delta-t w hx

[flyingcow]

If I understand what delta-t is. The difference between supply and return?


I've got 170/164/154 in my tank. My supply line feeding it is about 195(just a shade under,and its crept up to 200 occasionly) and the return out of the tank is 160. Pretty good isn't it? Seems like the hx is doing its job.

When the tank was about 135/128/120 i was getting 200 in and 140. i didn't write this one down, but its close.

Any thoughts?

 

[stee6043]

"Delta T" is just a fancy way to say "change in temperature".

I'm confused by your statement above though. You mention tank temps, supply line, and "return out of the tank" all in the same sentence. Nonetheless, you'll see varying opinions on what the "best" setup is with regards to HX performance. For me I get the best performance/efficiency by maximizing the change in temp through my HX. When my tanks and boiler are up to temp I run a supply temp of 170-180 or so and return temps of 110-115 (just HX temps we're talking). I accomplish this with a variable speed pump and a little "tweaking" with ball valves.

 

[flyingcow]

I've got pasco gauges on supply side and return side on hx(thats submersed in my 820gal tank). About 5ft from coil. So I can read my in and out temps.

 

[in hot water]

The delta t will change a bit depending on the temperatures of the tank. With a cold tank, expect a larger delta t. As the tank warms that delta t may tighten up.

If you had a way to measure the actual flow rate, and knowing the delta t, you could calculate how many btu/ hr you are transfering at any given time.

With water as the transfer fluid Energy transfered = 500 X gpm X (delta T)

So with a 12 gpm flow rate and a 180 in 160 return 500 X 12 X (180-160) = 120,000 BTU/ hour