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Bob UK
Unregistered guest
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Posted on Wednesday, 03 December, 2014 - 08:10:   Edit PostDelete PostView Post/Check IP

On my 3 day wonder air con certificate. Heat pumps were briefly explained as a back to front fridge.

Today I got a look at a system made from scrap stuff.

The pump is a Toyota air con compressor from a vehicle. This is driven by a 2 hp single phase 240 vac motor. Belt drive.

The condenser is also a vehicle one and is submerged in a 40 gallon water tank.
The condenser tank is inside the garage with the compressor.

The evaporator is outside the garage also in a 40 gallon water tank.

The gas which is car lpg is pumped through the condenser. Then from the condenser to a restriction, the orifice which is fixed. Then to the evaporator. The orifice is next to the evaporator and under water. The gas then goes to a pot with a dip tube to stop liquid getting to the compressor. ( Which is how I broke my vacuum pump that is really a compressor.)

What happens is that because of the vast specific heat capacity contained in 2 x 40 gallons of water is that the system runs with no controls and heats the water up inside the garage and cools the water outside. Because the system is not powerful enough to boil the water or freeze the water it just runs and runs.

The hot water is then pumped to a radiator in the kitchen. The water is 50c.

I am impressed at the amount of heat it's giving on 1575 watts.

However if the outside temp were to drop to say 5c then the evaporator tank is liable to freeze which will lower the specific heat capacity of that body of water. Ice is quite a good insulator of heat energy.
Plus safety wise I would fit a high pressure switch.

To solve the evaporator problem I would ditch the water and bury the evaporator six foot down and use the ground as a giant heat sink. Trouble is that it's expensive which sort of negates the energy savings. And he doesn't know how to calculate the sizes. Using water means that by adjusting the water levels he can fine tune it, which can't be done once the pipes are buried.

A tuned system can have a coefficient of efficiency of as big as 4.6 to 1. Meaning that for every watt used 4.6 watts of heat is emitted. He reckons he has about 2.5 to 1.

At first it appears to break the laws of thermodynamics. The pump heats up the gas and then steals heat from outside.

Colder just means less heat energy.

Also I think that global warming is also caused by people heating things up. 7 billion people heating stuff is a lot of heat. With heat pumps apart from heating the gas, most of the heat is stolen from outside.

(Message approved by david_gore)
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Jan Forrest
Grand Master
Username: got_one

Post Number: 705
Registered: 1-2008
Posted on Thursday, 04 December, 2014 - 00:42:   Edit PostDelete PostView Post/Check IP

If you bury a series of pipe runs at the depth of just a meter and then fill them with a strong brine solution you can circulate the brine around the garden and use the heat it extracts from the subsoil to keep the 'hot' barrel warm enough to work. Obviously this is only useful in area of the world that are subarctic with no deep permafrost to cope with.

Professional systems like this are available in most such countries, although, as stated, they are horrendously expensive to install. However if you stay in the same house for a decent period of time you can start to break even on the cost in just a few years - depending on the length and depth of the colder seasons.
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Randy Roberson
Grand Master
Username: wascator

Post Number: 327
Registered: 5-2009
Posted on Thursday, 04 December, 2014 - 12:16:   Edit PostDelete PostView Post/Check IP

if you have some pond water you can get the heat from that; well water also. A college in the northern US is air conditioning using cold water from a deep lake (a Great lake I think); it might be Cornell or Purdue, not certain. That is a different issue, though.
As for the ultimate disposition of "all the heat" people use: it is radiated out into space. The global warmists are claiming that the co2 is blocking or reducing this radiation. Maybe, maybe not, but I trust God to handle it rather than some human government all of which tend to become tyrannical and start killing everyone. The sun sends lots more heat to the earth than people contribute anyway.
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Bob UK
Unregistered guest
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Posted on Thursday, 04 December, 2014 - 05:53:   Edit PostDelete PostView Post/Check IP

Also putting anti freeze in the outside tank might work. The tank must be animal proof. Antifreeze is poisonous.

What the guy is trying to do is design a system that is about the same price as a gas central heating system, that is modula and adaptable to different houses.

The hot water tank could also cope with a second condenser in the tank run by a second pump and evaporator. Thus big houses have two pumps and small houses one pump. They must share the same condenser water tank so that the radiators in the house are still on the same circuit. Thus minimal alteration when changing from gas to heat pump.

The reason for two pumps is houses are single phase and big electric motors cause supply problems on start up.

I can't experiment like this because I don't have a gas safe certificate. He's got one.
My certificate is vehicle only And refrigerant handling.

On a new building I would go heat pump and under floor heating.

Also I have been trying to get my head around a Stirling engine. If I drive a Stirling engine will it make lots of heat.

(Message approved by david_gore)
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Bob UK
Unregistered guest
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Posted on Friday, 05 December, 2014 - 09:50:   Edit PostDelete PostView Post/Check IP

Big big very huge large problem.

First a correction not coefficient of efficiency but coefficient of performance.

Although the heat pump is super efficient. Cheaper to buy gas condensing boilers which are not as efficient are cheaper to run in cost per unit of heat.

This fact has shot the heat pump business model down in flames with no survivors.

Except while discussing control circuits we discussed thermo couples. Which produce a voltage.

(Message approved by david_gore)