A rigid, well-insulated tank contains a two-phase mixture consisting of .005 ft^3 saturated liquid water and OSK1.2 ft^3 of saturated water vapor, ini

Marvin Mccormick

Marvin Mccormick

Answered question

2021-02-22

A rigid, well-insulated tank contains a two-phase mixture consisting of .005ft3 saturated liquid water and 1.2ft3 of saturated water vapor, initially at 14.7lbfin2.A paddlewheel stirs the mixture until only saturated vapor remains in the tank. Kinetic and potential energy effects are negligible. For the water, determine the amount of energy transfer by work, in Btu.

Answer & Explanation

Theodore Schwartz

Theodore Schwartz

Skilled2021-02-23Added 99 answers

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Eliza Beth13

Eliza Beth13

Skilled2023-06-19Added 130 answers

The energy transfer by work can be calculated as:
ΔU=QW
where:
ΔU represents the change in internal energy,
Q represents the heat added to the system,
W represents the work done by the system.
Since the paddlewheel stirs the mixture until only saturated vapor remains in the tank, we can assume that the process occurs at constant volume (isochoric process).
For an isochoric process, the work done is given by:
W=PΔV
where:
P represents the pressure,
ΔV represents the change in volume.
In this case, the volume changes from the initial volume to zero, as only saturated vapor remains in the tank. Therefore, ΔV=Vi, where Vi represents the initial volume of the mixture.
The work done can be expressed as:
W=PVi
Now, we need to determine the pressure P in order to calculate the work done. The initial pressure of the system is given as 14.7 lbfin2, which needs to be converted to the appropriate unit system.
Since we want the answer in British thermal units (Btu), we need to convert the pressure from lbfin2 to Btu.
The conversion factor is:
1 Btu = 778 ft lbfft
To convert lbfin2 to ft lbfft, we can use the conversion factor:
1 ft = 12 inches
Therefore, the conversion can be done as follows:
Pconverted=Pinitial×(112)2×778
Substituting the values, we get:
Pconverted=14.7×(112)2×778
Finally, we can calculate the work done:
W=Pconverted×Vi
Substituting the given initial volumes, we have:
W=Pconverted×(0.05+1.2)
Simplifying this expression will give us the amount of energy transfer by work, in Btu.
madeleinejames20

madeleinejames20

Skilled2023-06-19Added 165 answers

Step 1: Let's start by finding the initial state and the final state of the mixture.
Given:
Initial volume of saturated liquid water (Vliq) = 0.05 ft3
Initial volume of saturated water vapor (Vvap) = 1.2 ft3
Initial pressure (Pinitial) = 14.7 lbfin2
We know that the total volume of the mixture is the sum of the volumes of the liquid water and the water vapor:
Vtotal, initial=Vliq+Vvap
Substituting the given values:
Vtotal, initial=0.05+1.2=1.25 ft3
Since the tank is rigid, the volume remains constant throughout the process. Therefore, the final volume (Vtotal, final) is also 1.25 ft3.
To find the final pressure (Pfinal), we use the fact that only saturated vapor remains in the tank. At saturated conditions, the pressure and temperature are related by the saturation pressure-temperature relationship.
Step 2: Now, we can determine the initial temperature (Tinitial) corresponding to the initial pressure (Pinitial) using the saturation temperature-pressure table or steam tables. Let's assume the initial temperature is Tinitial.
After stirring, only saturated vapor remains in the tank, so the final temperature (Tfinal) is equal to the saturation temperature at the final pressure (Pfinal). Let's assume the final temperature is Tfinal.
Now, we need to calculate the energy transfer by work. For an ideal gas process, the work done can be calculated using the equation:
W=P·ΔV
Since the volume remains constant, the change in volume (ΔV) is zero, and therefore the work done is zero.
Hence, the amount of energy transfer by work, in Btu, is 0 Btu.
Therefore, W=0 Btu.

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