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4.1 Calculate the minimum work required to produce 10 kg ice cubes from water initially at 273 K. Assume that the surroundings are at 300 K. The latent heat of fusion of water at 273 K = 333.5 kJ/kg.

4.1 Calculate the minimum work required to produce 10 kg ice cubes from water initially at 273 K. Assume that the surroundings are at 300 K. The latent heat of fusion of water at 273 K = 333.5 kJ/kg.

Introduction to Chemical Engineering Thermodynamics
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Jio 4G VOLTE 46,ll Šil 0.00K/s J 53I 18:11 Emergency calls only A_Textbook_ofC... process". Do you agree? 20. How would the increase in entropy be used as a measure of the irreversibility of a process? 21. How is the entropy and probability interrelated? 22. “A knowledge of the entropy change provides information concerning the structural changes accompanying a process". Comment on this. 23. State the third law of thermodynamics. How does it follow from the statistical explanation for entropy? EXERCISES 4.1 Calculate the minimum work required to produce 10 kg ice cubes from water initially at 273 K. Assume that the surroundings are at 300 K. The latent heat of fusion of water at 273 K = 333.5 kJ/kg. 4.2 A 800 MW thermal power plant uses steam at 600 K and discards heat to a river at 295 K. Determine the heat discarded to the river if the thermal efficiency of the plant is 70 per cent of the maximum possible value. 4.3 The overhead vapour from a distillation column is taken to a condenser where it is condensed by heat exchange with cooling water that enters at 300 K and leaves at 310 K. The vapour can be treated as pure water vapour at 101.3 kPa. Its flow rate is 5000 kg/h. It is condensed and subcooled to 345 K. If the condenser were replaced by a reversible engine calculate the following: (a) The work output of the engine (b) The per cent reduction in the cooling water circulation rate when the condenser is replaced with Carnot engine. 4.4 A reversible refrigerator absorbs heat from water at 273K in order to produce ice at the same temperature and rejects heat to the surroundings at 300 K. The work requirement of the refrigerator is to be met by a reversible heat engine operating between a heat source at 425 K and surroundings at 300 K. For each kilo joule of heat received by the engine, calculate: (a) The heat removed from water (b) The heat rejected to the surroundings. 4.5 An inventor claims to have developed a heat pump with a COP of 6 which maintains the cold space at 250 K when operating in a surrounding temperature of 310 K. Would you agree with his claim? 4.6 An engine using hot spring water at 330 K as the heat source receives 420 kJ and is said to reject 335 kJ to melting ice at 273 K. Comment on the engine efficiency. 4.7 An inventor claims to have developed a refrigerating machine which maintains the refrigerated space at 267 K while operating in a room at 300 K. If the COP claimed is 8.5, how would you evaluate his claim? 4.8 One mole of an ideal gas is compressed isothermally at 400 K from an initial pressure of 1 bar to a final pressure of 10 bar. The work required for this irreversible process is 20 per cent more than that required for a reversible compression. The heat liberated during compression is absorbed by a heat reservoir at 300 K. Determine: (a) The entropy change of the gas (b) The entropy change of the reservoir (c) The total entropy change. 4.9 Three moles hydrogen and 1 mol nitrogen, both at 10 bar and 373 K are separately admitted, mixed and then heated to 773 K in a heat exchanger with a corresponding increase in pressure. Calculate the entropy change in the process. Assume Cy=21 J/mol K for the mixture. 4.10 Ten kilogram of water (the system) is heated from 290 K to 340 K under the following conditions: (a) Using saturated steam at 10 bar (b) Using saturated steam at 5 bar (c) Using superheated steam at 5 bar and 513 K (d) Using 10 kg water at 340 K in a counter-current exchanger. Assume that the condensate is not subcooled. In each case calculate the entropy change of the system, the entropy change of the surroundings and the total entropy change and compare them. 4.11 An ideal gas at 300 K and 10 bar enters an apparatus, which is thermally and mechanically insulated from the surroundings. The gas leaves the apparatus in two streams in equal quantities. One stream is at 360 K and 1 bar and the other is at 240 K and 1 bar. The heat capacity of the
Transcribed Image Text:Jio 4G VOLTE 46,ll Šil 0.00K/s J 53I 18:11 Emergency calls only A_Textbook_ofC... process". Do you agree? 20. How would the increase in entropy be used as a measure of the irreversibility of a process? 21. How is the entropy and probability interrelated? 22. “A knowledge of the entropy change provides information concerning the structural changes accompanying a process". Comment on this. 23. State the third law of thermodynamics. How does it follow from the statistical explanation for entropy? EXERCISES 4.1 Calculate the minimum work required to produce 10 kg ice cubes from water initially at 273 K. Assume that the surroundings are at 300 K. The latent heat of fusion of water at 273 K = 333.5 kJ/kg. 4.2 A 800 MW thermal power plant uses steam at 600 K and discards heat to a river at 295 K. Determine the heat discarded to the river if the thermal efficiency of the plant is 70 per cent of the maximum possible value. 4.3 The overhead vapour from a distillation column is taken to a condenser where it is condensed by heat exchange with cooling water that enters at 300 K and leaves at 310 K. The vapour can be treated as pure water vapour at 101.3 kPa. Its flow rate is 5000 kg/h. It is condensed and subcooled to 345 K. If the condenser were replaced by a reversible engine calculate the following: (a) The work output of the engine (b) The per cent reduction in the cooling water circulation rate when the condenser is replaced with Carnot engine. 4.4 A reversible refrigerator absorbs heat from water at 273K in order to produce ice at the same temperature and rejects heat to the surroundings at 300 K. The work requirement of the refrigerator is to be met by a reversible heat engine operating between a heat source at 425 K and surroundings at 300 K. For each kilo joule of heat received by the engine, calculate: (a) The heat removed from water (b) The heat rejected to the surroundings. 4.5 An inventor claims to have developed a heat pump with a COP of 6 which maintains the cold space at 250 K when operating in a surrounding temperature of 310 K. Would you agree with his claim? 4.6 An engine using hot spring water at 330 K as the heat source receives 420 kJ and is said to reject 335 kJ to melting ice at 273 K. Comment on the engine efficiency. 4.7 An inventor claims to have developed a refrigerating machine which maintains the refrigerated space at 267 K while operating in a room at 300 K. If the COP claimed is 8.5, how would you evaluate his claim? 4.8 One mole of an ideal gas is compressed isothermally at 400 K from an initial pressure of 1 bar to a final pressure of 10 bar. The work required for this irreversible process is 20 per cent more than that required for a reversible compression. The heat liberated during compression is absorbed by a heat reservoir at 300 K. Determine: (a) The entropy change of the gas (b) The entropy change of the reservoir (c) The total entropy change. 4.9 Three moles hydrogen and 1 mol nitrogen, both at 10 bar and 373 K are separately admitted, mixed and then heated to 773 K in a heat exchanger with a corresponding increase in pressure. Calculate the entropy change in the process. Assume Cy=21 J/mol K for the mixture. 4.10 Ten kilogram of water (the system) is heated from 290 K to 340 K under the following conditions: (a) Using saturated steam at 10 bar (b) Using saturated steam at 5 bar (c) Using superheated steam at 5 bar and 513 K (d) Using 10 kg water at 340 K in a counter-current exchanger. Assume that the condensate is not subcooled. In each case calculate the entropy change of the system, the entropy change of the surroundings and the total entropy change and compare them. 4.11 An ideal gas at 300 K and 10 bar enters an apparatus, which is thermally and mechanically insulated from the surroundings. The gas leaves the apparatus in two streams in equal quantities. One stream is at 360 K and 1 bar and the other is at 240 K and 1 bar. The heat capacity of the
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