45 is the cool temp so they could send the community a higher temp water to their heat exchanger?
Then 45 or below is sent back on the return.
45 is the cool temp so they could send the community a higher temp water to their heat exchanger?
Then 45 or below is sent back on the return.
Yes, but the heat will still likely need boosting by about a further 10 degrees either at the source or end user.
DC inlet is 45°C, outlet is 55°C assuming a 10°C ΔT. By the time that's travelled 500m–1km through pipework you've lost a few degrees, so you're arriving at the HIU at maybe 50–52°C. The home radiator circuit then takes that down by around say 12°C, returning ~38°C. Factor in pipe losses on the return leg and you're back at the data centre with maybe 35°C inlet rather than 45°C — meaning the DC output is now only 45°C rather than 55°C, and the whole system gradually degrades each cycle. You could address this by mixing some hot output back into the return to keep the DC inlet stable at 45°C, but eh.
> By the time that's travelled 500m–1km through pipework you've lost a few degrees
you'd be surprised. If you have high flow, and the pipes are insulated and underground, then after about a week the temperature drop isn't that much. You do have heat losses, but if you have a high enough continuos flow and a big enough pipe, then it'll be low enough to not worry about, especially if the aim is heat shedding rather than efficiency.
My old flat was powered by both the 1970s boilers across the way, and more recently the massive south london incinerator. The pipe cross section was I think 40cm and at peak carried ~3-5 Megawatts of heat. I think it operated at 150c, but that could be me misremembering (this is the later version of the network: https://www.burohappold.com/projects/veolia-southwark-2-0-he... for the councils is they get a maintained heater network, which is much cheaper than doing it themselves (even more now with gas being so expensive) the power station gets to charge for a waste product and it doubles their on paper efficiency, its a win win.)
Yeah, I mean it does depend on the pipework and season/geography for sure. I was simplifying a bit in that a part of the 'distribution' losses are in the plate heat exchanger as you convert from the "IT" loop to the "district heating" loop. The numbers are roughly right, potentially slightly worse in deep winter when it matters the most.
>Factor in pipe losses on the return leg and you're back at the data centre with maybe 35°C inlet rather than 45°C
Surely having the input fluid being colder is a benefit, not a problem? Just run the fluid more slowly through the system?
In essence you can't really because slower flow rate makes the heat transfer less efficient. You'd be halfing the flow rate in that example.
But a larger delta-T makes it more efficient?
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Maybe you can use a heat exchanger, like in nuclear power plants, and separate the data center flow from the outside flow, so they can go at different speeds.
You would use a heat exchanger normally anyway. Forcing the outside (DH) to be slow would get you that, but there is cost in having low flow in that HXs are less efficient at the far end and you can transfer less heat in the same pipework (it would more than half the district heating capacity). So in practice, not really.