# Efficient way to convert kinetic energy to heat

#### kevin_tee

I am trying to find the most efficient way to convert kinetic energy to heat. The first thing I know is friction, however friction cause wearing for long term use. The second is convert to electric energy(dynamo) and then convert to heat using electric coil, however I think that has low efficiency and cost way more. Any ideas?

Thanks

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#### russ_watters

Mentor
Essentially every method of converting kinetic energy to heat is 100% efficient because heat is the product of all forms of inefficiency!

#### kevin_tee

Yes, I understand that every form of energy will be convert to heat eventually, I am asking are there commercial machine that convert kinetic energy to heat?

#### Nidum

Gold Member
There are machines which are designed to provide a predictable and measurable load on equipment under test .

These machines are generally called dynamometers .

Many varieties but one common design for higher powers uses paddles rotating in water . The drag of the paddles in the water provides the load and all of the incoming energy is converted into heat .

There are types with simple radial paddles and more complex ones with arrangements of rotors and stators designed using rotodynamic pump principles .

Look up : Hydraulic Dynamometer .

#### kevin_tee

There are machines which are designed to provide a predictable and measurable load on equipment under test .

These machines are generally called dynamometers .

Many varieties but one common design for higher powers uses paddles rotating in water . The drag of the paddles in the water provides the load and all of the incoming energy is converted into heat .

There are types with simple radial paddles and more complex ones with arrangements of rotors and stators designed using rotodynamic pump principles .

Look up : Hydraulic Dynamometer .
Wow, thanks I was looking at Joule's heat apparatus, but I didn't know this one.

#### russ_watters

Mentor
Yes, I understand that every form of energy will be convert to heat eventually, I am asking are there commercial machine that convert kinetic energy to heat?
Perhaps @Nidum gave you all you needed, but if not, I'm still finding this too broad/vague: do you have a specific requirement, a specific source and amount of kinetic energy and specific need to convert it to heat? Because the general answer is still that essentially all commercial machines do that.

For example, though, if you have something spinning that you want to stop. But it sounds like you WANT the heat, which is a bit unusual.

#### Baluncore

In what form will the KE be delivered? Is it a rotating flywheel or a mass moving in a straight line? Is the mass solid or liquid?
It would also help if you knew how much KE needed to be converted over what period of time. That will define the power and cost of the energy converter.

#### rbelli1

Gold Member
low efficiency
Depending on the generator size you can get high 90% efficiency. Also if your goal is heat then the energy lost to inefficiency heats the generator. Just put the generator at the location you wish to heat. Like russ said. You get an efficiency indistinguishable from 100%.

BoB

#### rbelli1

Gold Member
I cannot say much about the over unity
I can. It didn't happen.

If your process can extract heat from the environment then you get some "bonus energy" out that you personally did not supply. A heat pump is only ""over unity"" in the same way as a car is ""over unity"". I only pressed lightly on the pedal and went 0-60 in 5 seconds!

BoB

#### NascentOxygen

Mentor
The second is convert to electric energy(dynamo) and then convert to heat using electric coil,
If your K.E. can take the form of rotational motion then you could move horse-shoe magnets furiously over a steel or brass plate to cause eddy current heating/losses within the steel. Polished surfaces and a teflon coating should see mechanical wear minimised to give the setup longevity.

Might find some eddy current videos on youtube.

#### Nidum

Gold Member
There is or was somewhere a district heating system which generated heat directly from a natural source of falling water .

The energy in a large flow of water was used to heat a smaller flow of water for the heating system .

I can't find any reference now . Best guess is that it used a turbine and a water churning device like the dynamometer mentioned in #4 .

#### Hiarum

A pony brake is a good start!

#### Baluncore

"Efficient way to convert kinetic energy to heat"

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