tag:blogger.com,1999:blog-5657893141930894288.post4788175934763423714..comments2024-01-23T12:33:18.729-08:00Comments on the mudcat mundane: Party Tricks and DinnerPat Shieldshttp://www.blogger.com/profile/16638967424677722383noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-5657893141930894288.post-32115962755406717822014-11-10T09:21:34.238-08:002014-11-10T09:21:34.238-08:00Pat: The shroud you mentioned improves efficiency...Pat: The shroud you mentioned improves efficiency, but is not absolutely essential. We are dealing with multiple issues with these thermo-electric devices. Small amounts of power are generated and it must overcome friction and mechanical inertia of the blades. In order to move air, the blades also must have an angle of attack. Imagine completely flat blades that would fit on a dish. Rotation would produce no forward or backward air movement, just turbulence. When you add the blade angle to move air, you require more energy. Another factor is that the hot stove surface produces a convection current that sends the air up (i.e. vertical) In the particular case you observed, the air flow off the fan might be 'swallowed' up by the vertical convection current so that you sense no flow when you put your hand in front or behind it. If that is the case, you are just looking at a toy, like an indoor whirli-gig. <bbbbhttps://www.blogger.com/profile/06572246640405502640noreply@blogger.com