Question about electricity?
Question by : Question about electricity?
An instant gas hot water heater is capable of raising the temperature of 2kg of water by 50K each minute.
What problem might there be in designing a instant electric water heater which is to work from the ordinary mains supply instead of gas and achieve the same rate of heating ?
Best answer:
Answer by Jac Edga
It would need a lot of current.
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Electricity conduction in water.
Rusting of metal parts in contact with water.
May cause severe short circuit in system
Leaks can damage entire circuitry.
High current is required to heat 2L of water per minute by 50K
Use induction heater.
It is capable to do that instantly.
High current would be required: for a 110v supply it would be 63A, for 230 it would be 30A. Due to the high current it would also require it’s own special connection to the mains as for example in the UK (230 v) the highest rating of plug size would is 13A which falls short of the 30A required.
There would also be the issue of running the heater, in the UK it is more economical to use gas for heating than electricity.
The size of the heating element would need to be quite large as well to be able to transfer the amount of energy required
In the UK we have electric shower heaters rated a 9.5kW on a 230Volt supply, the heater you suggest may need a 3 phase 400v supply
First work out the energy in joules required to raise 2Kg of water by 50 degrees per minute
energy = specific heat capacity x mass x temperature change
energy = 4187 x 2 x 50 = 418700 joules per minute or 6978.33 joules per second
since 1 joule/second = 1watt you need an electric heater of 6978 watts or 7kw
This is assuming almost 100% efficiency
In UK electric showers operating on 230 V AC are rated from 7.2 Kw up to around10Kw