On Wed, Jun 22, 2011 at 4:22 PM, Jed Rothwell <[email protected]> wrote:
> ** > Joshua Cude wrote: > > Nope. All you have to know is how dry the steam is, what the temperature >> is, and what the total mass of the steam is. You can derive the steam flow >> rate from that. >> > > Right. But how do you get the total mass of the steam? Even in your > interpretation of what information that device provides, it only gives mass > per unit volume. So you need the volume to get the mass. To get the volume, > you need the flow rate. Infinite loop. It's a rookie mistake, and you're a > seasoned programmer. > > > I repeat: they measure the total mass, separately. They measure the weight > of the water reservoir before and after the test. The mass of water is > starting weight minus ending weight. > I got that. That gives the total mass of the input water. That's the same as the mass of the output water. But the output is a different phase. That means it has a different volume. > The flow rate does not vary significantly with this kind of pump. > I accept that the input flow rate is constant. But the output *volume* flow rate is very different because at least part of the water changes phase. If the meter is giving mass per unit volume of the output, you need to know the *volume* of the output to get the mass of the steam. But you don't know the *volume* of the output steam unless you measure the *output* *volume* flow rate. That RH probe measured directly the wetness of a certain polymer, and relates that to the *density* of water vapor in air. Even if it could give the density of water vapor in steam, we already know that: it's just the density of steam. There are a lot of people interested in the quality (wetness) of steam, and quite elaborate ways to determine it. If it were possible with a simple RH probe, I should think the manufacturers would advertise that as a useful feature of the device. But they don't.
