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Robl · 02-07-22, 09:05 AM

I found an online manufacturers BPHE calculator tool, here:

https://www.heat-exchangers.uk/online-calculator/

The way you use it is to enter the inlet and outlet temps that you want (all 4 temps), and it then calculates which of their BPHE products could be used. It's a bit frustrating, as clearly they can calculate everything - but only give their parts as an answer. Still, they allow water, and a mix of water&glycol to be used; there's no propane option. When glycol is used, they typically swap their BPHE recommended to a larger one

For example, for water:30% glycol/ 70%water, with a 4C deltaT and 1.8kW transfer, they recommended B5THx16, similar area to the part I've used. Swapping to water:water allows a 3C temp drop to be entered, while they still picked the same part. Their heat exchangers might be better than my cheapie ones, but it holds that using a glycol/water mix means the thermal transfer is worse than with water.

I'll try and measure the deltaT I get for both heat exchangers, and decide if I care enough to upgrade them at some point - there's no rush, it's all working well still.

02-07-22, 09:05 AM	#9
Robl Helper EcoRenovator Join Date: Oct 2020 Location: Cambridge, UK Posts: 31 Thanks: 3 Thanked 27 Times in 14 Posts	I found an online manufacturers BPHE calculator tool, here: https://www.heat-exchangers.uk/online-calculator/ The way you use it is to enter the inlet and outlet temps that you want (all 4 temps), and it then calculates which of their BPHE products could be used. It's a bit frustrating, as clearly they can calculate everything - but only give their parts as an answer. Still, they allow water, and a mix of water&glycol to be used; there's no propane option. When glycol is used, they typically swap their BPHE recommended to a larger one For example, for water:30% glycol/ 70%water, with a 4C deltaT and 1.8kW transfer, they recommended B5THx16, similar area to the part I've used. Swapping to water:water allows a 3C temp drop to be entered, while they still picked the same part. Their heat exchangers might be better than my cheapie ones, but it holds that using a glycol/water mix means the thermal transfer is worse than with water. I'll try and measure the deltaT I get for both heat exchangers, and decide if I care enough to upgrade them at some point - there's no rush, it's all working well still.