water temp equilibrium time ?

mrbingley · 07-31-2002, 04:18 PM

How long does it take for the water temp to balance with the room temp ?
My first attempt, home made system seems to hold about 1/2 a litre of water, consisting of WB, Fiesta heater matrix, 18inch long, 28mm copper pipe as a reservoir and about 2 metres of tubing, all except the WB in an external case I made, been running for about 2 hrs since I installed it.

Room temp = 23C
System temp = 31C
CPU temp = 42C (idle ?)

Just been using the internet to read this forum, too preoccupied with watching temps to do anything else.
All fans running slowly through a rheostat.

Previous readings with air cooling

Room temp = 23C
System temp = 33C
CPU temp = 52C (idle)

Fans going a lot faster = more noise

A few pictures I took of my setup
http://www.chrisarmitage.pwp.blueyon...ling/index.htm

Cheers
Chris.
PS: Nice and quiet though.

myv65 · 07-31-2002, 04:30 PM

You've got about 1/2 kg of water and it holds ~ 4180 J/kg-°C. One J/s = one watt. So you need about 2090 J of energy to raise your water temperature 1°C. Figure your CPU and pump combine for ~ 100 watts, so every minute you pump about 6000 joules into the water. With no heat transfer from the radiator, it would raise about 3°C per minute. It oughta reach equilibrium within a matter of 1/2 hour easily.

Ohhh, and I noted the ? after your idle temperature. I assume you mean "what's idle". There is no single definition. Unless you're running idling software that truly shuts down the processor when not needed, then idle and load aren't too far apart, say a few watts difference at most.

07-31-2002, 04:18 PM	#1
mrbingley Cooling Neophyte Join Date: Jul 2002 Location: West Yorkshire. UK. Posts: 39	water temp equilibrium time ? How long does it take for the water temp to balance with the room temp ? My first attempt, home made system seems to hold about 1/2 a litre of water, consisting of WB, Fiesta heater matrix, 18inch long, 28mm copper pipe as a reservoir and about 2 metres of tubing, all except the WB in an external case I made, been running for about 2 hrs since I installed it. Room temp = 23C System temp = 31C CPU temp = 42C (idle ?) Just been using the internet to read this forum, too preoccupied with watching temps to do anything else. All fans running slowly through a rheostat. Previous readings with air cooling Room temp = 23C System temp = 33C CPU temp = 52C (idle) Fans going a lot faster = more noise A few pictures I took of my setup http://www.chrisarmitage.pwp.blueyon...ling/index.htm Cheers Chris. PS: Nice and quiet though.

07-31-2002, 04:30 PM	#2
myv65 Cooling Savant Join Date: May 2002 Location: home Posts: 365	You've got about 1/2 kg of water and it holds ~ 4180 J/kg-°C. One J/s = one watt. So you need about 2090 J of energy to raise your water temperature 1°C. Figure your CPU and pump combine for ~ 100 watts, so every minute you pump about 6000 joules into the water. With no heat transfer from the radiator, it would raise about 3°C per minute. It oughta reach equilibrium within a matter of 1/2 hour easily. Ohhh, and I noted the ? after your idle temperature. I assume you mean "what's idle". There is no single definition. Unless you're running idling software that truly shuts down the processor when not needed, then idle and load aren't too far apart, say a few watts difference at most.

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