Way off. Your element resistance is 240²/2000 = 28.8Ω.

Am I confused? That is a very small resistance value, which is used in the hair dryer?!!

 

I got a reading of about 500 ohm of this coil from my not-reliable multimeter. That is why I want a guess from you.

It seems now reasonable as the hair-dryer is powered by 240V ac with about 24V drop across the dc motor. It is quite hot in its original state.
Look like it is true that the 5V from the power bank may not get hot with this resistance value which I think may need some 500k ohm??? Or do we need to replace it with some 100k resistors connected in series as in some youtube video?

The hair dryer has a max power rating of 2000W. Let me know in case you still need other data?
The output of most power bank may be just 5V at 2A Max.

However, I did read about news how these USB LED lights get hot, when it is powered from the 5V usb ac adapter. So this may be another idea for getting heat from the 5V power bank. I try to make a hand warmer for my personal use only, when I am feeling very cold.

Below are some reference so there may be more discussions:
USB Hand Warmer Review & Teardown Pebble Hands Treasure NS-518 mobile Power Supply

Mini Pebble Hand Warm Charging Treasure Explosion-Proof Mobile Power Bank
https://handok-speaker.en.made-in-c...easure-Explosion-Proof-Mobile-Power-Bank.html

P.S. 1 - power bank capacity: 3.7V, 5000 mAh ( the size of this will not make it so heavy )

View attachment 212223

3.7 volts times 5 amp hours gives 15.5 watt hours, at whatever current the 5000 milliamp hours were calculated. So you need to consider how much heating that can provide for whatever length of time.

 

There is remaining a problem: as I tested, it seemed that the power bank did not function if connected just a resistor across it. Can someone confirm this? May be a 5V USB power adapter have to be used instead.

P.S.1

Now the idea seems to become one that, determine the value of resistor required to connect across the 5V USB power adapter (via microUSB cable), typically have following output:
5V-3A, 9V-2A, 12V-1.5A
( why there are so many voltage values? )
to heat up to about 40C in about a minute from room temperature (may be 20C).

 

There is remaining a problem: as I tested, it seemed that the power bank did not function if connected just a resistor across it. Can someone confirm this? May be a 5V USB power adapter have to be used instead.

What was the value of the resistor? How’d you know it didn’t function?

If the resistor is too small, the current drawn from the battery may be too high and may cause the battery to heat up. Either case might have tripped protection circuitry and shut the battery down.

 

Am I confused? That is a very small resistance value, which is used in the hair dryer?!!

Yes, at the maximum setting, if the dryer is truly 2000W as you said in post #28.