Heat from a 15W lamp?

[ericmark]

I want to increase my brewing output. At the moment I use fridge section of a fridge/freezer the motor is never used, just a 18W demo heating tile. It works well 40 pints every three weeks. But in summer I have to stop as heat controller with either heat or cool not both at the same time.

So second controller this time a STC 1000 that will heat and cool giving the option of summer brewing, but also double winter output.

Now the freezer compartment is smaller then the fridge plus it has a step where the motor is bottom draw was not as deep as the rest. So no flat bottom so Meccano will have to come out to fill the space, and in that space I will need a heater of some type.

Looked at reptile heating mats 11" x 11" at 12W seems about right, but it states “These heat mats use Ultra Long Wavelength Infrared emitted from the printed carbon.” So not so sure if the heat will transfer OK into the plastic fermentor. Other option is a simple bulb, but how much of the power put into a bulb is turned into heat?

Would 2 x 30W in series be better than a 15W? If it gives off light does that mean a reduction in heat. Is the heat infrared from a simple bulb if so will it heat the fermentor as well as an other type. I have considered all sorts including an aquarium heater in the old bottom draw filled with water.

Do not want to go too large with heater as over shoot is a problem. Even with 18W sensing the side of fermentor insulated with a car cleaning sponge I can get a 2~3°C over shoot if start temperature is 2°C low to start with.

Sent for STC 1000, but rest in design stage so ideas on heating. I will guess less heat loss from freezer than fridge, and 18W is too big for fridge may only need 10W so any ideas?

 

[JohnD]

how much of the power put into a bulb is turned into heat?

Pretty well all of it. A 15W bulb gives off almost exactly 0.015kW of heat. if it is in a closed and insulated container you won't be able to measure the difference.

Sadly I don't recall the calculation or measurement, but I do recall the principle from some physics class long ago, and IIRC the visible light turns into heat when it hits something and is absorbed.

You might consider a large and a small lamp, turning off the large one before target temperature is reached.

 

[JohnW2]

Other option is a simple bulb, but how much of the power put into a bulb is turned into heat? ... Would 2 x 30W in series be better than a 15W? If it gives off light does that mean a reduction in heat.

I agree with JohnD. If a bulb/lamp consumes 15W of electricity, then that must be turned into a total of 15W of (heat + light). If the enclosure doesn't let any light out, all that light must also get turned into heat (what else could happen to it?) - so you will end up with a total 15W of heat.

Is the heat infrared from a simple bulb if so will it heat the fermentor as well as an other type.

I don't really understand the question - infrared is 'heat'.

Kind Regards, John

 

[EFLImpudence]

It could be Schrodinger's light.

 

[bernardgreen]

I don't really understand the question - infrared is 'heat'.

Infrared is electromagnetic radiation. It is energy and not heat. It heats any material that can absorb it by agitating the molecules of that material with the energy in the infra red radiation. It can be reflected by materials which do not absorb that spectrum of electromagnetic radiation.

 

[ericmark]

OK question answers as far as heat goes, I want the heater to be required 90% of the time when garage is at 5°C which should stop any over shoot or at least keep it within a couple of degrees.

Infrared is more of a problem as I don't know what it will pass through and what it will heat? Fermentor is thermal plastic and beer mainly water, I know infrared passes through air but what does it do with water? Main problem as with all infrared heating is will the sensor read the correct heat?

I would guess it would heat water, but only a guess.

The cooling side is a huge problem. A standard fridge removes too much energy per time unit, so air is quickly cooled to 4°C (when fridge's own temperature control stops motor), but it can take some hours before the brew even drops to 18°C. I have worked out lowest air temperature required is 16°C, but as yet have not got the instructions for the STC 1000 controller so difference which can be set between heating and cooling is unknown.

More expensive units will gradually alter the mark/space ratio as the temperature approaches the set temperature, but my basic system simply turns the heater or refrigeration unit on and off at the set temperature. Heating should be easy just select the smallest heater that will do the job. Cooling is more of a problem as simply the fridge/freezer motor is far too big.

However if beer gets too cold it just stalls no damage done. Only too hot messes it up. So hope is fridge/freezer will only run when we get an unexpected warm spell in the summer months which is rare. Most of the time all control will be with heater only.

 

[JohnW2]

I don't really understand the question - infrared is 'heat'.

Infrared is electromagnetic radiation. It is energy and not heat. It heats any material that can absorb it by agitating the molecules of that material with the energy in the infra red radiation. It can be reflected by materials which do not absorb that spectrum of electromagnetic radiation.

All true, but, AIUI, it is the part of the EM spectrum most readily absorbed (hence converted into heat) by many/most materials, which is why it is generally (I suppose 'colloquially') regarded as 'heat'.

Kind Regards, John

 

[JohnW2]

Infrared is more of a problem as I don't know what it will pass through and what it will heat? Fermentor is thermal plastic and beer mainly water, I know infrared passes through air but what does it do with water? Main problem as with all infrared heating is will the sensor read the correct heat? I would guess it would heat water, but only a guess.

I may be a bit out of my depth here, but I think it depends crucially on what you mean by "infrared". In your OP you mentioned "Ultra Long Wavelength Infrared". That presumably refers to 'far infrared', which is verging on 'microwave' and, AIUI, interacts with molecules of materials in a different way from the more common near-infrared (and to some extent mid-infrared) radiation (such as, for example, one would mainly get from traditional 'radiant' hob elements, infrared lamps and old fashioned X-bar electric fires).

I may be wrong, but I don't think that near infra-red (and probably also mid-infrared) will significantly 'pass through' many solid materials, and doesn't necessarily even pass well through liquids or gases - even materials which are very 'transparent' to visible light are often not very 'transparent' to IR (e.g. glass, or even collections of 'greenhouse gases') - hence 'the greenhouse effect' (whether in a greenhouse, the atmosphere or wherever). It will be absorbed at the surface of a material, creating heat, but I think that onward propagation of that heat will then be primarily by conduction and convection - much as with water in a saucepan or (non-electric!) kettle being heated by a 'radiant' hob element. I would imagine that is what would happen with you fermenter.

Someone who knows what they are talking about may be able to give you some more useful answers!

Kind Regards, John

 

[TheVictorian]

Why not use a tubular greenhouse heater like the rest of the brewing community? Myself included.

 

[JohnW2]

Why not use a tubular greenhouse heater like the rest of the brewing community? Myself included.

I wondered that, but eric seems to think/know that he needs far less heating power than such devices usually provide.

Kind Regards, John

 

[ericmark]

You are correct the tubular heater 28W is the smallest I have found which would cause a massive over shoot. The heater I am using in the fridge is 18W and too big really.

Fridge size 288 litres, A+ it needs 185 kWh/annum to keep it at 5°C when kept in a room of 32°C which is far more temperature differential than I will get, taking that as an example. So 21.5W will keep a 27°C differential. I need around 15°C differential so need around 12W. Yes a fridge unit works better than a heater, but it's logarithmic and I have taken it without applying that so they will cancel themselves out. Also if I don't maintain the temperature no harm will be done it will just take longer.

12W also seems to line up with experience over the last year. The freezer is smaller than fridge so more like 10W. Using a heater 3 times larger than required is going to cause over shoot.

 

[stillp]

What about wrapping the glass envelope of the lamp in aluminium foil? Then none of the light could escape, so all the 15W of input energy would appear as heat. However, I'm sure that the amount of energy that 'escapes' a lamp, and is not dissipated as heat in the lamp, is a smaller proportion of the lamp rating than the manufacturing tolerance. ISTR that automotive lamps have a tolerance of +50-25%.

 

[JohnW2]

What about wrapping the glass envelope of the lamp in aluminium foil? Then none of the light could escape, so all the 15W of input energy would appear as heat.

I suspect the lamp might well 'overheat' and suffer as a consequence - since heat, as well as light, 'escape' would be impaired. However, perhaps I misunderstood, but I thought this lamp was going to be within an 'enclosure' from which light could not escape. If that is the case, then all of the electrical energy will end up as heat within the enclosure, even without the foil.

Kind Regards, John

 

[ericmark]

What is likely the best option are the little heaters found inside electric panels. However google panel heater and I get something completely different.

these look great but at £18.84 seem a bit on the expensive side.

 

[bernardgreen]

They are called anti condensation heaters

http://www.heattracing.co.uk/blog/a...ion-heaters-for-cabinets-and-small-enclosures