Chapter 7, Problem 7.133EP

2000 kg cast iron hoisin at 350 degree Celsius is quenched in 4000 kg of water at 15 degree Celsius. Find the amount of heat transferred to the water bath, entropy change for water and cast iron, use the entropy generation to prove that the entire system does not violate the second law of thermodynamics. Water specific heat of 4.18kj/kg.k, cast iron specific heat of 0.42kj/kg.k

Water in a tank can be heated from T; to T, if by: case (1) Adding heat from external source or case (2) Using electric heater. i The entropy generation will be: Select one: A. Zero in both cases. B. Always Greater in case (1). C. Always Greater in case (2). D. Greater or Lower in any case depending on other operating parameters. E. The same "Non-zero" value in both cases.

same compressor inlet and exit conditions. Answers: (a) 4.33, ing the waste heat to the outdoor air at 34°C. The - pressor at 400 kPa as a saturated vapor at a rate of 80 L/min COP, (b) the maximum COP, and (c) the minimum volume and leaves at 1200 kPa and 70°C. Determine (a) the actual working fluid is used to keep a room at 23°C by reject- An air-conditioner with refrigerant-134a as the and lights amounts to 900 W. The refrigerant enters the com- 250 kJ/min while the heat generated by the computer, TV, gains heat through the walls and the windows at a rate of 6-108 room flow rate of the refrigerant at the compressor inlet for (b) 26.9, (c) 12.9 L/min G.000 Он 1.2 MPa 70°C Condenser Expansion valve Compressor 400 kPa Evaporator sat. vapor

Round eveything to 4 decimal places. Saturated steam at 150°C is used as a working fluid for a device that supplies heat to a reservoir with a temperature of 250°C. Since the device is not 100% efficient, waste heat is produced to a sink of cooling water at 10°C. To be able to maintain the temperature in the reservoir, 2500 kJ of heat should be supplied, is this possible? Prove using entropy. Assume that the working fluid leaves as liquid water at 15°C.

A flashed-steam geothermal power plant is located where underground hot water is available as compressed liquid at 2610 kPa and 250 C. The flashed steam enters a turbine at 557 kPa, 98% quality and expands to 10 kPa. The flow rate from the well is 40 kg/s. Mechanical efficiency is 90% and generator efficiency is 92%. Determine the power produced by the plant in KW.

Q1: A 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 0.15 , and the expansion follows the law (PV1.=C)down to a pressure of O.3 bar. Calculate the change of entropy of steam during the process.

How did Sadi Carnot theorize to improve the 3% efficiency of early steam engine during his time?

Isentropic efficiency of a turbine. If the process between the inlet state and the exit pressure.

In a Bell-Coleman cycle air is drawn into the cylinder of a compressor at a pressure of 1 bar and 5°C. It is then compressed adiabatically to 5 bar (in the reversible manner) at which pressure it is cooled to 15°C, it is then expanded in the expansion cylinder to atmospheric pressure and discharged into the refrigerated chamber. Law kg тin are. of expansion is PV1.2-C. The COP of the refrigerating plant and capacity of the plant in TR for a mass flow rate of 10