Cooking Oil dumped in GU Paddington.

[peterboat]

6 minutes ago, IanD said:

 

It's not just the temperature -- as you say, radiation increases *very* rapidly with temperature, which is why domestic "radiators" dissipate something like 90% of their heat by convection.

 

It's to do with infrared emissivity (same as absorption in reverse) -- for visual light and near infra-red (short wavelengths) which is what the sun puts out, colour makes a big difference, hence the white vs. black difference on sunny balance beams. But for the far infra-red which is what low-temperature bodies like radiators emit, colour makes little difference, all painted surfaces have very similar (and high) emissivity. What is *really* bad is polished metal...

 

https://www.thermoworks.com/emissivity-table/

 

Most common materials (including paint of all colours, wood, brick, concrete, fabric, ice, plaster, rubber, soil, tile, water...) are in the range 0.84-0.97, meaning they only radiate between 3% and 16% less than an ideal black body -- the differences between them are small, especially when only a small fraction of the total heat is radiated anyway (e.g. "radiators"). This is why there's only a *very* small difference in heating performance between black and white radiators (see earlier link which quoted 1%) -- and measurements back this up, it's not just some arcane physics theory with no relevance to the real world... 😉

 

Polished metal however is *really* bad at radiating/absorbing infrared (polished brass is 0.03, copper 0.05, chrome 0.1) so this is the worst possible finish for radiators -- even if it's trendy... 😞

Every day is a learning day, didn't know about crime finish being bad on radiators 

On 28/02/2024 at 22:36, matty40s said:

Cooking oil has been illegally dumped in the GU over a 6 mile stretch West of Paddington. Source is yet unknown, but it is costing CRT £10k a day to continue the clean up operation.

See BBC London.

This has been on London boaters Facebook page since the weekend  CRT put up oil control booms but allegedly no signs, London boaters broke through the booms!!!  That claimed they wouldn't have worked anyway!! I commented they would have worked better than a broken boom. They have also been complaining about no cleanup for birds, charities have been doing it. Also EA are supposed have taken over the operation but say the veg oils will biodegrade I think that means they arnt doing anything? Big thread on there about it

[magnetman]

16 minutes ago, IanD said:

 

This is why there's only a *very* small difference in heating performance between black and white radiators (see earlier link which quoted 1%) -- and measurements back this up, it's not just some arcane physics theory with no relevance to the real world... 

 

 

The question in the physics test was 'which is more efficient a black or a white radiator?'.  It isn't asking about percentages. The teacher said it was white probably because they had white radiators in their house. The teacher was also a non reflecting furriner so they may have had pre-installed value systems around black and white. 

 

Dictionary

Definitions from Oxford Languages · Learn more

 

 

 

 

 

more

determiner

1. a greater or additional amount or degree of.

   "she poured herself more coffee"

 

9 minutes ago, peterboat said:

Every day is a learning day, didn't know about crime finish being bad on radiators 

 

Is a crime finish all the blood after the radiator has been used to bludgeon an gangland opponent?

Edited March 1 by magnetman

[IanD]

7 minutes ago, magnetman said:

The question in the physics test was 'which is more efficient a black or a white radiator?'.  It isn't asking about percentages. The teacher said it was white probably because they had white radiators in their house. 

 

Dictionary

Definitions from Oxford Languages · Learn more

 

 

 

 

 

more

determiner

1. a greater or additional amount or degree of.

   "she poured herself more coffee"

 

As I said, in physics terms you were right to the question as asked, but in real terms the difference is negligible.

 

Since they didn't specify the precise paint finish and matt white paint has higher emissivity than gloss black paint, the opposite can also be true, and you could have been wrong... 😉

Edited March 1 by IanD

[Ronaldo47]

At college, one professor was fond of posing occasional  questions in tutorial exercises that could not be answered because insufficient information had been provided.  

Edited March 1 by Ronaldo47
typos

[magnetman]

I reckon because almost all radiators are white people are generally conditioned to assume that is the best colour. 

 

in terms of fitting in with ordinary decor and encouraging light into what may otherwise be dark areas it probably is the best colour. 

 

 

One wonders how efficient a rusty radiator would be. 

 

Maybe the painting thereof is a red herring and just done so paint companies can make more profit. 

 

 

 

The Great Paint Scam. Look out !

[Machpoint005]

There's confusion between a household "radiator" and a radiator in a physics sense. The latter is a surface that radiates heat, not a specific device.

 

 

 

[IanD]

5 minutes ago, Machpoint005 said:

There's confusion between a household "radiator" and a radiator in a physics sense. The latter is a surface that radiates heat, not a specific device.

 

 

No confusion that I can see, the same laws apply to both... 😉

 

24 minutes ago, Ronaldo47 said:

At college, one professor was fond of posing occasional  questions in tutorial exercises that could not be answered because insufficient information had been provided.  

 

As an example of practical vs. theoretical disconnect, I seem to remember a question about the terminal velocity of a cow thrown out of a high-flying aeroplane where the answer began "Assuming a cow is smooth and spherical..."

[magnetman]

Was there a word missing. It may have been a cow pat. 

This would also be a considerably more straightforward article to coax into a plane than its producer. 

[David Mack]

1 hour ago, IanD said:

Polished metal however is *really* bad at radiating/absorbing infrared (polished brass is 0.03, copper 0.05, chrome 0.1) so this is the worst possible finish for radiators -- even if it's trendy... 😞

But since household radiators produce little of their heat output by radiation it doesn't make a lot of difference if they are polished.

[ditchcrawler]

1 hour ago, IanD said:

 

No confusion that I can see, the same laws apply to both... 😉

 

 

Just because they are called radiators doesn't mean they are radiators, look how many people call vacuum cleaners Hovers when they are Electroluxs or Dysons

[BEngo]

16 minutes ago, ditchcrawler said:

Just because they are called radiators doesn't mean they are radiators, look how many people call vacuum cleaners Hovers when they are Electroluxs or Dysons

And then there was the hover Hoover aka the Constellation.   Looked a bit like a flying saucer IIRC.

 

N

Edited March 1 by BEngo

[Jen-in-Wellies]

On 29/02/2024 at 14:03, David Mack said:

I was thinking of that too. The teacher told us that if there were no constraints the oil would spread out until the layer was one molecule thick. By estimating the drop size and then measuring the extent of the 'slick' we could calculate the size of an oil molecule.

If I recall, it was a long time ago, the pretty* colours were related to an interference effect on light, which was related to the oil film thickness.

 

* Not so pretty, if you are an aquatic bird, with oil in your feathers.

[MtB]

2 hours ago, magnetman said:

I reckon because almost all radiators are white people are generally conditioned to assume that is the best colour.

 

No. Back in the late 70s when I was slinging in new heating systems in (mostly) Victorian terraces, radiators were almost universally supplied in a very pale grey primer, on the assumption that people would paint them the colour they wanted. Everyone painted them white.

 

Eventually one manu noticed and started supplying them in proper gloss white and even though this made them more expensive, they cornered the market for a while.

 

Eventually all the other manus realised why their sales were dropping and swapped to gloss white too. 

 

[IanD]

1 hour ago, David Mack said:

But since household radiators produce little of their heat output by radiation it doesn't make a lot of difference if they are polished.

There's an echo in here... 😉

[Ronaldo47]

5 hours ago, IanD said:

As an example of practical vs. theoretical disconnect, I seem to remember a question about the terminal velocity of a cow thrown out of a high-flying aeroplane where the answer began "Assuming a cow is smooth and spherical..."

A couple of decades ago, wasn't there a story in the  papers about an incident in, I think, India, where a cow that was being transported by air, broke loose,  fell out of the plane, and hit and sunk a boat? I remember it coming up in an episode of, I think, "The News Quiz"  or "Have I got News for You",  where one of the panel was the formidable wife of the "Cash for Questions" MP whose name I forget. 

Edited March 1 by Ronaldo47
typos

[Mike Todd]

6 hours ago, IanD said:

 

No confusion that I can see, the same laws apply to both... 😉

 

 

As an example of practical vs. theoretical disconnect, I seem to remember a question about the terminal velocity of a cow thrown out of a high-flying aeroplane where the answer began "Assuming a cow is smooth and spherical..."

Of course that statement is true, but only in the sense that 'laws of physics' apply universally, there is no class distinction. However, they impact differently depending on the circumstances. AFAIK, most heat in domestic 'radiators' is dispersed around a room by convection. (I don't know about the very small distance from the surface of the radiator and the room air - is guess that is conduction).

 

The nearest to radiation heating that I know is that favoured a few decades back for the space heating of churches - ie high level electric bars designed to maximise the amount of the energy emitted as radiation. The idea was that they only heated where it was needed rathe than the enormous cavern that comprises most traditional church/chapel buildings. The problem has been that they are indeed very focussed and you only have to move a few inches sideways to go from toast to iced tea. In addition they do not create in human bodies a feeling of being warm and, as a result, feel unsatisfactory. But they are cheap (ie less expensive) to install and to run, so long as you ignore cost/benefit!

[ditchcrawler]

13 minutes ago, Mike Todd said:

The nearest to radiation heating that I know is that favoured a few decades back for the space heating of churches - ie high level electric bars designed to maximise the amount of the energy emitted as radiation. The idea was that they only heated where it was needed rathe than the enormous cavern that comprises most traditional church/chapel buildings. The problem has been that they are indeed very focussed and you only have to move a few inches sideways to go from toast to iced tea. In addition they do not create in human bodies a feeling of being warm and, as a result, feel unsatisfactory. But they are cheap (ie less expensive) to install and to run, so long as you ignore cost/benefit!

I use to install them, the church authorities insisted they went so high in the air we called them faith heaters. I think infrared heating is coming back in fashion a bit. heat the people not the house 

[TheBiscuits]

10 hours ago, Arthur Marshall said:

Although, with St Pat's night coming up, of course, it's worth noting that the writer of Danny Boy was quite aware of plumbing's powers of communication.

 

 

Very good.

[MtB]

1 hour ago, Mike Todd said:

but only in the sense that 'laws of physics' apply universally,

 

Point of Order M'Lud,

 

The classical 'Laws of Physics' only universally apply on the macro-world side of the Heisenberg Cut, according to a programme on the R4 yesterday.

 

 

 

 

 

[system 4-50]

We've been here before.  Radiators transfer heat only by conduction and radiation.  That the air heated by these two processes does indeed move heat away in a process called convection is true, but the initial transfer of heat has to be done by conduction and/or radiation.

[Ronaldo47]

6 hours ago, Ronaldo47 said:

A couple of decades ago, wasn't there a story in the  papers about an incident in, I think, India, where a cow that was being transported by air, broke loose,  fell out of the plane, and hit and sunk a boat? I remember it coming up in an episode of, I think, "The News Quiz"  or "Have I got News for You",  where one of the panel was the formidable wife of the "Cash for Questions" MP whose name I forget. 

Google found this: a Japanese fishing boat sunk by a cow that had been stolen by some Russians,  and had got free and fallen from the military transport aircraft it was being carried in. 

https://www.rulesmaster.com/news/view/11

 

[Mike Todd]

13 hours ago, MtB said:

 

Point of Order M'Lud,

 

The classical 'Laws of Physics' only universally apply on the macro-world side of the Heisenberg Cut, according to a programme on the R4 yesterday.

 

 

 

 

 

I only used the very generic Laws of Physics not the so called Classical laws, which almost by definition , are an imperfect description  - as indeed are all if them. It is a common philosophical error to assert that any Law controls behaviour. Any scientific law is a distillation  of observations, they simply describe how things behave.

[MtB]

15 minutes ago, Mike Todd said:

I only used the very generic Laws of Physics not the so called Classical laws, which almost by definition , are an imperfect description  - as indeed are all if them. It is a common philosophical error to assert that any Law controls behaviour. Any scientific law is a distillation  of observations, they simply describe how things behave.

 

All true, but the point I was making is there are no "Universal" physics laws describing the behaviour of matter. Once you go sub-atomic, a different set of descriptions apply!

 

Its a curiosity though, that "law" as in "law of physics" describes what actually happens, while "law" as in act of parliament only describes what they would like to happen.