Author Topic: EEVblog #1187 - Room Heater Technology Explained  (Read 1608 times)

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EEVblog #1187 - Room Heater Technology Explained
« on: March 04, 2019, 10:29:33 pm »
A comprehensive tutorial on room (space) heater technology and their effectiveness and efficiency in heating rooms and homes.
The different types of heat transfer are discussed, along with the different types of heater technology available and how they apply to room and object heating. The 2nd law of thermodynamics, and the impossibility of new graphene technology in the Solus Kickstarter project.
Infrared panel heaters, Infrared IR radiation heaters, and convection heaters. The BTU and power equivalence is explained. And a demo of thermal heat through glass.

 

Offline johnlsenchak

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #1 on: March 04, 2019, 11:22:37 pm »

Sorry  Dave, no offense but this  video  didn't interest me that much 8)
« Last Edit: March 04, 2019, 11:24:35 pm by johnlsenchak »
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Offline bsfeechannel

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #2 on: March 05, 2019, 12:02:36 am »
Brilliant. Now it is very clear that their demonstration is not reliable to say the least.

They leave a thermometer on the floor in the path of radiation of their heater. The other thermometer is on the same wall as their heater where there can be conduction. Then they place a convection heater conveniently positioned so that neither radiation nor conduction can heat them. Wow!
 

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #3 on: March 05, 2019, 01:10:18 am »
If heat conducting through the ceiling is working against you, what if you used a heat pump to blow cold air at the ceiling while blowing warm air in a more useful direction? (Let's assume using a heat pump to take heat from the outdoors is not an option for whatever reason.) Then the ceiling would be cooler so less heat lost.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

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Offline Razor512

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #4 on: March 05, 2019, 01:26:12 am »
Couldn't the heater be less than 100% efficient if the losses are happening outside of the location you want heated?

For example, my home uses an ancient furnace and steam based heating system where the furnace boils water and the steam then flows to the radiators in the rooms of the home.
i is a gas based system so it is harder to calculate the energy input, but I have legitimately been able to reduce my heating costs by using fans to force the cooler air in the room through the radiator.

Forcing the air through, heats each of the rooms faster, though it has no impact of the fuel usage of the furnace beyond a the steam pressure gauge reading a little lower, but with the air being forced through, the furnace spends less time on, and it has actually lead to lower fuel costs.

While the natural gas is being converted to heat, not all of it makes it to the rooms while that flame is running at full blast.
 example of the ancient heaters.

 

Offline helius

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #5 on: March 05, 2019, 02:31:07 am »
For example, my home uses an ancient furnace and steam based heating system where the furnace boils water and the steam then flows to the radiators in the rooms of the home.
Energy efficiency is a concept that describes how much energy is used, vs. how much does useful work that we want. Wuseful / Wused is one way of writing it. You must be careful, because different sources of energy behave in very different ways.

The video is about electrical resistance heaters. They work by connecting a resistor across the line, so that the power drawn from the utility (V * I) is dissipated in the resistor (V2 / R). In practice some voltage is dropped by the supply wiring and the power cord, so they are not quite 100% power efficient, but close enough. Any appliance that runs from mains electricity will have those losses.

When using combustion for heating, the system is absolutely not 100% efficient, because heat energy is contained in the exhaust gases. If those gases are vented straight up a chimney, they carry away roughly 20-30% of the heat energy released by combustion, leaving 70-80% to actually heat the building. More recently, condensing heat recovery devices have become more common, which reduce the heat losses to between 3-10%. If you see a building with "smoke" pouring out at ground level, that is what is happening. The "smoke" is in fact water droplets or mist that have condensed from the hot exhaust as it exchanges most of its heat with the cold intake air.

However, this efficiency comparison can be misleading, because hydrocarbon fuels and electrical power are not the same. The electrical power has usually to be generated at a remote plant, transmitted over a long distance, and converted several times, which represents a built-in loss of energy that cannot be measured at the point of use. Fuels require energy to refine and transport, which is also not measurable at the point of use. If the electrical power is generated from fossil fuels, it is lower in all-inputs efficiency than even 70%-efficient combustion furnaces.

It is also possible to achieve greater than 100% energy efficiency by using heat pumps, since part of the useful work is being extracted from the environment.
 

Online blueskull

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #6 on: March 05, 2019, 02:40:04 am »
"500 Internal Server Error" doesn't heat my room.
 

Offline helius

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #7 on: March 05, 2019, 02:47:08 am »
Forcing the air through, heats each of the rooms faster, though it has no impact of the fuel usage of the furnace beyond a the steam pressure gauge reading a little lower, but with the air being forced through, the furnace spends less time on, and it has actually lead to lower fuel costs.

In your case, there is a thermostat in the living space that actually controls how long the furnace stays on. The radiators themselves do not sense the temperature. So there is a laggy control loop between the radiators heating and the thermostat registering that sufficient heat has been produced. By blowing fans you have in effect lowered the thermal impedance of this loop: so the radiators overshoot less. Whether this makes the space more comfortable depends largely on whether you spend time closer to the radiators or closer to the thermostat.
 

Offline Razor512

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #8 on: March 05, 2019, 07:00:57 pm »
For me, it makes the place more comfortable. The thermostat is located at a central point in the home (Honeywell Lyric Round), though the furnace has a number of its own safety features that work to keep certain failures from happening, though I assume there are possibly some losses due to the locations of the radiators, for some reason older homes using these types of heating systems, always place the radiator under a window with a portion of the unit recessed in the wall. When the housing in the area was built they used furnaces rated for twice the square footage of the homes they built, and then they just added additional pressure gauges and different exhaust vents that open when needed.

Overall, it is just weird how it ends up bringing the entire room to a comfortable temperature more quickly when some active airflow through the radiator.

All of the radiators are this style
where a fin stack is used instead of a few loops of pipe, and augmenting them with fans to force air through them, actually cut my heating bill, though the system is still more expensive to operate than a modern central heating system that is also running on natural gas.
 

Offline drussell

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #9 on: March 05, 2019, 09:05:27 pm »
Couldn't the heater be less than 100% efficient if the losses are happening outside of the location you want heated?

For example, my home uses an ancient furnace and steam based heating system where the furnace boils water and the steam then flows to the radiators in the rooms of the home.

We are talking about electric, in-room space heaters here.  All the input electrical energy goes into heat in the room.

This has nothing to do with anything gas-fired or whole-home, multi-room set-ups.  At the very least, any gas fired system will lose some of the input energy BTUs out the exhaust, even with modern multi-heat-exchanger set-ups, which will never make it to the room to be heated, no matter what the system.
 

Offline drussell

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #10 on: March 05, 2019, 09:12:11 pm »
It is also possible to achieve greater than 100% energy efficiency by using heat pumps, since part of the useful work is being extracted from the environment.

Indeed.

Even a standard small window-mount-style air conditioner pumps about 3 times as much heat from the "cold side" to the "hot side" of the heat pump apparatus as could be dumped onto the hot side by simple resistance heating.

i.e.  A "5000 BTU" air conditioner can pump 5000 BTU worth of heat (about 1500 watts) from one side to the other using only about 500 watts of power to do the pumping.
 

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #11 on: March 05, 2019, 10:43:35 pm »
Sorry  Dave, no offense but this  video  didn't interest me that much 8)

Wow, alert the media!  ::)
 

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #12 on: March 05, 2019, 10:44:19 pm »
Couldn't the heater be less than 100% efficient if the losses are happening outside of the location you want heated?

Sure, but that's not what's being discussed in these videos.
 

Offline lpaseen

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #13 on: March 05, 2019, 11:59:44 pm »
So, around 12:48 you state that the IR radiation shoot straight out of the window since most glas is transparant to IR depending on wave length. Directly after you prove with your thermal camera that body heat/IR doesn't go through glass.
That makes me wonder what wavelength does a radiator actually produce, in most cases will it go through the glass or just heat the glass and then start to conduct the heat back in to the room?
 

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #14 on: March 06, 2019, 01:00:49 am »
So, around 12:48 you state that the IR radiation shoot straight out of the window since most glas is transparant to IR depending on wave length. Directly after you prove with your thermal camera that body heat/IR doesn't go through glass.
That makes me wonder what wavelength does a radiator actually produce, in most cases will it go through the glass or just heat the glass and then start to conduct the heat back in to the room?

https://www.flir.com/products/lepton/
https://www.flir.ca/discover/what-is-infrared/
"Spectral range: Longwave infrared, 8 µm to 14 µm"

https://en.wikipedia.org/wiki/Infrared_heater
"Tubular infrared lamps in quartz bulbs produce infrared radiation in wavelengths of 1.5–8 µm." "Ceramic infrared heat systems useful wavelength range is 2–10 µm."

https://rayotek.com/tech-specs/material-comparisons.htm
Soda-lime transmits from about 0.3µm to 2µm

So you will get some infrared passing through, but nothing that the FLIR can see.
 
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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #15 on: March 06, 2019, 03:40:48 am »
So, around 12:48 you state that the IR radiation shoot straight out of the window since most glas is transparant to IR depending on wave length. Directly after you prove with your thermal camera that body heat/IR doesn't go through glass.
That makes me wonder what wavelength does a radiator actually produce, in most cases will it go through the glass or just heat the glass and then start to conduct the heat back in to the room?

In the case of the Solus and other "IR Radiators" that uses glass panels, they would obviously pick a wavelength that goes through the glass. They are sold as IR panels and I have little doubt the glass is IR transparent. Of course as stated, it's never 100% IR.
 
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Offline AutogolazzoJr

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #16 on: March 08, 2019, 02:22:27 am »
I bet you guys have all heard the news: kickstarter decided to take action and suspend funding on the heater. I assume that it will be back, but without all of the efficiency nonsense. They will probably still be bragging about the "wooh wooh graphene".
 

Offline Poe

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Re: EEVblog #1187 - Room Heater Technology Explained
« Reply #17 on: March 08, 2019, 07:59:43 pm »
This Kickstarter, like many, just implies too much and explains too little.  If they solved the oxidation issue like they claim, it's honestly an improvement over existing space heaters though.

Read the claims with the following in mind and they become less 'scammy' and more interesting..

"Save over 80% on your next heating utility bill."
Their energy savings claims are based on comparing radiated heaters to conduction heaters, not traditional quartz radiated heaters to their new wizbang graphene heaters.  They make a point to clarify this "compared with conventional water based radiators". 
Although I agree that this is misleading because people will assume it will heat their entire room, people do in-fact save when using radiated heaters because they don't have to heat their entire room.  Many uninsulated cabins in the States are heated with radiant heaters because heating the air first consumes way more energy.  They tend to use gas because electric quartz elements don't last very long. 

"The Most Efficient Radiator In The World"
A conventional quartz IR element will generate the most radiated power when new.  As it ages, less is radiated and more is conducted.  This graphene element (if it doesnt' oxidize) would generate the most radiated energy for the amount of energy used.

At 27:40 you mention that a heater placed near heat losses will make it harder to heat the other side of the room.  Although correct, this placement is the recommended way to install a heater.  Placing it on the other side of the room causes us fleshbags to request more BTUs for the same comfort level.   That comfort is an important point because it determines the BTU demand since we're part of the control loop.

I completely understand what you're saying about all electric heaters being 100% efficient, but I've designed HVAC control systems for companies and can tell you that wattage is not the only thing that determines BTU demand.  Things like humidity, temp gradients, surface temps, etc can offset the BTU requirement by a massive amount.... thanks to us fleshbags controlling the knob.  It can't be ignored.

For example, compare a 1000W soldering iron vs. a well-designed convection system circulating 500W of high volume turbulent air into the middle of the room with another 400W of IR shining down on a wood floor... with a 100W humidifier.  The latter will have slightly more losses due to airflow over the walls, but it will have massively better gradients and humans would reduce the BTU demand to <500W for the same feel.

It might be dishonest for someone to say the second system is more efficient than the soldering iron, but I think it would be acceptable to say it reduces energy consumption.  Caveat emptor

Not sure what it's like down under, but in the states, most windows reflect rather than absorb the majority of IR light due to internal gasses and coatings.  Our EnergyStar programs have required an ever-increasing reflection percentage for the past few decades.  This Kickstarter heater most likely has similar reflective coatings on the backside to presumably increase radiated power out the front.

At the end of the day though, invest in good windows and a heat pump.  So glad I invested in mine.  Has an ROI better than anything else you could do with your house.  Including solar.
 


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