[ftp]

Do you find your flow gets restricted the colder it gets? I've had to turn my varistream up a couple of notches since this cold weather.

[clean]

Do you find your flow gets restricted the colder it gets? I've had to turn my varistream up a couple of notches since this cold weather.

Ye i noticed this last year,it`s to do with the water temperature being so cold it`s denser (thicker) 

[NWH]

Heat the van up and close the door to on really cold days,it only seems to do it on bitterly cold days with the doors open.

[michael papworth]

Hiyya Pole King. Yes, you've got exactly the right idea. It's not actually density. It's viscosity.

The viscosity of water increses by about 30% for each 10 degrees drop in temperature. So as the water gets colder, it does indeed get "thicker".

This is what viscosity is, taken from wikipedia:

In general terms it is the resistance of a liquid to flow, or its "thickness". Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction. Thus, water is "thin", having a lower viscosity, while vegetable oil is "thick" having a higher viscosity.

The effect is VERY noticeable in your RO unit which is slower with colder water.

[dmlservices]

i have noticed water sheets down glass better on cold days,perhaps because it it 'thicker' it it also slghltly heavier,

daz

[scud]

  It wont be any heavier, ice is actually lighter than the equivilant volume of water.

[dmlservices]

  It wont be any heavier, ice is actually lighter than the equivilant volume of water.

thats because water expands as it freezes,

but for some reason water heets down glass better when its really cold,

anyone else noticed this ?

daz

[scud]

  I know water expands as it freezes, but it cannot get any heavier just because it is colder, its density does not change.

  As for the sheeting when colder, can't say I have noticed or have an answer as to why.

[michael papworth]

I love this stuff!

Scud is wrong. (Sorry!!) Water is actually at its greatest density at about 4^oC. It is this (as well as the HUGE latent heat of crystallisation)  which makes it very difficult for lakes to freeze completely even in the coldest weather.

I don't know what happens to the viscosity in this temperature range.

The factor affecting the sheeting/beading tendency of the water is the surface tension. Here again I have no idea what happens in this temperature range.

We have THREE different properties to consider: viscosity, density and surface tension.

I think it would be very difficult to make any predictions. Experience is the best guide here.

[scud]

  wally, are you my wife?

  Mind you, she doesn't apologise when she tells me I am wrong.

[michael papworth]

Hi Scud.

One of the most famous Zen koans is the question, “If a tree falls in the forest and there’s nobody there to hear it, does it make a sound?

My own version of this is: "If a man performs an action and there is no woman there to observe it, is he still wrong?"

Er. No. I'm not your wife.

[dmlservices]

i think there is still a lot to learn , with regards to the way water behaves under different conditions,

and also if pure water behaves any differently, i heard it has a slightly higher boiling point.


daz

[ftp]

I found one thing out today - cold weather stiffens your microbore - how do i know?
I got smacked in the head by my easi snap end connector as the last four feet of hose came whizzing in. 

[dmlservices]

ouch .

daz

[scud]

I found one thing out today - cold weather stiffens your microbore - how do i know?
I got smacked in the head by my easi snap end connector as the last four feet of hose came whizzing in. 

  Thats a daily occurance here! Find its worse in the warm when the hose whips a bit and picks up more speed!

  One thing I do know about pure water - it doesn't conduct electricity.

[michael papworth]

Yes, dmlservices. You're absolutely right. And with there being so many variables (viscosity, density and surface tension against temperature) the analysis would be horrendous.

Just as a point of interest:

* one variable against temperature would give you a line graph - 2-dimensions.

* two variables against temperature would give you a surface graph - 3-dimensions.

* three variables against temperature would give you a graph that you couldn't draw or even imagine - 4-dimensions. Although you could construct an empirical/experimental/mathematical model, you couldn't say what it looks like!

And no. Pure water boils at 100^oC.

And I can sympathise with ftp. I nearly soiled myself the other day as a similar thing happened and the end connector banged into a conservatory door hitting the glass with a real whack. Luckily, no damage.

And yes, Scud, you're right about the very low conductivity of pure water. It is completely deionised, and it's the ions in impure water that conduct the electricity, not the water. No ions => no conductivity.