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Suppose an old power plant uses steam turbines to produce 0.5 GW (5 x 10° W) of electricity. The turbines take in steam at a temperature of 600°C, and waste heat is expelled into the environment at 30°C. (a) If the plant operates at its maximum efficiency, at what rate does it expel its waste heat into the environment? Assume the cold reservoir for this plant is a river whose flow rate is 80 m³/s. By how much will (b) the temperature of the river increase due to the waste heat expelled by the plant? (c) environment), the plant could instead be cooled by evaporating river water. At what rate would the To avoid increasing the temperature of the river water (which may be harmful to the water have to be evaporated to cool the plant, assuming the latent heat to evaporate water at the relevant temperature is 2400 J/g?

Suppose an old power plant uses steam turbines to produce 0.5 GW (5 x 10° W) of electricity. The turbines take in steam at a temperature of 600°C, and waste heat is expelled into the environment at 30°C. (a) If the plant operates at its maximum efficiency, at what rate does it expel its waste heat into the environment? Assume the cold reservoir for this plant is a river whose flow rate is 80 m³/s. By how much will (b) the temperature of the river increase due to the waste heat expelled by the plant? (c) environment), the plant could instead be cooled by evaporating river water. At what rate would the To avoid increasing the temperature of the river water (which may be harmful to the water have to be evaporated to cool the plant, assuming the latent heat to evaporate water at the relevant temperature is 2400 J/g?

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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Swater Ssteam Hwater (kJ) T' Hsteam (°C) (bar) (kJ) (kJ/K) (kJ/K) 0.006 2501 9.156 10 0.012 42 2520 0.151 8.901 20 0.023 84 2538 0.297 8.667 30 0.042 126 2556 0.437 8.453 50 0.123 209 2592 0.704 8.076 100 1.013 419 2676 1.307 7.355 Table 4.1. Properties of saturated water/steam. Pressures are given in bars, where 1 bar = 10° Pa a 1 atm. All values are for 1 kg of fluid, and are measured relative to liquid water at the triple point (0.01°C and 0.006 bar). Excerpted from Keenan et al. (1978). Temperature (°C) P (bar) 200 300 400 500 600 H (kJ) S (kJ/K) H (kJ) S (kJ/K) H (kJ) S (kJ/K) H (kJ) S (kJ/K) H (kJ) S (kJ/K) H (kJ) S (kJ/K) 1.0 2875 3074 3278 3488 3705 7.834 8.216 8.544 8.834 9.098 3.0 2866 3069 3275 3486 3703 7.312 7.702 8.033 8.325 8.589 10 2828 3051 3264 3479 3698 6.694 7.123 7.465 7.762 8.029 30 2994 3231 3457 3682 6.539 6.921 7.234 7.509 100 3097 3374 3625 6.212 6.597 6.903 300 2151 3081 3444 4.473 5.791 6.233 Table 4.2. Properties of superheated steam. All values are for 1 kg of fluid, and are measured relative to liquid water at the triple point. Excerpted from Keenan et al. (1978).
Transcribed Image Text:Swater Ssteam Hwater (kJ) T' Hsteam (°C) (bar) (kJ) (kJ/K) (kJ/K) 0.006 2501 9.156 10 0.012 42 2520 0.151 8.901 20 0.023 84 2538 0.297 8.667 30 0.042 126 2556 0.437 8.453 50 0.123 209 2592 0.704 8.076 100 1.013 419 2676 1.307 7.355 Table 4.1. Properties of saturated water/steam. Pressures are given in bars, where 1 bar = 10° Pa a 1 atm. All values are for 1 kg of fluid, and are measured relative to liquid water at the triple point (0.01°C and 0.006 bar). Excerpted from Keenan et al. (1978). Temperature (°C) P (bar) 200 300 400 500 600 H (kJ) S (kJ/K) H (kJ) S (kJ/K) H (kJ) S (kJ/K) H (kJ) S (kJ/K) H (kJ) S (kJ/K) H (kJ) S (kJ/K) 1.0 2875 3074 3278 3488 3705 7.834 8.216 8.544 8.834 9.098 3.0 2866 3069 3275 3486 3703 7.312 7.702 8.033 8.325 8.589 10 2828 3051 3264 3479 3698 6.694 7.123 7.465 7.762 8.029 30 2994 3231 3457 3682 6.539 6.921 7.234 7.509 100 3097 3374 3625 6.212 6.597 6.903 300 2151 3081 3444 4.473 5.791 6.233 Table 4.2. Properties of superheated steam. All values are for 1 kg of fluid, and are measured relative to liquid water at the triple point. Excerpted from Keenan et al. (1978).
Suppose an old power plant uses steam turbines to produce 0.5 GW (5 x 108 W) of electricity. The turbines take in steam at a temperature of 600°C, and waste heat is expelled into the environment at 30°C. (a) If the plant operates at its maximum efficiency, at what rate does it expel its waste heat into the environment? Assume the cold reservoir for this plant is a river whose flow rate is 80 m³/s. By how much will (b) the temperature of the river increase due to the waste heat expelled by the plant? (c) environment), the plant could instead be cooled by evaporating river water. At what rate would the To avoid increasing the temperature of the river water (which may be harmful to the water have to be evaporated to cool the plant, assuming the latent heat to evaporate water at the relevant temperature is 2400 J/g? If the plant is upgraded such that the turbines take in steam at 650°C, and the plant operates at (d) its maximum possible efficiency, how much additional power is generated as a result of the upgrade? (e) the maximum steam pressure is 10 bars, and the plant executes a Rankine Cycle rather than functioning Now suppose the plant operates with a maximum steam temperature of only 300°C. Supposing like an ideal engine, find the efficiency of the plant. [Hint: use Tables 4.1 and 4.2 in the textbook.]
Transcribed Image Text:Suppose an old power plant uses steam turbines to produce 0.5 GW (5 x 108 W) of electricity. The turbines take in steam at a temperature of 600°C, and waste heat is expelled into the environment at 30°C. (a) If the plant operates at its maximum efficiency, at what rate does it expel its waste heat into the environment? Assume the cold reservoir for this plant is a river whose flow rate is 80 m³/s. By how much will (b) the temperature of the river increase due to the waste heat expelled by the plant? (c) environment), the plant could instead be cooled by evaporating river water. At what rate would the To avoid increasing the temperature of the river water (which may be harmful to the water have to be evaporated to cool the plant, assuming the latent heat to evaporate water at the relevant temperature is 2400 J/g? If the plant is upgraded such that the turbines take in steam at 650°C, and the plant operates at (d) its maximum possible efficiency, how much additional power is generated as a result of the upgrade? (e) the maximum steam pressure is 10 bars, and the plant executes a Rankine Cycle rather than functioning Now suppose the plant operates with a maximum steam temperature of only 300°C. Supposing like an ideal engine, find the efficiency of the plant. [Hint: use Tables 4.1 and 4.2 in the textbook.]
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