Heating Water with vapor at certain pressure

In summary, the problem involves using vapor at 180 °C and 1.5 bar of pressure to heat water from 10 °C to 50 °C. The approach is to use an energy balance, specifically an enthalpy balance, to determine the amount of cold water needed to mix with the vapor. The equation Q = mc (Tf-Ti) is considered, but the challenge is to obtain the value of Q. Suggestions for solving this problem are welcomed.
  • #1
DelfinDelfin
2
1

Homework Statement



We wish to heat water from 10 °C to 50 °C using vapor at 180 °C and 1.5 bar of pressure. How much cold water do we need to mix with every Kg of vapor to obtain the result?

Homework Equations


I am not sure. I think the problem is related with exergy and energy balance

The Attempt at a Solution


This is the first time I see a problem that relates liquid with gases this way. I only thought about Q = mc (Tf-Ti). So if we knew the energy stored in 1 kg of vapor at 180 C and 1.5 bar, we could assume that the energy is going to be transferred in form of heat to the water, we will have m = Q/(4.186*40 °C). But I don't see how to obtain Q. Or maybe I need a different approach. I will appreciate any suggestions. Thanks
 
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  • #2
Hello DD, :welcome:

What you want is an energy balance (exergy is not conserved!) - in this case an enthalpy balance.
Write down the situation before mixing on the left and after mixing on the right of an equals sign and solve for the amount of water.
 

1. How does heating water with vapor at certain pressure work?

When water is heated with vapor at a certain pressure, the vapor transfers its heat energy to the water molecules, causing them to move faster and increase in temperature. This process is known as convection, where the warmer vapor rises and the cooler water sinks, creating a cycle of heat transfer.

2. What is the significance of using a specific pressure when heating water with vapor?

The pressure at which the water is heated with vapor affects the boiling point of the water. The higher the pressure, the higher the boiling point of water, which means it will take longer for the water to reach its boiling point and convert into vapor. This is important for various industrial and scientific processes that require precise temperature control.

3. Can heating water with vapor at certain pressure cause any changes in the water's properties?

Yes, heating water with vapor at a specific pressure can lead to changes in the water's physical and chemical properties. For example, the increased temperature can cause the water molecules to break apart and form steam, which is a gas. It can also change the solubility and pH of the water.

4. Is heating water with vapor at certain pressure a safe method?

When done correctly and with the proper equipment, heating water with vapor at a specific pressure is a safe method. However, it is crucial to follow safety protocols and use caution, as the high temperature and pressure involved can be dangerous if mishandled.

5. What are some practical applications of heating water with vapor at a specific pressure?

There are various practical applications of heating water with vapor at a specific pressure, such as in power plants to generate electricity, in steam engines for transportation, in industrial processes for heating and cleaning, and in scientific experiments that require precise temperature control. It is also commonly used in home appliances like electric kettles and pressure cookers.

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