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1

You might want to define what you mean by "efficient" better - but assuming you want to accelerate the air flow, then the most important parameter is the ratio of input to output diameter. Next, you want to minimize the length of the nozzle (since a longer nozzle implies more drag) and in particular the length of the nozzle where your cross section is narrow ...


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Wind is a solar powered flow of the atmosphere. The atmosphere is not uniformly heated: different areas have different solar power input. This uneven heating arises because some areas are in daylight, whereas others are in night, and different regions have different amounts of cloud cover and different colored terrain, so the albedo is uneven. Uneven ...


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From the Outside Your intuition is right. Rayleigh Scattering would come into effect, making the insides red and the outsides more blue. If the sun is at your back, or if the angle of sun-air-you is a right angle, you will still see light coming off of the air. However, this reflected light may be faint enough in places that you get the color of the night ...


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There's no uniform density of heated air. It depends on the temperature (higher T -> lower density) but also on the ambient air pressure. In Denver, cold air is less dense, because the ambient pressure is lower. But this same effect also increases the density of hot air, by the same percentage. So, the result is that the lift of a balloon decreases with ...


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So I found the answer....I was not taking the final step of multiplying The difference in density between the surrounding air and the heated air and then multiplying by the envelope volume. I was just focusing on the difference and getting stuck there. I chose Denver because it's a mile above sea level with a known air density. I could have chosen Mt Everest ...


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Given the imprecision in these numbers, that means that you can lift anywhere between 0 and 0.1 kg per m^3 of air. Per Wikipedia, a typical hot air balloon holds 2,800 m^3 of air in the envelope, so it can suspend something between 0 and 280 kg in the basket. A typical human weighs under 100kg, so you could probably lift between one and three people with a ...


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Your breath is the same temperature either way. The difference is how much ambient air is brought along with the breath by the time it reaches the object. Emitting a thin and fast stream of air will cause a lot of other air to follow along with it. When you are blowing on the soup to cool it, what you're really doing is using your breath to move a lot of ...


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In general, the idea looks like this: you keep track of a "stuff" (in this case both air and energy) as it flows into and out-of some "perfectly mixed reactors" (in this case "reactor" means a tank where things which react are often stored). The "stuff" can be anything which obeys a conservation law in that context, so momentum and energy and volume (at ...


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If you have a volume of air $V$ at temperature $T_B$, then you replace a part of that air with air of volume $\Delta V$ and temperature $T_A$, then the new average temperature is a weighted average of the temperatures of the room's air and the new air. $$T_B(t+\Delta t) = \frac{(V-\Delta V) T_B(t) + \Delta V T_A(t)}{V}$$ We get a symmetrical expression for ...



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