Wind chill

Discussion in 'Motorhome Chat' started by Touchwood, Feb 27, 2012.

  1. Touchwood

    Touchwood Funster

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    Reading February's Practical Motorhome, I came across the following from "Diamond Dave" in the technical advice section.

    "Take water tanks, for example. They're often underslung and if you're driving at 60mph, there's going to be a 60mph gale blowing along the underside of your 'van. This will create a significant wind chill factor and if the ambient temperature is low - say, around 5 deg. C - then the tanks and pipework will be subjected to a sub-zero blast that can cause water to freeze.

    The solution is to insulate the tanks and pipework:...."


    I'm don't wish to impugn Diamond Dave's technical expertise in other areas, but this is nonsense, and a commonly held misconception. Wind chill factor only affects bodies with their own heat source which keeps them above the air temperature (like warm blooded mammals such as you or I)

    It is true that the air velocity will cause a greater rate of heat loss, but only until the temperature of the water tank has dropped to that of the surrounding air. Once the temperatures are equal, there is no temperature gradient and heat will cease to flow.

    There may well be other perfectly valid reasons for insulating your underslung tanks and pipework, but wind chill isn't one of them.
     
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  2. scotjimland

    scotjimland Funster Life Member

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    As you say, just a load of bollox from an 'expert' :RollEyes:
     
  3. Reallyretired

    Reallyretired Funster

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    Obviously actually knowing anything about a subject should not be a prerequisite to writing an advice column.
    I would be very dubious about any of his advice however following this, but as I don't subscribe to this mag I probably won't have the opportunity.:Smile:
     
  4. slobadoberbob

    slobadoberbob Read Only Funster

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    sums it up Jim

    Just about sums it up Jim:Rofl1::Rofl1::Rofl1::Rofl1:


    Bob
     
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  5. Stephen & Jeannie

    Stephen & Jeannie Read Only Funster

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    Oh ye of little faith !!!

    I presume that you posters don't realise that "Diamond Dave" is none other than our own much revered Dave Newell of Telford who has on numerous occasions helped out many of us when in need !:thumb:
    When I get back to the UK in June, my first stop will be to his workshop for a service and a habitation check !! And not at rip off prices like some pseudo MH establishments !:Doh:
    AND he gives Funsters a discount !:youbetcha:
    This bugger Dave knows what he is talking about in my humble opinion !:Cool::Cool::Cool:
     
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  6. icantremember

    icantremember Funster

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    .....and of course the definition of an expert is-


    "ex" = a hasbeen and
    s"purt" = a drip under pressure :RollEyes:
     
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  7. Stephen & Jeannie

    Stephen & Jeannie Read Only Funster

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    You are all very quick with your knocking posts aren't you !:Angry:
    Let's hope you don't need any help in the future !
     
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  8. scotjimland

    scotjimland Funster Life Member

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    Had no idea Steve .. but it's still wrong..

    I'm sure Dave is a good vehicle and motorhome mechanic, and from the Funsters reviews gives a top notch job.. at a decent price..

    Thermodynamics should be left the scientists :Wink:
     
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  9. Forestboy

    Forestboy Funster Life Member

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    Hear Hear

    :thumb::thumb:
     
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  10. Touchwood

    Touchwood Funster

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    I was careful to say in the OP that I wasn't doubting Dave's credentials in other areas - anyone can be wrong (I've even been known to be wrong meself on occasion)

    I was merely pointing out that in this case he is undoubtedly in error - I also stated that it is a commonly held misconception - in other words an easy mistake to make. I don't make a habit of correcting other people's errors, but I felt on this occasion his advice could lead to unnecessary work and expense.

    If others choose to interpret this instance as evidence of the general fallibility of "experts" that's hardly my fault.
     
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  11. madbluemad

    madbluemad

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    Is this really Dave Newell or are you avin a laff. :Rofl1::Rofl1::Rofl1::Rofl1::Rofl1:
    Jim
    :Laughing:
     
  12. madbluemad

    madbluemad

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    If it is Dave Newell, I demand a recount on the basis of it was a "sting" guvnor.
    Jim
    :Rofl1::Rofl1::Rofl1::Rofl1:
     
  13. Stephen & Jeannie

    Stephen & Jeannie Read Only Funster

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    Your post was NOT one of the knocking posts !
     
  14. JeanLuc

    JeanLuc Funster

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    When we first got into motorhoming in late 2006 and were looking around for information before buying, Diamond Dave Newell's articles were a source of help and good advice. In fact, I clipped and kept several of them for some time.
    Having spoken to Dave on a few occasions, and had work done by him in Telford, I can only support the view that he is a very experienced and moreover, very helpful chap. I have never failed to get good advice and would recommend him to anyone looking for a first class motorhome engineer.
    I agree that the OP was not posting knocking copy, but was seeking to enlighten and I, for one, have learnt a bit about thermodynamics today - but I still think Dave's a Diamond!
     
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  15. Gromett

    Gromett Funster

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    Nice post :) I had never even considered wind chill as a factor in water freezing lol...

    I did however have to do some research on water freezing this winter and found something out that I thought was interesting.

    Water freezes at 0 and melts at 0. How does it decide what to do :Rofl1:

    At 0 degrees water will begin to freeze. The whole body of water will stay at 0 degrees until it is all frozen then it will start falling again to the ambient.

    the same goes in reverse. at 0.1C water will start melting. Even if the exterior temperature gets to 10C the water will stay at 0C until it is all melted.

    Finally (remembered from physics lessons) If warm water rises to the surface and cold water sinks. How come ice forms on the top.
    Water has a unique property in that at 4C it becomes less dense and floats to the top. The warmest part of a pond in winter will be at the bottom which is why the fish all congregate there :thumb:. So if you fall in head to the bottom, you may not be able to breath but you will be warmer :Rofl1:
     
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  16. Touchwood

    Touchwood Funster

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    It's all to do with latent and sensible heat. Sensible heat is the heat energy which changes the temperature of a substance - in the case of water it's approximately 4.2 kJ per kg for every degree change in temperature. so a 1 kg mass of water cooling from 1 deg. C to 0 deg. C loses 4.2 kJ of heat energy.

    Latent heat is the heat needed to change the state of the water - from water to ice for example - and this is a much bigger amount. To change 1 kg of water to 1 kg of ice needs a loss of 334 kJ - about 80 times as much energy as it takes to cool the same amount through 1 deg. C change in temperature.

    The density change at 4 deg. C is a remarkable phenomenon - it if weren't for this fortuitous fact there would be no possibility of life surviving in water in colder climes, as any body of water would freeze from the bottom up and become a solid block of ice. As it is the ice forms on the top and effectively insulates the body of water thus slowing down the freezing of the lower levels. It's arguable that life on earth couldn't have developed if it weren't for this.

    Fascinating stuff, science :BigGrin:
     
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  17. Gromett

    Gromett Funster

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  18. dave newell lvs

    dave newell lvs Trader-Vehicle Services

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    My thanks to Touchwood for politely pointing this out, I was wrong, simple as that. To all the other posters knocking all I can say is I actually don't really care very much what you think of me:Wink: but I would suggest people think a little before posting nasty comments. My thanks to those who posted in a positive light for me.

    I will correct my error in another issue.

    Cheers all. D.
     
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  19. scotjimland

    scotjimland Funster Life Member

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    well, must be mine.. :RollEyes:

    I make no apology, if I read something I know is wrong, I'll say so .. no matter who writes it.

    If that's knocking.. so be it.
     
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  20. dave newell lvs

    dave newell lvs Trader-Vehicle Services

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    So nice of you to say so Jim.

    "As you say, just a load of bollox from an 'expert'"

    I do find this a bit offensive to be honest, what say you?

    D.
     
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