230 ATW is generally measured at the wand valve. But between the valve and the jet(s) there is heat loss. That amount of loss varies, depending upon the material of the hose or tube and the thickness of the material, as well as the flow rate through the hose or tube, and it varies with the ambient temperature.
For instance, heat loss will be greater through a stainless steel tube, than a 1/4" hose, due to the tube being "just a tube" and having no insulating value, compared to a hose with several layers that act as insulation.
The longer the fluid stays in the hose or tube (i.e., lower flow rate), the longer the amount of time that it loses temperature to the cooler air around it. The higher the flow rate, the less time to lose heat, therefore less heat loss.
Heat loss is a result of a difference in temperature between two areas, and the two areas coming into a balance by either losing or gaining temperature in the process. (i.e., the cooler air around the hotter tube actually gains temperature, as the hose / tube loses it.)
So, 230 ATW isn't the same thing as 230 ATJ (at the jet)... And 230 ATJ (if it's achieved), isn't the same thing as 230 ATC (at the carpet). At each point along the way, as the solution travels (or if it simply remains in the hose, etc.), it loses temperature.
I haven't done tests to be specific, in terms of what I can say here. But I wouldn't be surprised to see a typical heat loss between the valve and the jets, prior to solution leaving the jets, of 20 degrees, with a stainless steel tube as the conduit. I wouldn't be surprised to see 10 degrees loss with a pressure hose instead of a tube.
So, let's take 10 degrees loss. That means, with a start off point of 230, we now have 220 ATJ. As soon as the solution leaves the jet, it loses temperature. If I remember correctly, SteamWay did a test years ago and the result was that a typical heat loss is 15 degrees per inch of travel, between the jet and the carpet fibers. (And, BTW, that isn't a constant... a smaller jet puts out a smaller stream, which is "thinner", mixes with the surrounding air and loses heat quicker as a result, than a thicker stream does.)
So, if you have 2 inches of travel between the jet and the carpet, you can count on losing 30 degrees there.
230 as a start- off, minus 10 in the tube / hose of the wand, minus 30 between the jet and the fibers... 190 degrees.
... and as soon as the spray hits the fibers, the fibers gain heat, as the spray loses more heat...
That's why I've been "preaching" high heat / high flow systems since the mid- 1990's, when I first began building truck mounts...
High heat gives you a head start... a higher start off point. High flow allows you to retain more of it...
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