Chapter 7, Problem 7.145EP

Vapor Nozzle Due to a failure, ammonia in a large container overheats to 14 bar, 300°C. At this state, a small crack opens in the container that acts as a nozzle. The outside environment is at 1bar, 25°C, and the mass flow rate of ammonia is 10 kg/s. Assume negligible nozzle inlet velocity and adiabatic reversible flow. Determine the exit velocity, and the exit cross section.

Given 0.603MW electrical power supplied to a boiler when the temperature of the entering water is 20 C and the exiting temperature is 89 C. The flow of.the pressured water is 2 Kg/s. There is a negligible pressure drop through this boiler and it operates at a constant pressure of 3 bars. The specific heat is c = 4,370 J/(Kg K).  a) Calculate the total rate of entropy production b) Calculate the total rate of exergy destruction (W). The dead state temperature is 293.2 K and pressure is 1 bar. c) Calculate the mass flowrate of fuel (natural gas, CH4) required to heat the water flow to the conditions of the problem if the electrical heating device is replaced with a gas fired boiler. The high heating value (HHV) of the fuel is 50.02 MJ/kg.

2.A piston cylinder arrangement contains steam at 10MPaa saturated liquid. Heat was transferred isothermally so that the pressure reaches 2MPaa. а. Find the final temperature of the steam. b. Find the change of entropy in kJ/kg if there is no entropy production.

A turbine, operating under steady- flow conditions, reccives 1000 kg/min of stcam. At the inlet, the pressure is 30 bar, the temperature is 400°C, the velocity At the exit, the pressure is 0.7 bar, the quality is (100%), and the velocity is 100 m/s. If the turbine produced a power output of 9300 KW. By using the energy balance of open system with sutable tables, answer the following: (a) What are the main assumptions ? (b) Calculate dh, AKe ? (c) Calculate the rate of heat transfer between the turbine and surroundings, in kW.

Air as ideal gas in the closed system, find the change of entropy from the initial to the final state, in Btu/lb oR ( degree R ). T1 = 360 oF (degree F), P1 = 14.7 psia T2 = 540 oF (degree F), P2 = 58.8 psia

heat engine used a steam as working fluid has 3 kg/s and initial the steam undergoes to expansion process is 8 bar, dryness fraction ( 65) percent , and the expansion follows the law (PV¹.¹-C), down to a pressure of 0.3 bar. Calculate the change of entropy of steam during the process.

Air enters an insulated compressor at ambient conditions, 100 kPa, 20 oC at the rate of 0.2 kg/s and exits at 500 K. The isentropic efficiency of the compressor is 70%. What is the exit pressure? How much power is required to drive the compressor? Assume specific heats at room temperatures.

1. A piston/cylinder setup contains air at 100 kPa,400 K that is compressed to a final pressure of 1000 kPa. Consider two different processes: (a) a reversible adiabatic process and (b) a reversible isothermal process.

Q3. 1000 kJ of heat are transferred irreversibly and isothermally at atemperature of 800 K. The temperature of surrounding is 300 K. a. What is the maximum work that can be obtained frome this isothermal heat transfer? b. What is the amount of heat that regected to the surrounding? c. What is the entropy change of the two reservoirs? d. What is the total entropy change? Ans: a. 625 kJ b. 375 kJ c.-1.2, 1.25KJ/k d. zero