What would happen to your unprotected body in outer space?

neil wrote:

Some dictionaries and text books not withstanding, IMHO, convection is heat tranfer by movement of matteris too broad a defintion, otherwuise moving my warm food from my plate to my mouth is covection. Neil

Frankly, I wish this dispute could have simply been dropped, but since you raise it again, the term "convection" is already in use in Physics, and we are not free to redefine it.

From: http://www.cecs.pdx.edu/~sailor/Courses/ME323_W2004/lecture1.htm

Quote:

CONVECTION:

This mode of heat transfer between a solid surface and an adjacent fluid includes two components: (a) energy transport associated with molecular motion and (b) energy transfer associated with bulk fluid motion. The first component is analogous to conduction of heat (diffusion) in a solid. The second is advective heat transfer that can only result in a fluid.

There are two types of convection:

1. forced convection - the flow is caused by an external means such as a fan.

2. free (natural) convection - the flow is caused by buoyancy forces resulting from density differences that arise from temperature variations within the fluid.

In some of the most common cases, it functions more effectively with gravity, but as a general phenomenon in Physics, it is not related to gravity. And it certainly is not dependent on the gradient of the field, which, contrary to the use of the word in English, is defined as the rate of change of field strength with distance. The original situation described in the post that started the thread did not deal with heat transfer in an air filled room, but rather to and from an isolated body in space.

And yes, I have worked professionally in the field of heat transfer, in both theory and experiment (for Westinghouse Electric in the 80s).

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Hot lava flowing down hill is natural, Is that heat transfer by movement of matter? How about a mouse running across the floor? His body temperature is about 100 degrees f. If we wish to define convection as all heat movement that is not radiation or conduction then our sun is convecting heat as it orbits our galaxy. Neil

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neil wrote:

Hot lava flowing down hill is natural, Is that heat transfer by movement of matter? How about a mouse running across the floor? His body temperature is about 100 degrees f. If we wish to define convection as all heat movement that is not radiation or conduction then our sun is convecting heat as it orbits our galaxy. Neil

Well, first of all, Neil, we aren't free to define it, since it is already in use in physics. It would be counterproductive to redefine a scientific term already in use.

Secondly, the examples you gave would certainly not correspond to what anyone actually means by convection. However, what I had been trying originally to say, many many posts ago, was that one very small source of eat loss for a body in space might be fluids boiling off the body, e.g. the tongue, because of the presence of vacuum. I am sure you've noticed that when you step out of a shower, you sometimes feel cold, because evaporating water is carrying heat away from your body.

In the field of heat transfer, one says that there are three, and only three, methods of heat transfer: conduction, radiation, and convection. Clearly the loss off heat through evaporating liquid is not conduction or radiation. Convection is generally defined as heat transfer through the actual motion of matter which contains heat. Hence my use of the term convection.

Clearly, if a human being were to be released in space, the primary method of heat loss would be radiation.

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Brandon9000 wrote:

Frankly, I wish this dispute could have simply been dropped...

Dropped huh ?
I'm not surprised.
Often the way when you can't prove a thing.
Perhaps it'll all just go away and the laws of the universe will conform to your own internal worldview and stop paying attention to experiment and observation.

I wish you luck.

Quote:

And yes, I have worked professionally in the field of heat transfer, in both theory and experiment (for Westinghouse Electric in the 80s).

No comment.
*smirk*

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Heliotrope wrote:

Brandon9000 wrote:
Frankly, I wish this dispute could have simply been dropped...

Dropped huh ?
I'm not surprised.
Often the way when you can't prove a thing.
Perhaps it'll all just go away and the laws of the universe will conform to your own internal worldview and stop paying attention to experiment and observation.

I wish you luck.

Quote:
And yes, I have worked professionally in the field of heat transfer, in both theory and experiment (for Westinghouse Electric in the 80s).

No comment.
*smirk*

The classic form of someone who has failed in arguing the actual topic.

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I think not.

You have presented not one single shred of evidence to support your position.
I have supplied reasoned argument replete with the facts and have supplied plenty of references.

The ball is in your court.
Prove me and the ENTIRE scientific community wrong.

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Heliotrope wrote:

I think not.

You have presented not one single shred of evidence to support your position.
I have supplied reasoned argument replete with the facts and have supplied plenty of references.

The ball is in your court.
Prove me and the ENTIRE scientific community wrong.

The "entire scientific community," huh? That's your story. I haven't seen their posts here.

I've supplied lots of evidence, and a number of references. But we can go through it again if you like.

Heliotrope wrote:

Heat transfer by conduction does indeed occur.

Conduction to what? The body is floating in space.

Heliotrope wrote:

It is only convection that is prevented because there is no gravity gradient.

1. You are misusing the word gradient. In your subsequent posts, your argument was clearly that convection requires gravity, not a gravity gradient. You had clearly been unaware that gradient in physics means the rate of change of field intensity with position.

2. Your references to fluid dynamics in a room are irrelevant because the discussion related to a body floating in space. Your comment about gravity is misguided anyway. The real factor minimizing convection in this situation is the fact that there is no fluid external to the body to carry heat away. Clearly, though, the body could lose tiny amounts of heat by having fluids such as saliva boil away - not a significant source of heat transfer, but the process does occur. As I mentioned to Neil, the evaporation of fluids from the body is why one often feels cold upon stepping out of the shower. And that sure isn't conduction or radiation. And even taking your own example of convection in a room, it operates poorly, but is still present in the absence of gravity. And, you yourself admit that with the addition of air moving mechanisms, convection is not only present but efficient, which constitutes.......convection in the absence of gravity.

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I am challanged by absolute words such as heat is transfered ONLY by conduction, convection and radiation. Two thermocouples at the ends of a mile long wire send heat over the mile by electric curent which I guess must be convection, or electrical conduction. I really think ONLY is a nonsence. Neil

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neil wrote:

I am challanged by absolute words such as heat is transfered ONLY by conduction, convection and radiation. Two thermocouples at the ends of a mile long wire send heat over the mile by electric curent which I guess must be convection, or electrical conduction. I really think ONLY is a nonsence. Neil

Hi, Neil. I am not sure that I completely have the picture of the experiment you are describing, but if you take a thermocouple and heat one end, you will produce a voltage which can be measured at the other end. If you then connnect the output to a mile long pair of wires, and at the remote end convert the electric curent back into heat, it was electricity that you transmitted, not heat. If this is an accurate picture of what you are describing, then it is about the same as making a phone call. You speak into one phone, and the voice somes out of another phone, perhaps very far away. Yet it was electricity that was transmitted, not sound, although it was ultimately converted back into sound. If I have misunderstood the setup with the thermocouples, please correct me.

If you look up heat transfer in any book, or on any Web site, I believe they will all describe heat transfer as occurring by conduction, radiation, or convection. I don't think you will find a different story anywhere. There is a lot of information available about this.

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Brandon what is so disappointing today is that most people think science is just like anything else, just a matter of opinion.

If someone believes heat travels by some transport mechanism other than convection conduction or radiation, let us call it Thermal Conviction, then its no use arguing because his conviction is just as valid as your convection, or so he thinks.

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On the original question. Wouldn't the "explosions" happen on the cellular level?

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Wilso wrote:

On the original question. Wouldn't the "explosions" happen on the cellular level?

Somewhere back earlier in the thread, I posted NASA's take on it. They say no.

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What would happen to your unprotected body in outer space?

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