Chapter 7, Problem 7.42CU

A balloon filled with helium at 20°C, 1 bar and a volume of 0.5 m³ is moving with a velocity of 15 m/s at an elevation of 0.5 km relative to an exergy reference environment for which To = 20°C, po = 1 bar. Using the ideal gas model with k = 1.67, determine the specific exergy of the helium, in kJ.

If a closed system undergoes a process for which S2=S1, the process must be internally reversible. - True or False One of the Carnot principles states that all power cycles operating between the same two thermal reservoirs have the same thermal efficiency. - True or False One statement of the second law of thermodynamics recognizes that the extensive property entropy is produced within systems whenever internal irreversibilities are present. - True or False

Four kilograms of a two-phase liquid-vapor mixture of water initially at 300°C and x1= 0.3 undergo the two different processes described below. In each case, the mixture is brought from the initial state to a saturated vapor state, while the volume remains constant. For each process, determine the change in exergy of the water, the net amounts of exergy transfer by work and heat, and the amount of exergy destruction, each in kJ. Let To = 300K, po 1 bar, and ignore the effects of motion and gravity. Comment on the difference between the exergy destruction values. a. The process is brought about adiabatically by stirring the mixture with a paddle wheel.

Four kilograms of a two-phase liquid-vapor mixture of water initially at 300°C and x1= 0.3 undergo the two different processes described below. In each case, the mixture is brought from the initial state to a saturated vapor state, while the volume remains constant. For each process, determine the change in exergy of the water, the net amounts of exergy transfer by work and heat, and the amount of exergy destruction, each in kJ. Let To = 300K, po 1 bar, and ignore the effects of motion and gravity. Comment on the difference between the exergy destruction values. a. The process is brought about adiabatically by stirring the mixture with a paddle wheel. b. The process is brought about by heat transfer from a thermal reservoir at 610 K. The temperature of the water at the location where the heat transfer occurs is 610 K.

Four kilograms of a two-phase liquid-vapor mixture of water initially at 300°C and x, = 0.5 undergo the two different processes 7.33 described below. In each case, the mixture is brought from the initial state to a saturated vapor state, while the volume remains constant. For each process, determine the change in exergy of the water, the net amounts of exergy transfer by work and heat, and the amount of exergy destruction, each in kJ. Let To = 300 K, Po =1 bar, and ignore the effects of motion and gravity. Comment on the difference between the exergy destruction values. a. The process is brought about adiabatically by stirring the mixture with a paddle wheel. Answer b. The process is brought about by heat transfer from a thermal reservoir at 610 K. The temperature of the water at the location where the heat transfer occurs is 610 K Answer

7.27 Figure P7.27 provides steady-state data for the outer wall of a dwelling on a day when the indoor temperature is maintained at 25°C and the outdoor temperature is 35°C. The heat transfer rate through the wall is 1000 W. Determine, in W, the rate of exergy destruction (a) within the wall, and (b) within the enlarged system shown on the figure by the dashed line. Comment. Let T₂ = 35°C. 20.13, 33-56 Indoor Boundary of enlarged- temperature=25°C T=27C T-3C FIGURE PLAT Outdoor temperature=35°C

answer 99 and 100

A domestic water heater holds 189 L of water at 60°C, 1 atm. Determine the exergy of the hot water, in kJ. To what elevation, in m, would a 1000-kg mass have to be raised from zero elevation relative to the reference environment for its exergy to equal that of the hot water? Let To = 298 K, po = 1 atm, g = 9.81 m/s².

Thermodynamics, please help and show all work please.