(2) Describe briefly why the following statements are wrong. (a) “Hot cup of coffee becoming cold spontaneously is an entropy-decreasing process. So the law of entropy increase can be violated." (b) “Air conditioners require bulky external unit, exhausting heat to outside. With the technology constantly advancing, external unit will be eliminated in the future."

(2) Describe briefly why the following statements are wrong. (a) “Hot cup of coffee becoming cold spontaneously is an entropy-decreasing process. So the law of entropy increase can be violated." (b) “Air conditioners require bulky external unit, exhausting heat to outside. With the technology constantly advancing, external unit will be eliminated in the future."

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

Fast ,Do not hold. Two heat engines receive heat from a source at temperature of 550◦C. Heat engine "A" receives 200 kJ of heat and rejects the waste heat to a sink at 180◦C. Heat engine "B" receives 180 kJ of heat and rejects the waste heat to a sink at 120◦C.(a) Caclualte the generated entropy, Sgen, in both processes.(b) Based on your answer in part (a), identify the heat transfer that is more irreversible.
Find the rate of entropy production and determine if the cycle operates irreversibly, reverisbly, or impossibly. The inventor claims that a power cycle operates between hot and cold reservoirs at 1200 K and 400 K, respectively, with Calculate the rate of entropy production for this cycle in kW / K. Enter the answer without units, but with a sign if applicable. This cycle operates irreversibly reversibly impossibly.
Air enters the turbine of a gas turbine at 1200 kPa, 1200 K, and expands to 100 kPa in two stages. Between the stages, the air is reheated at a constant pressure of 350 kPa to 1200 K. Both turbines have same isentropic efficiency 85% Determine, in kJ per kg of air flowing (a) the work developed by each stage. (b) the heat transfer for the reheat process. (c) the increase in net work as compared to a single stage of expansion with no reheat
Establish the increase of entropy principle.
An insulated, steady state piping system consists of flowing air that is combined from twopipes into a single outgoing pipe. Determine the temperature of the air at the exit, thediameter at the exit, and the rate of entropy production within the system. Assume: that air is an ideal gas (cp = 0.24 Btu/lb oR), that kinetic and potential energyeffects can be ignored, and the system is atmospheric pressure throughout.
- =2 A reversible power cycle R and an irreversible power cycle I te between the same two reservoirs. Each receives Qy from the hot reservoir. reversible cycle develops work Wy while the irreversible cycle develops work Wy. (a) Evaluate the rate of entropy generation o for cycle Iin terms of Wy, Wg and the rature Te of the cold reservoir. (b) Demonstrate that ¢ must be positive.
At the beginning of a cycle using air, the pressure, volume and temperature are 550 kN/m 2 , 0.025 m 3 and 15°C, respectively. The air is heatedat constant pressure until the temperature is 204°C. It is then expanded adiabatically until the temperature becomes 120°C. The air is cooled atconstant volume to a temperature of 15°C then restored to its original volume by isothermal compression. (a) Draw the pressure volume and temperature entropy diagram.(b) Determine for the cycle, the heat received,(c) the work done,(d) the thermal efficiency, Take Cp =1.00 kJ/kgK, Cp /Cv =1.4
An open feedwater heater is a direct-contact heat exchanger used in vapor power plants. Shown in the figure below are operating data for an open feedwater heater with H2O as the working fluid operating at steady state, where T1 = 41 °C. Ignoring stray heat transfer from the outside of the heat exchanger to its surroundings and kinetic and potential energy effects, determine the rate of entropy production, in kW/K.
Explain into details why thermodynamics depends on the entropy?
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.
0.05 kg of carbon dioxide (molecular weight 44), occupying a volume of 0.03 m3 at 1.025 bar, is compressed reversibly until the pressure is 6.15 bar. Calculate final temperature, the work done on the CO2, the heat flow to or from the cylinder walls, (i) When the process is according to law pv1.4 = constant, (ii) When the process is isothermal, (iii) When the process takes place in a perfectly thermally insulated cylinder. Assume CO2 to be a perfect gas, and take n = 1.3.
Steam enters a turbine at 70 bar, 500C, and leaves at 2 bar as a saturated vapor. Calculate the isentropic efficiency of the turbine. Assume adiabatic process and negligible changes in kinetic energy and potential energy.