Model vertical helical ground heat exchanger in EnergyPlus

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@JKavanaugh The picture is in the post is actually from the experiment. You can see the complex where out lab is located in the background. If memory serves correctly, I think they were around 5m long. Some of the holes may have been different lengths too. I wasn't involved in this project until now. Anyway, thanks for replying, but those won't work. Modeling of ground heat exchangers is not a trivial problem. I expect the pond model to be way too good of a heat exchanger compared to dirt, and we don't know what temperature the pond should be.

The pond model should take temperature fluctuation of the pond water into account, much like the ground temperature variations of your charts. You are correct in that water would be a much better heat exchanger, but the model may allow you to make the thermal capacity of water much worse by changing the pond area and depth. The pond or slinky model are not ideal for your situation, but they are the closest analogs to what is currently available in E+. I don't think you're going to get any better results trying to manipulate the vertical U-tube model.

From the E+ reference on the Slinky model:

"This model reuses much of the same code including the load aggregation and temperature response caluclations which are described above in the GroundHeatExchanger:Vertical model. As a result, that section can also be used as reference material. This model is unique in that it generates it’s own temperature response factor g-functions, rather than relying on the other software or data to generate the g-functions."

@JKavanaugh I know you're trying to be helpful, but these models are fundamentally different. The temperature of the dirt varies vertically and radially for the U-tube, but I suspect all the water in the pond is at the same temperature. Yes, any ground heat exchanger model will approximate every ground heat exchanger, but we can't publish that. Just ask yourself, "If you read a research paper where experimental data from an actual U-tube ground heat exchanger was said to be equivalent with a modeled pond heat exchanger, would you make financial decisions based on the results?" No.

I'm confused, I thought your experimental data comes from the helical heat exchanger shown in the photo, is that not the situation?

The point I'm trying to make is that I would think that actual operation of a helical heat exchanger with borehole depths of 5m would be closer to the E+ model of a pond or slinky heat exchanger, rather than the E+ model of a vertical U-tube. The helical exchanger will be effected by annual fluctuations in the ground temperature in the relatively shallow ground in much the same way a pond or slinky heat exchanger would.

@anchapin
1) The slinky is a way different model from a vertical bore. It just won't work.
2) We do have the correct response factors for calculating the borehole wall temperature, but the problem lies with the C code then using a finite element method to calculate the heat distribution in the grout for the purpose of determining the grout U-tube boundary temperature. The helix is pretty much against the borehole wall, so that's no good.
3) I expect the pond model to be way too good of a heat exchanger compared to dirt, and we don't know what temperature the pond should be.