outside tap, winter protection

[rtbcomp]

........ using a bucket of hot water is not efficient at all because you will need more energy to heat the water in the first place......

Not necessarily, the water has to be above freezing point, you can just leave it outside if the temp is > 0 degC.

In talking about heat, we can have a high temp and low mass or a greater mass at a lower temp for the same amount of heat.

Also if we are freezing the water we are removing its latent heat of fusion.

 

[nickk]

i assume this is the principle of heating a building using ground sources,quite popular now.

 

[rtbcomp]

Yes

 

[tigler]

You could always put some buckets of water in it and freeze them down overnight.

A 100w freezer should produce about 300w of heat.

Er, sorry but no. Law of conservation of energy states that it's impossible to get more out than is put in.

 

[rtbcomp]

Please read the whole thread. We are moving energy from one place to another, not creating it.

 

[tigler]

I did, it makes no difference though.

 

[J_K]

To the OP.
Yes leave your tap open.
I sell and install irrigation systems to garden centres and plant nurseries and come across alot of frost broken taps.
They say we drained the system down but the taps still went.
That little bit of water thats sat in there has a tremendous force as it expands when it freezes.
I've seen 2" SS ball valves with a hole in the side you can put your finger in.

 

[tigler]

Yup, this is true, nothing will stop ice from expanding, it will fracture anything, witness a car engine block without anti-freeze.

 

[rtbcomp]

I did, it makes no difference though.

OK.

You are right in saying that heat can't be created or destroyed, I've never disputed that.

So, our bucket of water has mass and is at a temperature above absolute zero therefore it contains heat. Heat = mass x temp x constant

If we reduce its temperature and keep its mass the same we have removed some of the heat.

This heat cannot be destroyed, so it must go somewhere.

It goes to the coils on the back of the fridge.

It doesn't get there by itself, the fridge motor and all its gubbins pumps it. To do this requires some energy, but the energy required is less than the actual heat pumped.

So we get more heat out of the back of the fridge than the electrical energy consumed.

This heat is the sum of the electrical energy and the loss of heat from the bucket of water.

Thus no heat is created or destroyed and no laws of thermodynamics violated.

 

[tigler]

Doesn't work.
The refridgerant compressor has to work longer to transfer the heat from the water which is dissipated in the heat exchanger. So that extra work is electrical energy over time and the inefficiency in friction and heat dissipation of the pump and compressor motor. So whatever could be gained from the latent heat in the water is lost in energy required by the refridgerant system in the time taken to transfer that heat. So, energy in equals energy out.

 

[rtbcomp]

Maybe, but that "extra" energy still appears as heat at the rear of the fridge, so the total heat output is electrical energy in plus heat taken from the bucket. I.e. you get more heat out than electrical energy in.

You must do, the heat from the bucket has to go somewhere.

IIRC the theoretical conversion factor when compressing gas is 1 KWH of energy required to shift 3 KWH of heat, but in practical terms this is nearer 1:1 as snooper mentioned in post #19.

Perhaps you would like to argue Flash of Light's point in post #54

 

[stuvy]

Thanks for that J_K

 

[J_K]

You're welcome.