Heat does not rise...

[vstech]

Originally Posted by funola

Since heat rises, I'd think it's more effective to put the light lower in the engine, like under the oil pan.

Heat does not rise...

[t walgamuth]

Originally Posted by vstech

Heat does not rise...

A factually incomplete statement. True if talking about radiating through metal. If talking about warm air, yes it rises.

[funola]

Originally Posted by vstech

Heat does not rise. heatED air does rise. but heat itself travels to equalized distribution. warm air is not heat.
........

So, a hot air heating system is not heat??? If heat does not rise, why do crock pots have the heating element on the bottom? May as well put the element on the lid?

[85chedeng300D]

Originally Posted by funola

So, a hot air heating system is not heat??? If heat does not rise, why do crock pots have the heating element on the bottom? May as well put the element on the lid?

Yea!!! I completely agree with funola!

Just think about it this way..... try lighting up a candle or a Zippo lighter, then look closely if not obvious.... have you seen a candle or lighter flame going down? even if you flip the candle upside down, the flame will try its best to go up.

So, I'm with funola! I logically conclude that heat rises!

[vstech]

Originally Posted by 85chedeng300D

Yea!!! I completely agree with funola!

Just think about it this way..... try lighting up a candle or a Zippo lighter, then look closely if not obvious.... have you seen a candle or lighter flame going down? even if you flip the candle upside down, the flame will try its best to go up.

So, I'm with funola! I logically conclude that heat rises!

nice conclusions... but wrong.

heat itself does not rise. it's the heated medium that rises.
flame is not heat, it's a plasma of a burning fuel. and yes, in atmosphere, the plasma rises above the source of the fuel due to air lifting it.

in the case of my heater, the shop light, it's mostly radiant energy reflected from the bulb enclosure heating the motor. it would not matter if I pointed it up, down, or sideways... it'd go where it was directed.

anyway, my comment to funola's statement was just to correct an incorrect statement. HEAT does not rise, it's the heated air that rises, also, heated water sort of rises, it more or less radiates from the heat source, but basically rises in a container.

heated metal, obviously does not rise, the heat is absorbed from the point of heat input and radiates towards equal distribution of the energy.

sue me, I'm a HVAC contractor, and little pieces of learning go a long way!

[vstech]

Originally Posted by funola

So, a hot air heating system is not heat??? If heat does not rise, why do crock pots have the heating element on the bottom? May as well put the element on the lid?

... putting the elements in contact with the food being heated is more efficient... it's called conduction! and gravity holds the food in the bottom of the pot... and actually, some crockpots have elements in the bottom, and the side of the pot...

and specifically, a hot air heating system is NOT heat, it's a method of getting heat into a home. the air is heated by passing it through a heated exchanger of some type, and then blown into the home/space to raise the temperature of the space... notice that more than the ceiling is heated...

[funola]

Originally Posted by vstech

... putting the elements in contact with the food being heated is more efficient... it's called conduction! and gravity holds the food in the bottom of the pot... and actually, some crockpots have elements in the bottom, and the side of the pot...

and specifically, a hot air heating system is NOT heat, it's a method of getting heat into a home. the air is heated by passing it through a heated exchanger of some type, and then blown into the home/space to raise the temperature of the space... notice that more than the ceiling is heated...

Anything that get's hot is heat. If you want to play semantics with words that's fine. Heat does rise. It rises in water, not just sort of. If you heat up a pot of water, then put a thermometer at the top and bottom of the pot, the top will measure a higher temp because heat rises. If you heat up a block of metal and measure the top and bottom of the block, the top will be hotter because heat rises. Your head is hotter than your toes because heat rises. The hottest part of the engine is the head because heat rises. Most the heat from the lamp you placed next to the cylinder head is lost to the atmosphere because heat rises. If you install a coolant heater, you'd install it in the lower radiator hose and not in the upper radiator hose because heat rises!

[Brian Carlton]

Originally Posted by funola

If you heat up a block of metal and measure the top and bottom of the block, the top will be hotter because heat rises.

This is the fundamental flaw in your thesis.

If you heat a block of metal, evenly, from all sides (in an oven) and measure the surface temperature of the block, you will find the identical temperature on all surfaces of the block. The heat in the block.........dispersed by conduction through the metal, does not rise.

All of the other examples that you have provided are examples of convection in fluids...........the fluid is in motion. Anytime the fluid is in motion, it will absolutely rise when heated.

You would need to more carefully define "heat" if you want to continue to argue this point with John. What we commonly agree is "heat" is the movement of a fluid.

You may also be familiar with radiant heat. There is no heating of any fluid. Radiant heat will heat a solid that is in the path of the heat. Radiant heat does not give a whit about up or down. The light bulb under the hood of the vehicle does give a fair amount of radiant heat..........360 degrees equally around the bulb (if the bulb is unshielded).

You may be familiar with the sun. The sun can give you a wicked burn via radiant heat. The air temperature adjacent to your skin has not climbed one whit, but you suffer a nasty burn. The radiant heat from the sun has no direction..........it heats evenly via 360 degrees in all axes.

[funola]

Originally Posted by Brian Carlton

....
You would need to more carefully define "heat" if you want to continue to argue this point with John. What we commonly agree is "heat" is the movement of a fluid.
.....

Didn't I say: "If it gets hot, it's heat" ?

[Brian Carlton]

Originally Posted by funola

Didn't I say: "If it gets hot, it's heat" ?

You did, but it's overly simplistic and not something that I would have expected from a rather diligent individual such as yourself.

[vstech]

Originally Posted by funola

Anything that get's hot is heat. If you want to play semantics with words that's fine. Heat does rise. It rises in water, not just sort of. If you heat up a pot of water, then put a thermometer at the top and bottom of the pot, the top will measure a higher temp because heat rises. If you heat up a block of metal and measure the top and bottom of the block, the top will be hotter because heat rises. Your head is hotter than your toes because heat rises. The hottest part of the engine is the head because heat rises. Most the heat from the lamp you placed next to the cylinder head is lost to the atmosphere because heat rises. If you install a coolant heater, you'd install it in the lower radiator hose and not in the upper radiator hose because heat rises!

I am not playing semantics with words.

Heat is a quantity of energy... it's carried in different ways, convection is one of them, and in two of your examples, yes, that heated media rises... air and liquid.
the rest of your statement is incorrect, and actually funny.

[vstech]

Originally Posted by funola

Anything that get's hot is heat. If you heat up a block of metal and measure the top and bottom of the block, the top will be hotter because heat rises.

this is not correct. if you heat a block of metal, it will be hottest in the spot you heated it from, and the temp will drop off in all directions from that point.

[vstech]

Originally Posted by funola

Anything that get's hot is heat. Your head is hotter than your toes because heat rises.

your head is hotter than your toes because you have two major blood vessels pumping blood from your core to the brain, which in the body's opinion is the most important part of your body.

[vstech]

Originally Posted by funola

Anything that get's hot is heat. The hottest part of the engine is the head because heat rises.

the hottest part of the engine during operation of the engine is the prechamber, because it's the part of the engine in contact with the explosion from the fuel burning... it's in contact with the head, which makes the head the hottest part of the engine... unless you count the exhaust manifold/turbo... cause that part of the engine is not being cooled by oil and water...

[vstech]

Originally Posted by funola

Anything that get's hot is heat. Most the heat from the lamp you placed next to the cylinder head is lost to the atmosphere because heat rises.

MOST of the heat from the radiant lamp I placed on my exhaust manifold with the reflector facing the head went into the head... some of that heat did get lost to the atmosphere via reflective radiation of the metal surfaces...