Recent content by Paul Arthur

Thanks, and I'm going to go think about this and explore some other options. Thanks for everyone's input.

Hi George, Did you mean this: “I'd suggest heat pickup from condensation of water vapor in 30degC air at 50%RH at the air - cold water interface be estimated by assuming a cross current of say 5mm depth of 0.5m/sec of warm air, which goes from 30degC, 50% RH to 20degC, 50% RH at the other end...

Agreed, but how do you calculate that I wonder?

Guys, Surface loads! Should be way easier. Here are my thoughts on the exchange of heat between the water and air. Evaporation Water at 10degC has a saturated water vapour pressure of 1227 N/sqm Air at 30degC 50% rh has a vapour water pressure of 2167 N/sqm Evaporation is therefore zero...

LittleInch [bigsmile] I agree! IRStuff To quote you "I would use 350W, since that's supposedly the maximum sustainable power for a 30-minute duration" How does that relate to the two options I have presented?

A ran the numbers using the total skin resistance and got the following results: Works out to be less than the Mass method I posted earlier. I need a calculation for different water temperatures so can't just use a single figure of say 350W. The mass calc is more conservative @ 321W average...

On further investigation, I found a thermal model in this paper P3, which tries to work out survivability in cold water. https://www.worldscientific.com/doi/pdf/10.4015/S1016237205000251?download=true Anyone have a view on this approach? Worth doing some sums I think?

It seems I’m not the only one who is interested in heat loss from a human in cold water! https://physics.stackexchange.com/questions/371642/heat-loss-through-skin-into-water In that post they use the simple equation H=K⋅A⋅ΔT/Δx, where: H is heat loss, K is the thermal conductivity of skin...

Hi George, Good to hear Bexley is still performing!

All interesting points IRstuff but, we don’t have the answers to what you have quoted. I’m not convinced a suitable heat transfer coefficient of a cooling body to water exists. Also I’m not trying to simulate the body cooling as it will but, the body will start to react and produce more energy...

Thanks, I'm well known here so removing the country also would help keep my anonymity. Air to water tomorrow!

Hi Dave, Not worried, I don't work for that company, I own it [bigsmile]. I would appreciate it if you would remove the company name though and I'll do the same. I'm always questioning what I do and exploring what others might think and some would say, I'm not your ordinary engineer! I'll turn...

But where did you come up with S + A? Sounds like you are stalking me [lol] That's why I just changed my user name [bigsmile]

Hey 3DDave, No, I don't work for them but why do you ask? Paul

Hi Guys, This is not going to be perfect, as expected, but I think is as good as I'm going to get re bather cooling loads. It's based on mass as my previous post. It assumes the bather is in for a short 3 mins and then gets out, heats back up and then gets back in after 3 mins. Typical of use...