Heat loss question.

[bigburner]

Here's the deal. Went around today with IR thermometer and flat black spray paint and checked about 50 locations, any way from one building to another I have 2 one inch pex inside a 3" piece of armor flex [not separated] inside a 4 inch ADS pipe.

This particular run is 300ft. I estimate the GPM at about 4 -maybe -5.

water leaving building A is 134 & water returning to building A is 130 -- water entering building B is 130 & water leaving building B is 126

I can't rap my head around what the actual temperature loss is. Do Ya- average?? Obviously there is some heat transfer here, math & typing not my stronger points

 

[Sawyer]

I have flow from the boiler to two different locations. I calculate the delta T on each zone separately.

Is your line 300ft loop or one way, 600’ loop?

 

[bigburner]

This is just one of the loops -it's three hundred one way. I am sure it's a simple equation, just can't picture it. just trying to figure out is the under ground loss, but got to know the split.

 

[jimbom]

If I understand your post, the heal loss (BTU/hour) = (5gpm*60min/hour*8.34lbm of water/gallon)*(1BTU/lbm-F)*(134 F-130 F)
Or about 10,000BTU/hour.

 

[jimbom]

That was for building A. The heat loss for building B would be the same, assuming the flow and temperature drop are the same.

 

[bigburner]

I am not trying to figure loads,only the under ground load/loss. I measured the pipe where it entered the ground and where it came out at each end. if you average them u get 4 degree loss, but if you lose 4 degrees on one and gain it on the other, isn't that zero!

 

[jimbom]

[quote author="bigburner" date="1295841938"]Here's the deal. Went around today with IR thermometer and flat black spray paint and checked about 50 locations, any way from one building to another I have 2 one inch pex inside a 3" piece of armor flex [not separated] inside a 4 inch ADS pipe.

This particular run is 300ft. I estimate the GPM at about 4 -maybe -5.

water leaving building A is 134 & water returning to building A is 130 -- water entering building B is 130 & water leaving building B is 126

Trying to figure things without drawings. A 5 gpm flow that drops 4 F between two points has a heat loss of 10,000BTU/hour between those two points.

I probably read your post wrong, but it looked like building A out and return had a 4 F drop(134-130) in temperature. It looked like building B in and exit had a 4 F drop(130-126).

Did I understand the question? If not try me again. I'm kind of old so sometimes it takes me a couple of passes.

 

[ewdudley]

I am not trying to figure loads,only the under ground load/loss. I measured the pipe where it entered the ground and where it came out at each end. if you average them u get 4 degree loss, but if you lose 4 degrees on one and gain it on the other, isn't that zero!

Right, with the numbers you've given the heat loss to the ground is zero. Points B see a heat gain of GPM * 4 * 500 and points A see a heat loss of GPM * 4 * 500, which says the flux of heat leaving A is exactly the amount being left behind at B, so there's no heat that could have gone into the ground.

By coincidence the flow of heat from the supply pipe to the return pipe is also GPM * 4 * 500.

To measure heat loss to the ground you'd need more accurate simultaneous temperature measurements, and several dozen of them over time.

--ewd

 

[Sawyer]

"water leaving building A is 134 & water returning to building A is 130—water entering building B is 130 & water leaving building B is 126"

Is building A your boiler room and building B your house or load? or do you have two supply/return lines from your boiler, one each for building A and building B?

 

[heaterman]

You will be soaking a little heat from your supply tube to the return if they are both in the same conduit. Have you checked temp diff supply/return at building B?