Chapter 7, Problem 7.30CU

If the specific exergy of a gas in a cylinder of an internal combustion engine modeled as air behaving like an ideal gas is 368.91 kJ / kg and the cylinder contains 2450 cm2 of gaseous combustion products. Åt what elevation in meters 3-kg mass does it have to be lifted from zero elevation with respect to the reference environment so that its exergy equals the exergy of the cylinder? Assume gravity as g = 9.81 m /s^2 NOTE: The density of dry air at a pressure of 7 bar and a temperature of 867 ° C is 2.1388 kg / m^3.

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.

7.36 At steady state, hot gaseous products of combustion from a gas turbine cool from 3000°F to 250°F as they flow through a pipe. Owing to negligible fluid friction, the flow occurs at nearly constant pressure. Applying the ideal gas model with ₂ = 0.3 Btu/lb/ºR, determine the exergy transfer accompanying heat transfer from the gas, in Btu per lb of gas flowing. Let T. = 80°F and ignore the effects of motion and gravity. -568.43

At steady state, an electric pump motor develops power along its output shaft of 0.7 hp whiledrawing 6 amps at 100 V. The outer surface of the motor is at 150°F. Let T = 40°F.Determine: (a) the magnitude of the rate of heat transfer leaving the motor, in Btu/h.(b) the exergy flow with input power, exergy flow with output power, magnitude of exergy flowwith heat transfer leaving the motor, and exergy destruction, all in Btu/h.

Using image below Evaluate the exergy X1 of the initial state 1 and answer the following question: • Is the useful work in the process 1 → 2 → DS smaller, equal, or greater than exergy X1? • Discuss your result

13. Determine: a. the magnitude of the process heat production rate, in Btu/h b. the magnitude of the rate of exergy output, in Btu/h, as net work. c. the rate of exergy transfer, in Btu/h, to the working fluid passing through the steam generator. d. the magnitude of the rateof exergy output, in Btu/h, with the process heat. e. the magnitude of the rate of exergy loss, in Btu/h, from the working fluid passing through the condenser f. the sun of the rate of energy destrution, in Btu/h, in the turbine, process heat exchager, trap, and pump.

Thermodynamics. 1) For a closed system, as the exergy reference environment temperature ___________, the exergy destruction rate decreases 2) Which of the following statements does not describe the exergy reference environment? It is large in extent. It has a uniform temperature. It is incompressible. It has a uniform pressure.   3) Air within a piston–cylinder assembly undergoes an expansion process from an initial volume of 0.5 m3 to 1 m3. The dead state pressure is 100 kPa. If the work associated with the process is 60 kJ, determine the exergy transfer accompanying work, in kJ.

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 for its exergy to equal that of the hot water? Let T0 = 298 K, p0 = 1 atm, g = 9.81 m/s2 .

Which of the following is the correct statement?   a. Irreversible engines have maximum efficiency   b. The increase in entropy is obtained from a given quantity of heat at a low temperature   c. The entropy represents a maximum amount of work obtainable per degree drop in temperature   d. All the reversible engines have the same efficiency   e. All the reversible and irreversible engines have the same efficiency   f. The change in entropy may be regarded as a measure of the rate of the availability of heat for transformation into work   g. All engines are designed as reversible to obtain maximum efficiency