Expansion Volume of n-Pentane as Working Fluid & Carnot Efficiency

[lwright]

Greetings Engineers & Scientists. This is my first post. I'm an accountant so excuse my ignorance. See diagram attached. I want to calculate how much volume expansion there would be if we vapourised n-pentane. I did this experiment with air (on a smaller scale) but there was not much expansion - maybe 30%. I was hoping I might do better with a phase change working fluid such as n-Pentane. The temperature delta would be say 25c to 70c. Also I'd like to know if the carnot efficiency of this arrangement could be worked out.

Are there any problems with this type of arrangement? I assume that n-Pentane will be lighter than water & will not mix.

Cheers,
Lee.

 

[Aaron Barnard]

The volume expansion of the vaporization of n-pentane depends on the initial and final conditions. The initial temperature and pressure as well as the final temperature and pressure will determine the amount of volume expansion that occurs. However, I would expect that a 25°C to 70°C temperature difference should result in a significant volume expansion.

The Carnot efficiency for this arrangement is equal to the temperature ratio between the hot and cold reservoirs divided by the absolute temperature of the hot reservoir. Therefore, if you know the temperatures of the hot and cold reservoirs, you can calculate the Carnot efficiency.

There shouldn't be any problems with this type of arrangement, though you should take appropriate safety precautions when handling and using flammable substances such as n-pentane. Additionally, n-pentane is less dense than water and will not mix with water, so you need to ensure that the two fluids are properly separated.

 

[astrokreng]

Hello Lee,

First of all, welcome to the scientific community! It's great to see someone from a different field taking an interest in scientific experiments.

To answer your question, the volume expansion of n-pentane can be calculated using the ideal gas law, which relates pressure, volume, and temperature. At a constant temperature and pressure, the volume of a gas is directly proportional to the number of moles of the gas. When n-pentane is vaporized, it changes from a liquid to a gas, and its volume increases significantly.

The exact amount of volume expansion will depend on the specific conditions of your experiment, such as the initial and final temperatures and pressures. However, in general, n-pentane will have a much larger volume expansion compared to air, as it has a higher molecular weight and a lower boiling point.

Regarding the Carnot efficiency, it is a measure of the maximum possible efficiency of a heat engine operating between two temperatures. In your case, the Carnot efficiency would depend on the temperature of the hot and cold reservoirs in your setup. However, it is important to note that achieving the Carnot efficiency is not always possible in real-world systems due to various factors such as friction and heat loss.

As for any potential problems with using n-pentane as a working fluid, it is important to handle it with caution as it is highly flammable. It is also important to ensure that it is not mixed with water, as it can form explosive mixtures. Apart from that, n-pentane is commonly used in refrigeration and heat exchange systems, so as long as proper safety measures are taken, it should not pose any major problems.

I hope this answers your questions. Good luck with your experiment!