Soal soal dibawah ini merupakan merupakan contoh penerapan dari konsep yang teah dijelaskan dalam pertemuan ke 9 dan 10, baik substansi materi yang tertuang dalam e learning termo maupun saat perkuliahan tatap muka di ruang kelas

EXAMPLE E5-1 An electric heater is used to raise the temperature of 1000 L of water stored in a tank from 15oC to70oC . Due to poor insulation, 18 MJ of heat is lost to theatmosphere at 15oC . Using the SL (solid/liquid) model for water, determine (a) the electrical work consumption in kW . h, (b) the energetic efficiency, and (c) the entropy generationin the heater's universe. [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) -68.73 kW.h, (b) 92.7%, (c) 791 kJ/K Anim. E5-1 (click)

EXAMPLE E5-2 An aluminum block of mass 2000 kg cools

down from an initial temperature of 200oC to the atmospheric

temperature of 25oC. Determine the (a) heat transfer, (b) entropy generated in the system's universe. (c) What-if- Scenario: How would the answer in part (a) change if the

initial temperature were 800oC? Neglect KE and PE. [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) -315 MJ, (b) 225.24 kJ/K, (c) -135 MJ Anim. E5-2 (click)

EXAMPLE E5-3 A 5 L piston-cylinder device contains steam at a pressure of 200 kPa and a quality of 20%. Heat is transferred from a TER at 1000 K until the volume doubles (see Anim. 5.A.pConstHeating). No heat transfer occurs

between steam and the atmosphere, which is at 25oC and100 kPa. Determine (a) the heat transfer, (b) work transfer, (c) the entropy generation in the system's universe. [ M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 12.44 kJ, (b) 1kJ, (c) 0.0192 kJ/K Anim. E5-3 (click)

EXAMPLE E5-4 A piston cylinder device, shown in Fig. 5.18,

contains 0.2 m3 of R-134a at -20oC and a quality of 20%. The spring is linear and has a spring constant of 100 kN/m. The

refrigerant is heated until its temperature reaches 25oC. Ifthe cross-sectional area of the piston is 0.2 m2, determine (a)the mass of the refrigerant, (b) the pressure when the piston

reaches the stops at a volume of 0.4 m3, (c) the final pressure, and (d) the work and heat transfer during theentire process. (d) the work and heat transfer during the entire process. What-if-Scenario: (e) What would be the

heat transfer if the final temperature were 50oC? [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 6.7 kg, (b)233.7 kPa, (c)374.4 kPa (d)36.74 kJ,1271.2 kJ, (e)1406 kJ Anim. E5-4 (click)

EXAMPLE E5-5 A 2 m3 insulated rigid tank contains hydrogen

at the atmospheric conditions of 100 kPa and 200C. A paddle wheel transfers 100 kJ of shaft work into the systemand the system reaches equilibrium after a few minutes. Determine (a) the final temperature of the gas, and (b) entropy generated in the system during the process. (c) What-if- Scenario: What would be the entropy generation in the system's universe if the tank were not insulated? [ M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: a) 352.5 K, (b) 0.31 kJ/K, (c) 0.34 kJ/K Anim. E5-5 (click)

EXAMPLE E5-6 An insulated piston-cylinder device contains0.01 kg of steam at a pressure of 500 kPa, 400oC . The steam expands in an internally reversible manner until it is saturated. Determine (a) the pressure, and (b) temperature of the steam at the end of the expansion process. Also determine (c) the boundary work transfer. [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 27.92 kPa (b) 67.46oC (c) 4.92 kJ Anim. E5-6 (click)

EXAMPLE E5-7 A rigid tank with a volume of 0.1 m3 contains

steam of quality 2% at a temperature of 25oC. A resistance heater within the tank is turned on, which operates for 30 minutes drawing a current of 2 A from a 120-V source. At the same time 50 kJ of heat is lost from the tank to the

atmosphere at 25oC. Determine the (a) final pressure, (b) final temperature. (c) What-if-Scenario: How would the answers change if the initial quality were 1%? [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 515.2 kPa, (b) 700.92oC, (c) 259.3 kPa, 128oC. Anim. E5-7 (click)

EXAMPLE E5-8 An insulated electrically heated teapot with a power consumption rate of 1 kW contains 1 L of water at25oC. (a) Determine the time it takes for the water to reachthe boiling point after the heater is turned on. (b) How much longer should the heating be continued in order to completely boil off the water? Assume the atmospheric pressure to be100 kPa. (c) What-if-Scenario: How would the answers change if the water were heated on top of a mountain where the atmospheric pressure is 90 kPa? [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 312 s, (b) 2258s, (c) 300 s, 2258 s Anim. E5-8 (click)

EXAMPLE E5-9 A handheld bicycle pump contains 50 cc of air

at 25oC and 100 kPa. The exit hole is blocked and the piston is pressed until the pressure increases to 300 kPa. Determine the work and heat transfer during the process if it is carried out (a) very quickly, (b) very slowly, (c) at an intermediate speed where a polytropic coefficient of n = 1.3 is applicable. Assume perfect gas behavior for air. [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) -0.0046 kJ,-0.0046 kJ, (b) -0.0055 kJ, -0.0055kJ, (c) -0.0048 kJ,-0.0012 kJ

EXAMPLE E5-10 A tank contains 1000 kg of propane at 8 MPa

and 25oC. If the atmospheric pressure is 100 kPa, determine (a) The mass of propane that would flash into vapor if thewall ruptures. (b) Calculate the explosive energy in the tank in TNT equivalence by assuming the expansion process to beisentropic. [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 337 kg, (c) 7.57 kg TNT Figure E5-10

EXAMPLE E5-11 A 40 kg aluminum block at 100oC is dropped into an insulated tank that contains an unknown mass of

liquid water at 20oC. After the thermal equilibrium is

established the temperature is measured as 22oC. Determine (a) the mass of water, (b) the entropy generated in the system's universe. (c) What-if-Scenario: How would the answer in part (b) change if the temperature of the blockwere 200oC? [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 335.6 kg, (b) 1.1 kJ/K, (c) 4.104 kJ/K Anim. E5-11 (click)

EXAMPLE E5-12 Two 1 m3 rigid tanks, A and B, contain R-134a at a pressure of 300 kPa and 100 kPa respectively, and are connected by a valve. The tanks are in thermal

equilibrium with the atmosphere which is at 25oC. The valve is now opened and after a sufficient time, a uniform state at25oC is formed. Determine (a) the final pressure, (b) heattransfer, (c) entropy generated, and (d) What-if-Scenario: How would the entropy generation change if the pressure of the tank A is 500 kPa in the beginning? [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 202.3 kPa, (b) 11.6 kJ, (c) 0.18 kJ/K, (d) 0.53 kJ/K Anim. E5-12 (click)

EXAMPLE E5-13 A well insulated rigid tank is partitioned into two chambers (see Anim. 5.C.suddenExpansion), with

volumes 0.1 m3 and 0.8 m3 respectively. The smaller chamber contains steam at 100 kPa and 50% quality while the larger chamber is completely evacuated. The stop is removed and steam is allowed to expand to the entire

volume of the tank. Determine the (a) change in temperature, (b) entropy generated in the process. (c) What-if-Scenario: What would be the temperature changeif steam could be treated as an ideal gas? [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) -52.14oC, (b) 0.0626 kJ/K Anim. E5-13 (click)

EXAMPLE E5-14 A 1 m3 evacuated, insulated rigid tank is being filled from a supply line carrying steam at 100 kPa and400oC (see Anim. 5.E.charging). determine (a) the finaltemperature, (b) entropy generated during the process. Assume the atmospheric temperature to be 25oC and thefinal pressure in the tank to be 100kPa. Use the PG model forsteam. [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 894 K, (b) 0.129 kJ/kg K Anim. E5-14 (click)

EXAMPLE E5-15 A pressure cooker has a volume of 5 L and

an operating temperature of 120oC. Initially, one-half of the volume is filled with liquid water and the rest with vapor. Heat is supplied at a rate of 1 kW. Determine (a) the operating pressure, (b) mass of the pressure regulator that

can be supported by a flow area of 10 mm2, and (c) time required for all the liquid to completely vaporize. (d) What- if-Scenario: How would the answer in part (c) change if the operating pressure were same as the ambient pressure of100 kPa? [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 198.5 kPa, (b) 0.1 kg, (c) 1.44 h, (d) 1.50 h Figure E5-15

EXAMPLE E5-16 Heat is added to 1 m3 rigid tank containing steam at a rate of 1kW. Determine the rate of increase of (a) temperature, and (b) pressure at an instant when the

pressure and temperature inside are 10 kPa and 200oC respectively. Use the PG model for steam. [M a n u a l S o l u t i on] [ T EST S o l u t i on]

Answers: (a) 15.5 K/s, (b) 0.327 kPa/s, (c) 0.327 kPa/s Figure E5-16

EXAMPLE E5-17 A sub-compact car with a mass of 1000 kg accelerates from rest to 100 km/h in 30 s on a road with an

upward slope of 10o. Determine (a) the additional powerrequirement due to climbing and acceleration. [M a n u a l S o l u t i on]

Answers: (a) 36.5 kW

EXAMPLE E5-18 A 1 m3 insulated rigid tank is being filled

from a supply line carrying steam at 100 kPa and 400oC. Determine the (a) rate of change of temperature, and (b) pressure at an instant when the pressure and temperature

inside the tank are 50 kPa and 400oC respectively, and the mass flow rate into the tank is 0.01 kg/s. Assume the steam to behave as a perfect gas. (c) What-if-Scenario: How would the answers change if the phase-change model wereused? [M a n u a l So l u t i on] [ T EST S o l u t i on]

Answers: (a) 13.7 K/s, (b) 4.12 kPa/s Figure E5-18