工程热力学(英文版)课后题整理后的答案

工程热力学(英文版)课后题整理后的答案内容摘要：

igher temperature medium. 66C A thermalenergy reservoir is a body that can supply or absorb finite quantities of heat isothermally. Some examples are the oceans, the lakes, and the atmosphere. 69C No. Such an engine violates the KelvinPlanck statement of the second law of thermodynamics. 610C Heat engines are cyclic devices that receive heat from a source, convert some of it to work, and reject the rest to a sink. 611C Method (b). With the heating element in the water, heat losses to the surrounding air are minimized, and thus the desired heating can be achieved with less electrical energy input. 613C It is expressed as No heat engine can exchange heat with a single reservoir, 14 and produce an equivalent amount of work. 614C (a) No, (b) Yes. According to the second law, no heat engine can have and efficiency of 100%. 615C No. Such an engine violates the KelvinPlanck statement of the second law of thermodynamics. 616C No. The KelvinPlank limitation applies only to heat engines。 engines that receive heat and convert some of it to work. 629C The difference between the two devices is one of purpose. The purpose of a refrigerator is to remove heat from a cold medium whereas the purpose of a heat pump is to supply heat to a warm medium. 630C The difference between the two devices is one of purpose. The purpose of a refrigerator is to remove heat from a refrigerated space whereas the purpose of an airconditioner is remove heat from a living space. 631C No. Because the refrigerator consumes work to acplish this task. 632C No. Because the heat pump consumes work to acplish this task. 633C The coefficient of performance of a refrigerator represents the amount of heat removed from the refrigerated space for each unit of work supplied. It can be greater than unity. 634C The coefficient of performance of a heat pump represents the amount of heat supplied to the heated space for each unit of work supplied. It can be greater than unity. 635C No. The heat pump captures energy from a cold medium and carries it to a warm medium. It does not create it. 636C No. The refrigerator captures energy from a cold medium and carries it to a warm medium. It does not create it. 637C No device can transfer heat from a cold medium to a warm medium without requiring a heat or work input from the surroundings. 638C The violation of one statement leads to the violation of the other one, as shown in Sec. 64, and thus we conclude that the two statements are equivalent. 658C No. Because it involves heat transfer through a finite temperature difference. 659C Because reversible processes can be approached in reality, and they form the limiting cases. Work producing devices that operate on reversible processes deliver the most work, and work consuming devices that operate on reversible processes consume the least work. 660C When the pression process is nonquasiequilibrium, the molecules before the piston face cannot escape fast enough, forming a high pressure region in front of the piston. It takes more work to move the piston against this high pressure region. 661C When an expansion process is nonquasiequilibrium, the molecules before the piston face cannot follow the piston fast enough, forming a low pressure region behind the piston. The lower pressure that pushes the piston produces less work. 662C The irreversibilities that occur within the system boundaries are internal irreversibilities。 those which occur outside the system boundaries are external irreversibilities. 663C A reversible expansion or pression process cannot involve unrestrained 15 expansion or sudden pression, and thus it is quasiequilibrium. A quasiequilibrium expansion or pression process, on the other hand, may involve external irreversibilities (such as heat transfer through a finite temperature difference), and thus is not necessarily reversible. 664C The four processes that make up the Carnot cycle are isothermal expansion, reversible adiabatic expansion, isothermal pression, and reversible adiabatic pression. 665C They are (1) the thermal efficiency of an irreversible heat engine is lower than the efficiency of a reversible heat engine operating between the same two reservoirs, and (2) the thermal efficiency of all the reversible heat engines operating between the same two reservoirs are equal. 666C False. The second Carnot principle states that no heat engine cycle can have a higher thermal efficiency than the Carnot cycle operating between the same temperature limits. 667C Yes. The second Carnot principle states that all reversible heat engine cycles operating between the same temperature limits have the same thermal efficiency. 668C (a) No, (b) No. They would violate the Carnot principle. 669C No. 670C The one that has a source temperature of 600176。 C. This is true because the higher the temperature at which heat is supplied to the working fluid of a heat engine, the higher the thermal efficiency. 681C By increasing TL or by decreasing TH. 682C It is the COP that a Carnot refrigerator would have, 683C No. At best (when everything is reversible), the increase in the work produced will be equal to the work consumed by the refrigerator. In reality, the work consumed by the refrigerator will always be greater than the additional work produced, resulting in a decrease in the thermal efficiency of the power plant. 第七章 71C Yes. Because we used the relation (QH/TH) = (QL/TL) in the proof, which is the defining relation of absolute temperature. 72C No. The ∫δ Q represents the heat transfer during a cycle, which could be positive. 16 76C The entropy change will be the same for both cases since entropy is a property and it has a fixed value at a fixed state. 77C No. In general, that integral will have a different value for diffe。