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refrigerator with tetrafluoroethane as refrigerant operates with an evaporation temperature of −25°C and a condensation temperature of 26°C. Saturated liquid refrigerant from the condenser flows through an expansion valve into the evaporator, from which it emerges as saturated vapor. (a) For a cooling rate of 5 kJ·s−1, what is the circulation rate of the refrigerant? (b) By how much would the circulation rate be reduced if the throttle valve were replaced by a turbine in which the refrigerant expands isentropically?

refrigerator with tetrafluoroethane as refrigerant operates with an evaporation temperature of −25°C and a condensation temperature of 26°C. Saturated liquid refrigerant from the condenser flows through an expansion valve into the evaporator, from which it emerges as saturated vapor. (a) For a cooling rate of 5 kJ·s−1, what is the circulation rate of the refrigerant? (b) By how much would the circulation rate be reduced if the throttle valve were replaced by a turbine in which the refrigerant expands isentropically?

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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A refrigerator with tetrafluoroethane as refrigerant operates with an evaporation temperature of −25°C and a condensation temperature of 26°C. Saturated liquid refrigerant from the condenser flows through an expansion valve into the evaporator, from which it emerges as saturated vapor.

(a) For a cooling rate of 5 kJ·s−1, what is the circulation rate of the refrigerant?

(b) By how much would the circulation rate be reduced if the throttle valve were replaced by a turbine in which the refrigerant expands isentropically?

 

 

9.3. The Choice of Refrigerant 333 Table 9.1: Properties of Saturated 1,1,1,2-Tetrafluoroethane (R134A)* 100 20. 200 550 150 250 300 350 400 450 500 600 20. Volume Enthalpy kJ-kg-1 Entropy kJ-kg-1.K-1 R-134a (1.1.1.2 tetrafluoroethane) - s00. kg/m3 400. m³.kg-1 250 700. 1000- 600. 900 800 reference state: h= 200.0 kJ/kg, s 1.00 kJka K) for saturated liquid at OC 10. 10. T(°C) Р bar) H SV 8. 300 8. -40 0.512 0.000705 0.361080 148.14 374.00 377,17 380.32 0.796 1.764 6. i.. ..! 6. 0.000713 0.000720 -35 0.661 0.844 1.064 1.327 0.284020 154.44 0.822 1.758 1.752 1.746 1.741 A200. 0.225940 0.181620 0.147390 160,79 167.19 173.64 -30 0.849 0.875 0.900 150. 4. 4. 383.45 386.55 -25 0.000728 0.000736 100. -20 80 80. 1.446 1.573 1.708 1.852 2.006 176.23 178,83 181.44 184.07 186.70 0.000740 0.000743 0.135920 0.125510 0.116050 0.107440 -18 -16 387,79 389.02 0.910 0.921 0.931 0.941 0.951 1.740 1.738 1.736 1.735 1.733 2. 70 60. 2. 60 -14 0.000746 390.24 40. 50 -12 -10 0.000750 391.46 30. 1. 40 1. 0.000754 0.099590 392.66 0.8 30 20. 0.8 0.092422 0.085867 0.079866 -8 2.169 0.000757 189.34 393.87 0.961 1.732 1.731 1.729 0.6 0.6 2.343 2.527 2.722 2.928 -6 -4 0.000761 0.000765 0.000768 191.99 194.65 395.06 396.25 397.43 0.971 0.980 0.990 1.000 15. 0.4 0.4 197.32 200.00 -2 0.074362 1.728 10. 0.000772 0.069309 398.60 1.727 8.0 3.146 0.000776 0,064663 202.69 399.77 1.010 1.726 6.0 0.2 T=-10 C 0.2 4 3.377 0.000780 0.060385 205.40 400.92 1.020 1,725 4.0 6 8 3.620 3.876 4.146 0.000785 0.000789 0.056443 0.052804 208.11 210.84 213.58 402.06 403.20 1.029 1.039 1.049 1.724 1.723 1.722 3.0 10 0.000793 0.049442 404.32 0.1 0.1 23 E-30 0.08 0.08 2.0 4.430 4.729 5.043 5.372 5.717 12 0.000797 0.046332 216.33 405.43 1.058 1.721 0.06 0.06 1.720 1.720 1.719 1.718 1.5 406.53 407.61 408.69 409.75 14 0.000802 0.043451 219.09 1.068 -40 221.87 224.66 227.47 1.077 1.087 1.096 16 0.000807 0.040780 0.04 1.0 0.04 18 20 0.000811 0.000816 0.038301 0.035997 -50 0.80 0.60 22 0.033854 0.031858 6.079 6.458 6.854 7.269 7.702 0.000821 0.000826 230.29 233.12 235.97 238.84 241.72 410.79 411.82 412.84 413.84 414.82 1.106 1.115 1.125 1.134 1.144 1.717 1.717 0.02 0.02 24 0.40 0.000831 0.000837 0.000842 26 0.029998 1.716 0.028263 0.026642 1.715 1.715 28 0.01 100 0.01 600 30 150 200 250 300 350 400 450 500 550 417.19 419.43 421.52 423.44 1.167 1.191 1.214 35 8.870 0.000857 0.023033 249.01 1.713 Enthalpy (kJ/kg) 40 45 10.166 11.599 0.000872 0.000889 0.019966 256.41 263.94 1.711 1.709 Retrieved from: Green, Don W., and Perry, Robert H. Perry's Chemical Engineers' Handbook (8th Edition). Blacklick, OH, USA: McGraw-Hill Professional Publishing, 2007. Copyright © 2007. McGraw-Hill Professional Publishing. All rights reserved. 0.017344 0.000907 0.000927 50 13.179 14.915 0.015089 271.62 1.238 1.70 55 0.013140 279.47 425.15 1.261 1.705 Figure F.2 PH diagram for tetrafluoroethane (HFC-134a). 16.818 18.898 0.000950 0.011444 426.63 427.82 428.65 429.03 60 287.50 295.76 304.28 313.13 1.285 1.309 1.702 65 0.000975 0.009960 1.699 70 75 21.168 0.001004 0.001037 0.008653 0.007491 1.333 1.358 1.384 1.696 1.691 23.641 80 26.332 0.001077 0.006448 322.39 428.81 1.685 i Ospi +00pi 0ɛ 000 1100. 1050. Pressure (MPa)
Transcribed Image Text:9.3. The Choice of Refrigerant 333 Table 9.1: Properties of Saturated 1,1,1,2-Tetrafluoroethane (R134A)* 100 20. 200 550 150 250 300 350 400 450 500 600 20. Volume Enthalpy kJ-kg-1 Entropy kJ-kg-1.K-1 R-134a (1.1.1.2 tetrafluoroethane) - s00. kg/m3 400. m³.kg-1 250 700. 1000- 600. 900 800 reference state: h= 200.0 kJ/kg, s 1.00 kJka K) for saturated liquid at OC 10. 10. T(°C) Р bar) H SV 8. 300 8. -40 0.512 0.000705 0.361080 148.14 374.00 377,17 380.32 0.796 1.764 6. i.. ..! 6. 0.000713 0.000720 -35 0.661 0.844 1.064 1.327 0.284020 154.44 0.822 1.758 1.752 1.746 1.741 A200. 0.225940 0.181620 0.147390 160,79 167.19 173.64 -30 0.849 0.875 0.900 150. 4. 4. 383.45 386.55 -25 0.000728 0.000736 100. -20 80 80. 1.446 1.573 1.708 1.852 2.006 176.23 178,83 181.44 184.07 186.70 0.000740 0.000743 0.135920 0.125510 0.116050 0.107440 -18 -16 387,79 389.02 0.910 0.921 0.931 0.941 0.951 1.740 1.738 1.736 1.735 1.733 2. 70 60. 2. 60 -14 0.000746 390.24 40. 50 -12 -10 0.000750 391.46 30. 1. 40 1. 0.000754 0.099590 392.66 0.8 30 20. 0.8 0.092422 0.085867 0.079866 -8 2.169 0.000757 189.34 393.87 0.961 1.732 1.731 1.729 0.6 0.6 2.343 2.527 2.722 2.928 -6 -4 0.000761 0.000765 0.000768 191.99 194.65 395.06 396.25 397.43 0.971 0.980 0.990 1.000 15. 0.4 0.4 197.32 200.00 -2 0.074362 1.728 10. 0.000772 0.069309 398.60 1.727 8.0 3.146 0.000776 0,064663 202.69 399.77 1.010 1.726 6.0 0.2 T=-10 C 0.2 4 3.377 0.000780 0.060385 205.40 400.92 1.020 1,725 4.0 6 8 3.620 3.876 4.146 0.000785 0.000789 0.056443 0.052804 208.11 210.84 213.58 402.06 403.20 1.029 1.039 1.049 1.724 1.723 1.722 3.0 10 0.000793 0.049442 404.32 0.1 0.1 23 E-30 0.08 0.08 2.0 4.430 4.729 5.043 5.372 5.717 12 0.000797 0.046332 216.33 405.43 1.058 1.721 0.06 0.06 1.720 1.720 1.719 1.718 1.5 406.53 407.61 408.69 409.75 14 0.000802 0.043451 219.09 1.068 -40 221.87 224.66 227.47 1.077 1.087 1.096 16 0.000807 0.040780 0.04 1.0 0.04 18 20 0.000811 0.000816 0.038301 0.035997 -50 0.80 0.60 22 0.033854 0.031858 6.079 6.458 6.854 7.269 7.702 0.000821 0.000826 230.29 233.12 235.97 238.84 241.72 410.79 411.82 412.84 413.84 414.82 1.106 1.115 1.125 1.134 1.144 1.717 1.717 0.02 0.02 24 0.40 0.000831 0.000837 0.000842 26 0.029998 1.716 0.028263 0.026642 1.715 1.715 28 0.01 100 0.01 600 30 150 200 250 300 350 400 450 500 550 417.19 419.43 421.52 423.44 1.167 1.191 1.214 35 8.870 0.000857 0.023033 249.01 1.713 Enthalpy (kJ/kg) 40 45 10.166 11.599 0.000872 0.000889 0.019966 256.41 263.94 1.711 1.709 Retrieved from: Green, Don W., and Perry, Robert H. Perry's Chemical Engineers' Handbook (8th Edition). Blacklick, OH, USA: McGraw-Hill Professional Publishing, 2007. Copyright © 2007. McGraw-Hill Professional Publishing. All rights reserved. 0.017344 0.000907 0.000927 50 13.179 14.915 0.015089 271.62 1.238 1.70 55 0.013140 279.47 425.15 1.261 1.705 Figure F.2 PH diagram for tetrafluoroethane (HFC-134a). 16.818 18.898 0.000950 0.011444 426.63 427.82 428.65 429.03 60 287.50 295.76 304.28 313.13 1.285 1.309 1.702 65 0.000975 0.009960 1.699 70 75 21.168 0.001004 0.001037 0.008653 0.007491 1.333 1.358 1.384 1.696 1.691 23.641 80 26.332 0.001077 0.006448 322.39 428.81 1.685 i Ospi +00pi 0ɛ 000 1100. 1050. Pressure (MPa)
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