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The condensing pressure for a Rankine engine is 1 bar (hf= 417.4 kJ/kg). Calculate the net work for 1 kg/s of steam and the thermal efficiency when the steam at the beginning of expansion is at 50 bar and (a) saturated (b) 350°C and (c) 640°C. Note the variation of efficiency and the quality at the end of the expansion.

The condensing pressure for a Rankine engine is 1 bar (hf= 417.4 kJ/kg). Calculate the net work for 1 kg/s of steam and the thermal efficiency when the steam at the beginning of expansion is at 50 bar and (a) saturated (b) 350°C and (c) 640°C. Note the variation of efficiency and the quality at the end of the expansion.

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
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The condensing pressure for a Rankine engine is 1 bar (hf= 417.4 kJ/kg). Calculate the net work for 1 kg/s of steam and the thermal efficiency when the steam at the beginning of expansion is at 50 bar and (a) saturated (b) 350°C and (c) 640°C. Note the variation of efficiency and the quality at the end of the expansion.

8:35 M l 67 Problem Set on Rankine E... Problem Set on Rankine Engine Problem 1.0 A Rankine turbo-generator unit receives 27,000 kg/h of steam at 1.2 MPa and superheat by 122 degrees. Conden- sate leaves at 22°C. For a brake steam rate of 4.74 kg/kwh, mechanical efficiency of 90% and generator efficiency of 94%, determine (a) the ideal cycle thermal efficiency, (b) the indi- cated engine efficiency, (c) the condition of turbine actual exhaust, and (d) the turbo-generator output in Kw. Ans. (a) 33%, (b) 85.7%, (c) 87%, (d) 5354.5 kw Problem 2.0 The condensing pressure for a Rankine engine is 1 bar. Calculate the net work for 1 kg of steam and the thermal efficiency when the steam at the beginning of expansion is at 50 bar and (a) saturated, (b) 350°C, and (c) 640°C. Ans. (a) 627.2 kJ/kg, 26.4%; (b) 727.3 kJ/kg, 27.5%; (c) 1079.49 kJkg, 32.35% Problem 3.0 There are received 90,000 kg/h of steam at 2.15 MPa, 480°C by a Rankine engine; exhaust occurs at 0.10 MPa. For the engine find (a) W, (b) m, and (c) e, For the cycle find (a) Work net and (b) thermal efficiency ||
Transcribed Image Text:8:35 M l 67 Problem Set on Rankine E... Problem Set on Rankine Engine Problem 1.0 A Rankine turbo-generator unit receives 27,000 kg/h of steam at 1.2 MPa and superheat by 122 degrees. Conden- sate leaves at 22°C. For a brake steam rate of 4.74 kg/kwh, mechanical efficiency of 90% and generator efficiency of 94%, determine (a) the ideal cycle thermal efficiency, (b) the indi- cated engine efficiency, (c) the condition of turbine actual exhaust, and (d) the turbo-generator output in Kw. Ans. (a) 33%, (b) 85.7%, (c) 87%, (d) 5354.5 kw Problem 2.0 The condensing pressure for a Rankine engine is 1 bar. Calculate the net work for 1 kg of steam and the thermal efficiency when the steam at the beginning of expansion is at 50 bar and (a) saturated, (b) 350°C, and (c) 640°C. Ans. (a) 627.2 kJ/kg, 26.4%; (b) 727.3 kJ/kg, 27.5%; (c) 1079.49 kJkg, 32.35% Problem 3.0 There are received 90,000 kg/h of steam at 2.15 MPa, 480°C by a Rankine engine; exhaust occurs at 0.10 MPa. For the engine find (a) W, (b) m, and (c) e, For the cycle find (a) Work net and (b) thermal efficiency ||
Problems Rankine Cycle and Engine 1. In an ideal Rankine cycle, steam is generated at 4.1 MPa and 480°C. The condenser is at 32°C. Determine (a) the ideal pump work, (b) the cycle thermal efficiency, (c) For an engine with the same end states, determine its thermal effi ciency, steam rate, and mep. (d) Considering the engine only, assume the brake engine efficiency to be 78%, the generator efficiency 92%, the steam flow rate 163,600 kg/hg; compute the output of the combined unit. Ans. (a) 4.12 kJ/kg; (b) 38.66%; (c) 38.73%, 2.85 kg/kwh, 51.92 kPa; (d) 41,227 kW 2. A Rankine cycle has the following operating condi- tions: Steam pressure, 2.5MPa Steam temperature, 280°C Exhaust pressure, 0.026 MPa Indicated steam rate, 5.45 kg/kwh Mechanical efficiency, 90% For ideal cycle and engine, calculate (a) the thermal effi• ciency, (b) the engine steam rate), (c) the actual condition of exhaust steam, and(d) the steam flow rate in kg/h for 1 Mw generator output at 94%efficiency. Ans. (a) 28.6%, 28.5%;(b) 4.69 kg/kwh; (c) 86.33%; (d) 6447 kg/h 3. A Rankine turbo-generator unit receives 27,000 kg/h of steam at 1.2 MPa andsuperheat by 122 degrees. Conden sate leaves at 22°C. For a brake steam rate of 4.74 kg/kwh, mechanical efficiency of 90% and generator efficiency of 94%, determine (a) the ideal cycle thermal efficiency. (b) the indi cated enaine efficiency, (c) the condition of turbine actual exhaust, and (d) the turbo-generator output in Kw. Ans. (a) 33'A>, (b) 85.7%, (c) 87%, (d) 5354.5 kw 4. The condensing pressure for a Rankine engine is 1 5. There are received 90,000 kg/h of steam at 2.15 MPa, 480°C by a Rankine engine; exhaust 0<:eurs at 0.10 MPa. For the en,ine find (a) W, (b) m, and (c)•e . For the cycle find (a) t71 th en ne, enters the reheater, and returns at 9 bar, 600°C, expansion then occurs to the condenser pressure of 0.05 bar (h,= 138 kJ/kg) on the basis of flow of 1 kg steam. Find (a) W and e of the cycle (b) W, e and m for the ideal engine (c)In the actual engine the steam enters the reheater at 10 bar, 300°C and later expands to a saturated state at the exhaust to the condenser, find W, e and m. Ans.: (a) 2226.7 kJ/kg, 48.95%; (b) 2246.7 kJ/kg, 49.17%, 1.6 kg;(c)2052.1 kJ/kg, 45.85%, 1.75 kg/kwh. Regenerative Cycle and Engine 11. There are received 68,000 kg/h of steam by an ideal « 0.003.5 MPa (a) For the ideal cycle, find e. (b) A 60,000 kw turbine operates between the same state pointa except that the steam enters the reheat.er at 1.95 MPa and 26CFC, departs at 1.8 MPa and MO°C. The steam flow i, 147,000 41hr. generata efficiency is
Transcribed Image Text:Problems Rankine Cycle and Engine 1. In an ideal Rankine cycle, steam is generated at 4.1 MPa and 480°C. The condenser is at 32°C. Determine (a) the ideal pump work, (b) the cycle thermal efficiency, (c) For an engine with the same end states, determine its thermal effi ciency, steam rate, and mep. (d) Considering the engine only, assume the brake engine efficiency to be 78%, the generator efficiency 92%, the steam flow rate 163,600 kg/hg; compute the output of the combined unit. Ans. (a) 4.12 kJ/kg; (b) 38.66%; (c) 38.73%, 2.85 kg/kwh, 51.92 kPa; (d) 41,227 kW 2. A Rankine cycle has the following operating condi- tions: Steam pressure, 2.5MPa Steam temperature, 280°C Exhaust pressure, 0.026 MPa Indicated steam rate, 5.45 kg/kwh Mechanical efficiency, 90% For ideal cycle and engine, calculate (a) the thermal effi• ciency, (b) the engine steam rate), (c) the actual condition of exhaust steam, and(d) the steam flow rate in kg/h for 1 Mw generator output at 94%efficiency. Ans. (a) 28.6%, 28.5%;(b) 4.69 kg/kwh; (c) 86.33%; (d) 6447 kg/h 3. A Rankine turbo-generator unit receives 27,000 kg/h of steam at 1.2 MPa andsuperheat by 122 degrees. Conden sate leaves at 22°C. For a brake steam rate of 4.74 kg/kwh, mechanical efficiency of 90% and generator efficiency of 94%, determine (a) the ideal cycle thermal efficiency. (b) the indi cated enaine efficiency, (c) the condition of turbine actual exhaust, and (d) the turbo-generator output in Kw. Ans. (a) 33'A>, (b) 85.7%, (c) 87%, (d) 5354.5 kw 4. The condensing pressure for a Rankine engine is 1 5. There are received 90,000 kg/h of steam at 2.15 MPa, 480°C by a Rankine engine; exhaust 0<:eurs at 0.10 MPa. For the en,ine find (a) W, (b) m, and (c)•e . For the cycle find (a) t71 th en ne, enters the reheater, and returns at 9 bar, 600°C, expansion then occurs to the condenser pressure of 0.05 bar (h,= 138 kJ/kg) on the basis of flow of 1 kg steam. Find (a) W and e of the cycle (b) W, e and m for the ideal engine (c)In the actual engine the steam enters the reheater at 10 bar, 300°C and later expands to a saturated state at the exhaust to the condenser, find W, e and m. Ans.: (a) 2226.7 kJ/kg, 48.95%; (b) 2246.7 kJ/kg, 49.17%, 1.6 kg;(c)2052.1 kJ/kg, 45.85%, 1.75 kg/kwh. Regenerative Cycle and Engine 11. There are received 68,000 kg/h of steam by an ideal « 0.003.5 MPa (a) For the ideal cycle, find e. (b) A 60,000 kw turbine operates between the same state pointa except that the steam enters the reheat.er at 1.95 MPa and 26CFC, departs at 1.8 MPa and MO°C. The steam flow i, 147,000 41hr. generata efficiency is
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