Difference between duct fan and propellor?

[TT-01 Mamba]

What is the difference between an electric duct fan and a propellor?
i know the duct fan has a "case" around it but is one more effecient?

[Vince]

Ducted Fans move a little bit of air quickly. This always involves greater losses than moving a lot of air slowly. So a ducted fan typically takes more power to fly than the same plane with a larger diameter prop.

[TT-01 Mamba]

so why do people bother with them?
is it so that small planes will go faster?

[Vince]

Oh, I guess I did leave out the advantages of DF over props.

DF looks cool. You can put them into cool airframes and have scale looking jets.
DF does move air faster, so they have a higher theoretical top end.

[TT-01 Mamba]

but in reality a fan is more powerful
i need power more than speed
im going to attack two fans on my car to help my mamba system

[Vince]

I am not sure that I would say a fan is more powerful.
The power available is controlled by the volts of the battery and the current draw of the motor. These are the same regardless of a full prop or a Ducted Fan (DF).
A prop will produce more thrust. As the airspeed approaches the speed of the air moved by the prop, thrust will approach zero. Since a DF moves air faster, it will produce thrust at a higher air speed than a prop will.
Attach then to a car? For propulsion? Or internally, to cool down the hot components?

[Mark R]

They have fans I believe for cooling car esc's on the market have you looked into those?

[Vince]

Ah, cooling fans. You are talking about a different system that I am familiar with. I was thinking of DF for flying.

[TT-01 Mamba]

i've got some cooling fans already but i want to attack a couple of fans to the sides of my car to give a bit extra speed
the car travels about 50mph now but the motor is under alot of stress and heats up quickly