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What does it take to freeze & crack an engine block?

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Old 05-18-2007, 07:20 AM
  #21
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Originally Posted by BBB725 View Post
Wind chill, yes it can happen
Wind chill is a human factor. It has nothing to do with non-living objects. The minimum air temperature is the lowest temperature the engines would achieve.

If the boat were travelling down the hi-way, air moving across the engines from the vents would accelerate the heat transfer through convection. They would never drop below ambient (30F). To tell how long transient heat transfer takes to get the engines to 30F, you need to know the velocity of the air (at 1 atmosphere) moving across the engines. It will be a natural convection type of problem. We also need to know the conduction coefficients of the iron, and convection coefficients of the air (both can be looked up in tables). You could neglect the paint thickness effects on heat transfer as this would be minor. Also need to know the initial temperature of the engines.

Knowing the thickness of the block or head wall will give us the time that the INSIDE wall of the piece will reach 30F. From there, we still need to calculate how long it will take the water to freeze at 32F. That becomes a thermodynamics problem that we will need to develop equations of state as there are phase changes in the water (liquid to solid).

That said, we can spend a lengthy amount of time gathering info and doing calculations... I think the boat sat outside for a lengthy period of time. Someone is not being a "straight shooter"
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Old 05-18-2007, 07:23 AM
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I know a couple people have claimed to have it happen to them or a friend but, no offense, I call BS on this one. There is a certain amount of latent heat even in those cold ass iron engine blocks. The temp usually has to be at or below freezing for an extended period to actually crack a block. And, as someone else also said, the engine compartment offers some insulation from the elements too.

As far as wind chill, that is correct. It only has effect on living tissue. And, the air isn't actually colder, it only "feels" colder to your skin. The ambient temp is actually the same.
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Old 05-18-2007, 07:30 AM
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Quote:
Originally Posted by SPITFIRE View Post
I thought wind chill only had effect on living tissue??
True...to a point.

In an active thermodynamic system (active meaning there exists heat flux - a transfer of heat at some rate), moving air will have some effect. With inanimate objects that don't produce their own heat and the system is stabilized, wind will not have any effect. In other words, if it's 30 degrees outside and the engine block is already stable at 30 degrees there will be no effect of wind. 30 degrees is 30 degrees no matter if the air is still or moving --- Now, if the engine block is at 40 degrees and it's 30 degrees outside, in still air the block will cool down to 30 at a given rate until it stabilizes at 30 degrees depending on the air's ability to absorb heat. The air immediately surrounding the block gains heat and warms slightly (this slows heat transfer because the temp difference is diminished) and it thus transfers this heat slowly to the air further and further away. Now, if this the air is moving swiftly past the block and it's at 30 degrees, the air immediately in contact with the block is always at 30 degrees (no warming effect), and it will absorb heat more quickly than if it were still.

When weather people speak of 'wind chill' it does not apply to objects that do not create their own heat. It's strictly an approximate measure of how 'cold' it will 'feel' to humans with a body temp of 98.6. Say for instance, if 30 degree air is moving at 20 mph past your body, it will absorb heat away from you at an increased rate approximately equal to still air that's perhaps at 0 degrees. For an object that does not make its own heat and it's already the same temperature as the surrounding air, wind chill does not apply.


Back to the original question: I can't possibly see how a block can freeze over the course of 4 hours in 30 degree temperatures. Think of how long it takes to freeze an ice cube in your freezer which is typically about 0 degrees and the water is in direct contact with this cold air. I call B.S.
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Old 05-18-2007, 07:31 AM
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Originally Posted by SPITFIRE View Post
I thought wind chill only had effect on living tissue??
Right, If it's 35 degrees and the wind is blowing 30 miles an hour that doesn't mean water will freeze. Wind chill is the feeling on your skin. I don't believe it would freeze.
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Old 05-18-2007, 07:34 AM
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Quote:
Originally Posted by razor1115 View Post
Wind chill is a human factor. It has nothing to do with non-living objects. The minimum air temperature is the lowest temperature the engines would achieve.

If the boat were travelling down the hi-way, air moving across the engines from the vents would accelerate the heat transfer through convection. They would never drop below ambient (30F). To tell how long transient heat transfer takes to get the engines to 30F, you need to know the velocity of the air (at 1 atmosphere) moving across the engines. It will be a natural convection type of problem. We also need to know the conduction coefficients of the iron, and convection coefficients of the air (both can be looked up in tables). You could neglect the paint thickness effects on heat transfer as this would be minor. Also need to know the initial temperature of the engines.

Knowing the thickness of the block or head wall will give us the time that the INSIDE wall of the piece will reach 30F. From there, we still need to calculate how long it will take the water to freeze at 32F. That becomes a thermodynamics problem that we will need to develop equations of state as there are phase changes in the water (liquid to solid).

That said, we can spend a lengthy amount of time gathering info and doing calculations... I think the boat sat outside for a lengthy period of time. Someone is not being a "straight shooter"
That's amazing, That was my thoughts exactly! I was going to explain it the same way I just thought most of the other members wouldn't understand. This just confirmed my initial hypothasis. Thank you!
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Old 05-18-2007, 07:45 AM
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My "rule of thumb" is...

It takes 24 degrees for 24 hours to crack a block. I call BS on someone.

Like others have said, wind chill only affects warm blooded living creatures, not engine blocks.

Sorry to hear that you have a friend!
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Old 05-18-2007, 08:15 AM
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The boat definately sat outside for a while. When I lived in Syracuse, I used to keep my Formula on my boat hoist into early December (or until the weather was forecasting really cold 20 degree weather). There were several times that the temperature dropped below freezing before I could pull the boat out, and I never had a problem. The boat had to sit for an extended time in very cold weather for everything to crack like that.
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Old 05-18-2007, 08:26 AM
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Assuming the boat was in 60 degree or more weather prior to leaving the south, the engine blocks, crank, etc would hold the heat for at least 24 hours. Until the internals reach 30 degrees the water will not freeze solid even if it is pure fresh water. If it has any impurities or salt it will not freeze solid until 28 degrees or below. Up here in MD we rarely see cracked blocks unless the temps stay below 30 day and night for a least a few days.
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Old 05-18-2007, 08:50 AM
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No way did this happen, I live in upstate NY. The engine compartment is well insulated. covers, padding, fiberglass. Temperature drops have to be for an extended period of time and well into the 20's. The aggitation of the water moving as the truck was moving would also slow down the freezing process. Not buying this explanation. The blocks were cracked before the transport. I call BS
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Old 05-18-2007, 09:09 AM
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Quote:
Originally Posted by Clay Washington View Post
My "rule of thumb" is...


Like others have said, wind chill only affects warm blooded living creatures, not engine blocks.


WRONG . Wind chill comes into play on ANYTHING that contains warmth. Shut you car off in a calm 30* night
and a windy 30* night. Restart it 45 mins late. on the windy night the engine temp will have dropped a lot further. Also your home heater will run a lot more on a windy night than a calm night
My bet is the tow person told the storage place he put antifreeze in the engines and they took his word for it. I would have done it myself knowiing it was going north where its cold and NOT depend on anyone else,
That being said , I have backup mechanical temp gauges on my engines that are stainless industrial gauges and have an expanded scale from below freezing to over 250*. after a night in the mid to high 20's both read in the low to mid 40s but this was sitting still with a full cover over the vents.
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Last edited by mopower; 05-18-2007 at 09:16 AM.
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