.4579 0.4788 0.5023 0.5322 0.7214 0.7165 0.7121 0.7082 0.7046 0.7014 0.6986 0.6960 0.6937 0.6916 0.6897 0.6879 0.6863 0.6848 0.6834 0.6820 0.6806 0.6792 0.6777 0.6760 0.6742 0.6721 0.6697 0.6667 0.6631 0.6585 0.6526 0.6444 0.6319 0.6064 95 100 105 110