Question

1. In an industrial process, a tank containing 200 liters of
water at 372 K at a constant pressure is used as a thermal energy
storage device. The device is used to heat a residential space that
is maintained 293 K. There is a negligible change in the volume of
the water. The water is stirred during this process to maintain a
uniformly distributed temperature. During the process, the
convective heat transfer coefficient between the water and the
space is 12.0 W/(m^{2}K) and the surface area equals 5.0
m^{2}. The residential space remains at a constant
temperature of 293 K and the thermal storage unit can be used until
its temperature reaches 300 K. Neglect the work associated with
stirring the tank and thermal radiation heat transfer.

a) How long will the thermal energy storage unit provide energy to the system?

b) Calculate the total heat flow in Joules that were added to the residential space from

the thermal energy storage device.

Answer #1

(d) In a closed industrial process 2 .5 kg of water at an
initial temperature of 15°C is continually stirred whilst being
heated. If the net heat transferred to the system is 3 kJ and the
final temperature of the water is 75°C, determine:
i.The internal energy change of the water
ii.The work transferred (stating the direction-in or out)of the
mechanical stirrer.
iii.The additional heat flow required for the same temperature
increase if there were no work transfer.
For parts...

A closed, rigid steel tank contains 1 lbm of water, initially at
260 F and a quality of 60%. The tank is fitted with a paddle wheel
and the water is stirred until the temperature is 350 F. The tank
is well insulated on the outside and the steel is in thermal
equilibrium with the water. The mass of the steel tank itself (not
including water) is 60 lbm and the specific heat of the tank is
0.115 Btu/lbm·R. Changes...

A closed, rigid steel tank contains 1 lbm of water, initially at
260F and a quality of 60%. The tank is fitted with a paddle wheel
and the water is stirred until the temperature is 350F. The tank
is well insulated on the outside and the steel is in thermal
equilibrium with the water. The mass of the steel tank itself (not
including water) is 60 lbm and the specific heat of the tank is
0.115 Btu/lbm·R. Changes in kinetic...

A rigid copper tank, initially containing 1 m3 of air at 295 K,
4 bar, is connected by a valve to a large supply line carrying air
at 295 K, 15 bar. The valve is opened only as long as required to
fill the tank with air to a pressure of 15 bar. Finally, the air in
the tank is at 310 K. The copper tank, which has a mass of 20 kg,
is at the same temperature as the...

150 grams of boiling water (temperature 100°C, heat capacity 4.2
J/gram/K) are poured into an aluminum pan whose mass is 970 grams
and initial temperature 25°C (the heat capacity of aluminum is 0.9
J/gram/K). (a) After a short time, what is the temperature of the
water?
(b) What simplifying assumptions did you have to make?
The thermal energy of the aluminum doesn't change.
Energy transfer between the system (water plus pan) and the
surroundings was negligible during this time.
The...

A piston-cylinder assembly containing 3 kg of an ideal gas
undergoes a constant pressure process from an initial volume of 48
m3 to a final volume of 30 m3 . During the
process, the piston supplies 1.2 MJ of work to the gas. The gas has
a constant specific heat at constant volume of 1.80 kJ/(kg∙K) and a
specific gas constant of 1.48 kJ/(kg∙K). Neglect potential and
kinetic energy changes.
a. Determine the initial specific volume of the gas in...

0.100 kg of water at 10∘C is added to 0.300 kg of soup at 50∘C.
Assume complete transfer of thermal energy from soup to the water,
with no transfer of energy to the environment. Specific heat of
water is 4180 J/kg⋅∘C. The soup has the same specific heat as
water.
A) Determine the final temperature? Express in Celsius
B) Estimate the entropy change of this water-soup system during
the process using the actual temperatures to determine the heat
transferred and...

A mass of one kg of water within a piston–cylinder assembly
undergoes a constant-pressure process from saturated vapor at 500
kPa to a temperature of 260°C. Kinetic and potential energy effects
are negligible. For the water:
a) Evaluate the work, in kJ,
b) If the work is 30 kJ, evaluate the heat transfer, in kJ,
c) If the heat transfer is negligible, evaluate the entropy
production in kJ/K
d) Determine if the process is reversible, irreversible, or
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A house with 200-m2 floor space is heated with geothermal water
flowing through pipes laid in the ground under the floor. The walls
of the house are 4 m high, and there are 8 single-paned windows in
the house that are 1.2 m wide and 1.8 m high. The house has R-4
insulation (where R= 1/U is the overall unit thermal resistance(the
R-value) and U is the overall heat transfer coefficient) in the
walls and R-5 on the ceiling. The...

Calculate the entropy production for the
piston-cylinder power producing cycle you analyzed in,
problem 1.
Problem 1: A piston cylinder device has a
volume of 0.04 m3 and initially contains air at 293 K
and 1 bar. This device is used to perform a cycle in which the gas
is heated at a constant volume until the temperature reaches 1000
K. The air is allowed to expand following an isothermal process
until the volume is 3.5 times the original volume....

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