Architectural Designs

do spheres really experience less heat loss than other shapes?

i am about to do an experiment on shapes and how their surface area relates to the amount of heat loss. I am wondering if a sphere is the ideal shape because of it has minimal surface area while having the greatest volume. The goal of my assignment is to design and build a prototype (can be a model) of an aspect for water heating in a solar home(meaning it has to be energy efficient). This design has to be innovative which is why i chose a sphere (since it SHOULD reduce heat loss compared to commercial cylinders). Any feedback would be great thanks!

Public Comments

1. I would agree that minimum surface area for a given volume has to give the minimum heat loss if maximum heat loss occurs through the surface. Sounds to be quite innovative. Good luck.
2. Heat loss reduction is a good idea, shape is important but it can be overcome with wrapping lots of insulation as well. How about some other innovations? How about using a water resevior to carry away heat from the refrigerator coils and other waste heat producing devices: - air conditioner coils - outlet for a clothes dryer -the waste water that was heated in dishwasher and clotheswasher - the heat still in your shower/bathwater when you let it run down the drain All these heat sources could be routed and captured by a simple water heat exchange system, letting it do its work again. This is common in industrial settings where the $ can rackup, but I'm sure on a smaller scale it would work great. To make this work you would not have very hot water in the main tank, just warm, it needs to be cooler than the waste heat streams. This warm water would then be piped through a tankless hot water heater for on-demand hot water. The advantage would be pre-heated water, thus requiring alot less energy to heat the rest of the way up. You also minimize losses in energy by storing the water at lower temps, thus reducing the driving force for heat loss I would think that with the solar heat really working and some recaptured heat the tankless system would hardly work at all. Only when it was night would it even kick on
3. Yes a sphere should have less heat loss due to less surface area. However it is harder and therefore more costly to make than a cylinder and in the same diameter space you can fit a larger volume cylinder. I would bet that the type and quantity of insulating material is more important that the general shape within reason.
4. most of the answers are covering it well..... Nice Hint : avoid sharp shapes & any shape with edges , because any edge a flux gets concentrated at it , if that was shear flux , thermal , stresses or whatever....... and as u c among them sphere is the best
5. Yes, a sphere is the best shape. But you may run into problems when it comes to the "real world". There has to a compromise when true science and reality meet. I understand what you are trying to do, but who would buy a sphere hot water tank? Go look at your own hot water tank and figure how big it would be if it was a sphere holding the same amount of water. I wonder if would be a good idea to have two or more smaller spheres stacked on top of each other instead of one big tank.
6. The volume of a sphere of radius r i s (4/3)pi r^3 and its surface area is 4pi r^2. The volume over area ratio is r/3. The volume of a cube of 2r sides is (2r)^3 and its surface area is 6(2r)^2. The Volume over area ratio is still r/3. The above shows that there is no advantage using a spherical container over that of a cubical container in terms of heat loss. A spherical container would be more difficult to fabricate, however the thickness of the material needed to make one is less than that of a cubical container. But that is another matter.