Hot air balloon thermodynamics

In summary, the conversation discusses how hot air balloons maintain atmospheric pressure and constant volume, even when heated to increase their temperature. The speaker suggests that the decrease in density due to the increased temperature allows the balloon to remain at the same pressure. However, the other person questions whether the volume is truly constant, and explains that the decrease in density causes a buoyancy effect.
  • #1
gersetaffe
4
0
In hot air balloons the air inside the envelope stays at atmospheric pressure because of the hole in the bottom and the volume of the envelope is essentially constant. Yet in order to raise the balloon it must be heated which increases the its temperature. If the temperature increases how does the pressure and volume stay constant?

My guess is that the number of molecules of air in the balloon decreases (decreasing the density). The pressure stays the same because the increased temperature increases the kinetic energy of the remaining molecules.

What do you think? I'm not sure if my guess is correct.
 
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  • #2
What makes you think the volume is constant? When you heat the air the balloon gets bigger.
 
  • #3
Volume within the balloon is constant, but due to the higher temperature, the density is less inside the balloon than the surrounding cooler atmosphere, resulting in bouyancy effect.
 
  • #4
...so yes when you heat the air you reduce the number of molecules in the balloon.
 
  • #5


Your guess is partially correct. When the air inside the balloon is heated, the molecules gain kinetic energy and start moving faster, causing them to collide with each other and the walls of the balloon more frequently and with more force. This increase in molecular collisions creates an increase in pressure, causing the balloon to rise.

However, the volume of the balloon does not remain constant. As the air inside the balloon heats up, it expands and takes up more space. This increase in volume helps to maintain a constant pressure inside the balloon.

In summary, the increase in temperature causes an increase in pressure and volume, but the volume increase helps to maintain a constant pressure inside the balloon. This is because the increase in temperature also leads to an increase in the volume of the gas, which allows for more space for the molecules to move and collide, thus maintaining the pressure.
 

1. What is the principle behind hot air balloon flight?

The principle behind hot air balloon flight is based on the concept of buoyancy. Hot air is less dense than cold air, so when the air inside the balloon is heated, it becomes less dense and rises, carrying the balloon and its passengers with it.

2. How does temperature affect the performance of a hot air balloon?

The temperature of the air inside the balloon is crucial to its performance. The hotter the air, the more buoyant it becomes, and the higher the balloon can fly. On the other hand, colder air can cause the balloon to descend or even lose altitude.

3. What are the different components of a hot air balloon?

A hot air balloon is made up of three main components: the envelope (the fabric part of the balloon), the burner (which heats the air inside the envelope), and the basket (where the passengers and pilot stand). Additionally, there are also various ropes, cables, and vents that help control the balloon's flight.

4. How do hot air balloons maintain their altitude?

Hot air balloons maintain their altitude by controlling the temperature of the air inside the envelope. If the balloon starts to descend, the pilot can turn on the burner to heat the air and increase altitude. Similarly, if the balloon is flying too high, the pilot can open the vents to let out some hot air and decrease altitude.

5. What are the safety precautions for hot air balloon flights?

Some of the safety precautions for hot air balloon flights include proper weather assessment, regular maintenance of equipment, and following all regulations and guidelines set by the Federal Aviation Administration (FAA). Additionally, it is essential for pilots to have proper training and for passengers to listen to safety instructions before the flight.

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