Chapter 7, Problem 7.11E

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 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.

What does the exergy principle state? The exergy of an isolated system can never decreases, but always increases O The exergy of an isolated system can never increases, but always decreases O The exergy of an isolated system can either increases or decreases O None of the above

1. Water and air are used as working fluids in a counter-flow heat exchanger operating at steady state. Water enters as a saturated vapor at 300 kPa with a mass flow rate of 10 kg/s and exiting as saturated liquid. Air enters in a separate stream at 0°C, 100 kPa and exits at 37°C. Pressure changes and the heat transfer between the heat exchanger and its surroundings are negligible. Determine the rate of exergy destruction in the heat exchanger.

3.1 For discussion: (a) Is it possible for exergy to be negative? Discuss. (b) Consider an evacuated space with volume V as the system. Eval- uate its exergy and discuss. PH associated with (c) Is it possible for the specific physical exergy e' a stream of matter to be negative? Discuss.

When T > T0, the exergy and heat transfer are in the same direction.

Which of the following statements best describes the 2nd law of thermodynamics? The total entropy of a a reservoir must stay the same or increase. The change in internal energy for an ideal gas is given as A U=mc _▲T. V Heat energy will always be transferred from a hotter object to a colder object. Around a complete cycle, the net heat and net work additions must sum to zero. O A reversible cyclic engine can convert all the heat input it receives into useful work output.

1. A source of heat at 1000 K transfers 1000 kW of power to a power generation device, while producing 300 kW of useful work. Determine: a. The rate of exergy destruction in this process if the environment is at 300K. b. The second law efficiency of the system.

At a pressure of 1 bar, a temperature of 17 °C and a mass flow of 0.3 kg/s, air enters a stable insulated compressor and exits at 3 bar, 147 °C. Determine the power required by the compressor and the exergy destruction in kW. Express the exergy disappearance as a percentage according to the power required by the compressor. Changes in kinetic and potential energy will be neglected. dead state; T0=17 °C, P0=1 bar