Central Heating - what's best ?

[Lou]

Why is the physics of emmissivity voodoo?

A true black body radiates thermal energy better. More radiant energy into the room increases the heating of the room.

[Divingminxsy]

Originally Posted by Captain Calamity

Careful mate. If SWMBO reads this you risk a kick in the nuggets.

CC

His nuggets have disappeared - it's really freezin here !

[Air Guzzler]

Black as a paint cover does not radiate heat better than white, blue,even pink
Domestic radiators are technically heat emitters as the previous post with diagram shows the heating of the room is carried out be convection far more than radiation thats why when you women insist on covering them in your Bridget Joneses the room takes longer to heat up

[Lou]

Thermal paint does. That's what it is designed to do. Why on earth do you think heat sink fins are coated matt black?

Of course radiators are misnamed and should be called convectors, BUT, radiative heat has an instant effect, and is part of the bonus of a real fire, and enhancing radiative heat is only an additive effect to that gained by convection, it is not a one or the other situation.

[Air Guzzler]

Heat Transfer

Heat is given off when an object's thermal energy is transferred. Thermal energy (see below) can be transferred in three ways: by conduction, by convection, and by radiation.

1. Conduction


Conduction is the transfer of energy from one molecule to another. This transfer occurs when molecules hit against each other, similar to a game of pool where one moving ball strikes another, causing the second to move. Conduction takes place in solids, liquids, and gases, but works best in materials that have simple molecules that are located close to each other. For example, metal is a better conductor than wood or plastic.


2. Convection

Convection is the movement of heat by a liquid such as water or a gas such as air. The liquid or gas moves from one location to another, carrying heat along with it. This movement of a mass of heated water or air is called a current.

3. Radiation

Heat travels from the sun by a process called radiation. Radiation is the transfer of heat by electromagnetic waves. When infrared rays strike a material, the molecules in that material move faster. In addition to the sun, light bulbs, irons, and toasters radiate heat. When we feel heat around these items, however, we are feeling convection heat (warmed air molecules) rather than radiated heat since the heat waves strike and energize surrounding air molecules

[Lou]

The heat you feel on your face when you turn it to the sun is radiated heat. A hot black body in a room will radiate heat and warm up items in the room, qhich in turn will conduct heat to their surroundings.

Therefore there is an additive effect from radiative heat to the quantity of energy in the room from convection alone. The same applies with radiators, but a shiney white radiator has poor emmissivity. By improving the emmissivity the total heat transfer from hot water, to room air, contents and furnishings can be increased.

[fatboy]

we have a candle on the kitchen table, we all gather round it holding our hands out to it


















when the kids complain that they are still cold, i light it!




bah humbug

[Jay_Benson]

Originally Posted by Lou

Why is the physics of emmissivity voodoo?

A true black body radiates thermal energy better. More radiant energy into the room increases the heating of the room.

Lou - you seem to forget that Physics is for the devil and is very complicated.

Black bodies both collect and radiate heat better than other coloured bodies otherwise the same.

[Jay_Benson]

If I was to build a house from new then I would have a ground source heat pump heating the house using underfloor heating in addition to a woodburner. Obviously there would be loads of insulation so that the heat I have collected doesn't get out.

I am wondering whether anyone has had a look at installing "underfloor" type heating systems on the walls of a house - it may be a better retrofit solution for existing houses.

[Woz]

Originally Posted by pauldiving

i have put a log burner in and hardly put my gas central heating on now,

i bring home offcuts of timber home from work and its free heating!!

The business 3 doors down makes hardwood joinery (doors, mostly). Free hardwood for the wood burner. And I can also see Fernwood Fuels from my office window if you fancy some coal/smokeless. You have to bag it yourself but it's incredibly cheap.