[Thermodynamics I] Adding heat to a closed, rigid tank

In summary, the problem involves a closed, rigid tank containing 2kg of water initially at 80 degrees C and a quality of .6. Heat transfer occurs until the tank contains only saturated vapor at a higher pressure. The question asks to determine the amount of energy transfer by heat, in kJ, for the water as the system. To solve this, we can use the equations U = Q and pv = RT, along with the information about specific internal energy and specific volume from the steam tables. We can find the total enthalpy and volume at 80 degrees C, and then use the volume to find the identical volume in the superheated steam tables to calculate the energy transfer by heat.
  • #1
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Homework Statement


A closed, rigid tank contains 2kg of water initially at 80 degrees C and a quality of .6. Heat transfer occurs until the tank contains only saturated vapor at a higher pressure. Kinetic and potential energy effects are negligible. For the water as the system, determine the amount of energy transfer by heat, in kJ.


Homework Equations


U = Q - W, W = 0 => U = Q
mu = U
pv = RT

The Attempt at a Solution


I don't really know where to even begin. I know the volume is constant, and I assume that I need to find the specific internal energy for the water and water vapor at the initial and final temperatures. Given the initial temperature and knowing V is constant, I might be able to determine pressure? I can't figure out how I would find the temperature and pressure for the saturated water vapor state either.
 
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  • #2
hi, the question has given mass as 2kg, this helps in finding results from the sp. volume/sp.enthalpy from the steam tables..at 80C find hf & hg and similarly for sp.volume along with the quality, find the total enthalpy and volume at 80C, then, since, its a closed tank, the volume of matter remains the same but changes from liquid-vapour mixture to vapour condition. At, sat. vapour condition, only vapour remains but the volume remains the same which was found at 80C and with this volume, using steam tables look to match identical volumes in the superheated steam tables-might require interpolation..
 
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Related to [Thermodynamics I] Adding heat to a closed, rigid tank

1. Why is it important to add heat to a closed, rigid tank in thermodynamics?

In thermodynamics, the addition of heat to a closed, rigid tank is important because it allows for the transfer of energy into the system. This energy can then be used to do work or produce a change in the state of the system.

2. What happens to the temperature when heat is added to a closed, rigid tank?

When heat is added to a closed, rigid tank, the temperature of the system will increase. This is because the heat energy is transferred to the particles within the tank, causing them to vibrate and move faster, leading to an increase in temperature.

3. How does the addition of heat affect the pressure in a closed, rigid tank?

In a closed, rigid tank, the addition of heat will cause the pressure to increase. This is due to the fact that the increase in temperature leads to an increase in the average kinetic energy of the particles, causing them to collide more frequently and with more force, resulting in a higher pressure.

4. What is the relationship between heat, volume, and pressure in a closed, rigid tank?

In a closed, rigid tank, the relationship between heat, volume, and pressure is described by the ideal gas law, which states that as the temperature (which is affected by the addition of heat) and the number of particles remain constant, an increase in volume will result in a decrease in pressure and vice versa.

5. Can the addition of heat to a closed, rigid tank result in a change of phase?

Yes, the addition of heat to a closed, rigid tank can result in a change of phase. This is because as the temperature increases, the molecules within the tank will gain enough energy to overcome the intermolecular forces holding them together, leading to a change from a liquid to a gas phase, for example.

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