Fundamentals of Heat Engines. Jamil Ghojel

is about 400 kJ h−1,What is the change in internal energy of the air 15 minutes after shutdown?If all the students and the lecture theatre are taken to be the system, how much does the system's internal energy change?How do you account for the increase in air temperature?

      6 1.15 The collecting panels of a small solar boiler receive radiation energy at the rate of 3400 kJ/m2 each hour during daylight. For a small rural power plant with 10 kW output, determine the required collector area if the electrical output is only 6% of the incident radiation.

      7 1.16 In a steady‐flow open system, a fluid flows at the rate of 4 kg/s. It enters the system at a pressure of 600 kPa, a velocity of 220 m/s, internal energy 2200 kJ/kg, and specific volume 0.42 m3/kg. It leaves the system at a pressure of 150 kPa, velocity of 145 m/s, internal energy 1650 kJ/kg, and specific volume 1.5 m3/kg. During its passage through the system, the substance has a loss by heat transfer of 40 kJ/kg to the surroundings. Determine the power of the system, stating whether it is from or to the system. Neglect any change of gravitational potential energy.

      8 1.17 Air enters a gas turbine system with a velocity of 105 m/s and has a specific volume of 0.8 m3/kg. The inlet area of the turbine is 0.05 m2. At exit, the air has a velocity of 135 m/s and specific volume of 1.5 m3/kg. In its passage through the turbine system, the specific enthalpy of the air is reduced by 145 kJ/kg and the air has a heat loss of 27 kJ/kg. DetermineThe mass flow rate of the air through the turbine systemThe exit area of the turbine system in m2The power developed by the turbine system in kilowatts

      9 1.18 A 1.0 m3 closed vessel is filled with air at pressure p = 7 bar and temperature T = 288 K. The vessel is heated until the air temperature reaches 373 K. DetermineThe mass of air in the vesselThe air pressure at the end of the heating processThe change of internal energy, enthalpy, and entropy of air as a result of heating

      10 1.19 A cylinder with a moving piston is filled with 2.5 kg of air. Initially, the pressure and temperature in the cylinder are, respectively, 0.8 MPa and 25 °C. If the air is heated to 100 °C at constant pressure, determineThe amount of heat inputWork doneChange of internal energy, enthalpy, and entropy of the airSpecific volume of the air at the start and end of the process.

      11 1.20 0.1 kg of air in the cylinder of a compression ignition (CI) engine undergoes polytropic compression during which the volume decrease 16 times and the pressure increases 45 times. If the initial temperature is 320 K, determineThe polytropic index of the compression processTemperature of the air at the end of compressionCompression workChange of internal energy, enthalpy ant entropyHeat added to the process

      12 1.21 1.0 kg of air undergoes a Carnot cycle in which the heat source is at 900 K and the heat sink at 300 K. if the minimum and maximum pressures in the cycle are 0.1 and 6.0 MPa, respectively, determineProperties at the characteristic pointsWork doneThermodynamic efficiency

      13 1.22 The following figure depicts a thermodynamic model for a reciprocating internal combustion engine with the control volume shown by the dashed line. The heat losses by heat transfer from the hot engine surfaces and the enthalpy of fuel can be assumed negligible.Write the general energy equation for the system.Determine the required rate of heat input if the engine is producing 120 kW of power, and the flow rate of inlet air and water flow rate in the cooling system are 0.15 kg/s and 4.4 kg/s, respectively. Take the exhaust (assumed air) temperature Texh = 507 °C, and the temperatures of the coolant Tc,in = 80 °C and Tc,out = 84 °C. The inlet air and the fuel are at 295 K.Determine the fuel consumption (in litres/h) if the lower heating value of the fuel is 43 500 kJ/kg and the fuel density is 850 kg/m3.