Heat transfer in water heater 1

[brightonbill]

I have an interesting problem that I am struggling to solve.

I am working on a residential project in which the client would like to install a 100L water storage heater to provide hot water to a shower. The hot water heater has 2No. 6kW elements and the water flow required is 0.15 L/s to the shower. Assuming the mains cold water supply is at 10 degrees C and stored water is at 60 degrees C with a mix at the shower head of 38 degrees C how do I work out the amount of time the hot water will last at 38 deg C and what will be the steady state temperature of the hot water supply when the tank is exhausted?

Please humour me.

Bill

 

[racookpe1978]

On the other hand.

IF this room in inside a house in colder climates, then the "lost heat" from the water heater would offset the need for heating energy when the room is unoccupied. (Like leaving a light on, the lost heat from the water heater will keep the unoccupied room warmer than no heat or lights at all.)

Is that offset enough to pay for the electric power used when nobody is inside?

My summary? At 600.00 per night, your guest WILL DEMAND plenty of hot water for as long as they want to run the hot water. NO compromises will be accepted, and at 600.00 per night, word-of-mouth is fast and very damning.

 

[IRstuff]

Something like this:

http://www.rheem.com/product/point-of-use-tankless-electric-rte-27

which would provide a 50F delta at 4 gpm. You could get by with the 18kW unit, which gives you the same 50F delta at 2.6 gpm ( your requirement is 2.4 gpm)

Home Depot sells the 18 kW unit for $430:

http://www.homedepot.com/p/Rheem-Ec...kless-Electric-Water-Heater-RETE-18/202514585

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