Heat loss from exposed outdoor pipework

Does anyone know how to work out what the heat loss would be from say a 20mm section of exposed 28mm copper pipe outside say at 0C and 8C at a given flow temp?
There are a couple of valves and a bit of pipe where there is a gap in the insulation on our system and I want to know how much of a loss that would be creating.
I am planning to do something about it it’s just very hard to reach without pulling the unit forward so isn’t going to be fun.

This is next to impossible, Andrew, as it would hugely depend on wind speed, whether the uninsulated pipework is wet, and the transmissivity of the air (effectively, the air humidity).

I measured a huge heat loss between my ASHP and my indoor buffer tank, even with 98% of the pipe run well insulated (about 0.5degC in each direction, or over 1kW for each of supply and return lines) when it was recently very cold (-2degC) and windy (force 5) outside.



Not sure how effective they are, but I got these to cover over the valves and they can be easily removed as they are closed using velcro.

Outdoor Faucet Antifreeze Cover Leather Protector For Garden - Temu United Kingdom

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