well i can differentiate between the heat coming from a 700W or 2100 W hot airheater (with a blower) by sensing the temperature difference . I think it can be measured much more accurately with temperature sensors and exact flow measurements. When there is a difference of a factor 3 between the control- and active cell it can be detected.
Peter From: Steve High Sent: Monday, October 13, 2014 3:13 AM To: Vortex Subject: [Vo]:Air Flow Calorimetry Well I spent an hour or so in the HVAC world and sure enough Jed was right. Apparently the standard for measuring air flow in a round duct involves checking wind speed in 18 locations along three separate axes, which is probably not practical when you are trying to assess air flow in a dynamic system. On the other hand I think it is safe to assume that the purveyors of natural gas have worked out a way to know precisely how much petroleum is flowing through their pipes. In the lung doctors office you can blow into a tube that will show precisely how much air your lungs are moving. So if there was a monetary reason to efficiently know how much air is moving through a system we would probably have a reliable means of doing so. On Sun, Oct 12, 2014 at 4:19 PM, Jed Rothwell <javascript-disabled:_e(%7B%7D,'cvml','jedrothw...@gmail.com');> wrote: I have had wretched experiences trying to do air-flow calorimetery. It is done by HVAC installers on a daily basis, so it does work, although I gather it is imprecise. I know it is hard to do right. The hard parts are determining the flow rate of air, and finding the temperature, which varies in the stream even when you go to great lengths to mix the air. - Jed
