Ultrasonic2's TEC liquid chilled pc

[bds71]

OK - some things are becoming clearer, but some things just aren't quite clicking - hope i don't sound like a broken record here (especially on the last part) - eventually, i'll just click the "i-believe" button and that will be that....but for now, i want to take another stab at it....

interestingly applying 50% of Imax while applying Umax like a pwm controller at 50% is not the same thing as applying 50% of umax

you lost me - current follows voltage: by decreasing voltage, you will decrease current. whether you reduce UMax with a PWM, or by putting 2 TEC's in series, or simply by putting a resistor/potentiometer in front of the TEC the current should decrease proportionately with the voltage??

placing TEC next to each other increases the Qmax while stacking decreases it. (relative to a single TEC)

increasing QMax is a good thing, yes??

PMax is 35V*20A Pmax is the power required to achieve dtmax (no load applied )

this does not compute: 35*20=700; UMax=403 w/dT=67. dT is reached at UMax, not PMax?? question: if i applied 24V@17A (ie:~400W - UMax) would i hit QMax? <confused>

not having the cold side rad and simply decreasing the input voltage further would be a better way to increase COP

decreasing input voltage decreases dT. increasing cold side decreases dT. all things being equal, i don't think the TEC can distinguish between the two methods so CoP should be the same regardless how its done?

you've just created a loop . tec's move heat to the hot side which gets put into the air via the rads. then on the cold side this air and heat is then put back into the cold side via the rads. The TEc's then move it back to the hot side. it's a ever worsening situation that never ends.

at idle, the situation would be as you state - the radiator would be adding heat to the system (assuming TECs would normally operate below ambient). but at load you have more heat coming from the sources than you do being input from ambient air cooling of the rads (ie: the amount of heat being generated by all the sources - in my case 2x OC GPUs and an OC CPU) would bring a normal water loop above ambient. at **that** point the TECs are adding to the efficiency of the cooling loop to maintain ambient - ie: the radiator is no longer adding heat to the system, but hepling to take heat out of the system. once you reach equalibrium (ambient) the radiator no longer acts as a heat source. at that point it creates a base-line for the TEC to hit. and with the low dT you can easily maintain the hotside within 2-5C of ambient.

i think your scenario assumes that the TECs would be able to **hold** subambient even under load (which is what we all strive to accomplish). in that case, yes - the rad would be adding heat to the loop. (sorry, i'm just working through this as i type this lol)....let me get back on this...more to follow - feel free to comment on previous remarks!!

note: if anyone else wants to chime in on the discussion (keep bashing to a minimum please) please do!!

[Ultrasonic2]

OK - some things are becoming clearer, but some things just aren't quite clicking - hope i don't sound like a broken record here (especially on the last part) - eventually, i'll just click the "i-believe" button and that will be that....but for now, i want to take another stab at it....




you lost me - current follows voltage: by decreasing voltage, you will decrease current. whether you reduce UMax with a PWM, or by putting 2 TEC's in series, or simply by putting a resistor/potentiometer in front of the TEC the current should decrease proportionately with the voltage??



increasing QMax is a good thing, yes??



this does not compute: 35*20=700; UMax=403 w/dT=67. dT is reached at UMax, not PMax?? question: if i applied 24V@17A (ie:~400W - UMax) would i hit QMax? <confused>



decreasing input voltage decreases dT. increasing cold side decreases dT. all things being equal, i don't think the TEC can distinguish between the two methods so CoP should be the same regardless how its done?



at idle, the situation would be as you state - the radiator would be adding heat to the system (assuming TECs would normally operate below ambient). but at load you have more heat coming from the sources than you do being input from ambient air cooling of the rads (ie: the amount of heat being generated by all the sources - in my case 2x OC GPUs and an OC CPU) would bring a normal water loop above ambient. at **that** point the TECs are adding to the efficiency of the cooling loop to maintain ambient - ie: the radiator is no longer adding heat to the system, but hepling to take heat out of the system. once you reach equalibrium (ambient) the radiator no longer acts as a heat source. at that point it creates a base-line for the TEC to hit. and with the low dT you can easily maintain the hotside within 2-5C of ambient.

i think your scenario assumes that the TECs would be able to **hold** subambient even under load (which is what we all strive to accomplish). in that case, yes - the rad would be adding heat to the loop. (sorry, i'm just working through this as i type this lol)....let me get back on this...more to follow - feel free to comment on previous remarks!!

note: if anyone else wants to chime in on the discussion (keep bashing to a minimum please) please do!!

you lost me - current follows voltage: by decreasing voltage, you will decrease current. whether you reduce UMax with a PWM, or by putting 2 TEC's in series, or simply by putting a resistor/potentiometer in front of the TEC the current should decrease proportionately with the voltage??

right lets use this tec as an example
243 Qmax
15.2 Umax
26 Imax
Pmax is therefore 395watts

if you apply Umax(15.2) then amps will Be Imax (26) and Pmax will be consumed (395)

50% PWM Current while applying Umax will be 15.2v * 13amps so consumed power is 197.5watt

If you apply 50% of Umax or 7.6v then amps is 11.19 so watt used is 85watts



If you bin the extra complexities of a TEC right now and just use ohms law for a given resistance then the same is true

Resistance of 5 ohms with 12 volts = 2.4 amps and therefore wattage is 28.8 watts

if we then 50%pwm (only allow it to draw 1/2 the current it wants to draw) the current or apply 1/2 of it we get 5 ohms 12v and 1/2 of 2.4amps (1.2) so wattage is 14.4watts

However if we apply 1/2 the volts 6 to a 5ohms resistance we get 1.2amps for a wattage of 7.2watts


SOO no matter what you do you should always apply the lowest input voltage as possible for maximum COPs




increasing QMax is a good thing, yes??

YES

[Ultrasonic2]

i think your scenario assumes that the TECs would be able to **hold** subambient even under load (which is what we all strive to accomplish). in that case, yes - the rad would be adding heat to the loop. (sorry, i'm just working through this as i type this lol)....let me get back on this...more to follow - feel free to comment on previous remarks!!

note: if anyone else wants to chime in on the discussion (keep bashing to a minimum please) please do!!

Right this comment of yours from the previous reply through me why not put a radiator in teh cold loop? by doing so you would increase the cold side of the TEC to ambient

but at load you have more heat coming from the sources than you do being input from ambient air cooling of the rads (ie: the amount of heat being generated by all the sources - in my case 2x OC GPUs and an OC CPU) would bring a normal water loop above ambient. at **that** point the TECs are adding to the efficiency of the cooling loop to maintain ambient - ie: the radiator is no longer adding heat to the system, but hepling to take heat out of the system. once you reach equalibrium (ambient) the radiator no longer acts as a heat source. at that point it creates a base-line for the TEC to hit. and with the low dT you can easily maintain the hotside within 2-5C of ambient.

Yes you are right. and that would make scene if you didn't have enough Qmax to cool the total load via the TEC's

thats the idea my hybrid block works on .. TEC can't move all the wattage, but can say move 1/2 of it so the load applied to the cold side rad is 1/2 what it would be without the TEC's on and therefore the rise above ambient for the cold side is only 1/2


2 things work against you though

1 if you have one rad in the cold side loop and one in the hot side TEC loop, then you could 1/2 your delta by simply having both rads in the cold side loop and not bother with the TEC's

2 the TEC's are using power and therefore heating up your room resulting in a increase in ambient that you wouldn't see without the TEC's on

[bds71]

if we then 50%pwm (only allow it to draw 1/2 the current it wants to draw) the current or apply 1/2 of it we get 5 ohms 12v and 1/2 of 2.4amps (1.2) so wattage is 14.4watts

i could have this wrong, but wouldn't it actually be:

P=I*I*R (I^2*R) so P at PWM 1/2 I (I=2.4) = 1.2*1.2*5=7.2W (not 14.4W)

and likewise (as you stated i the next step) P=(V/R)*V so P at PWM 1/2 V (V=12V) = 6/5=1.2*6=7.2W

Current follows Voltage and Voltage follows Current - if you 1/2 one, you have to 1/2 both.

but i get what your saying: for best COP you want the lowest Voltage (probably between 20-30% UMax). in this regard 3-4 TEC's wired in series would give the appropriate COP - then wire another 3-4 "sets" in parallel to boost dT and keep COP's high (yea, 12-16 TEC's) to get the best performance!! <light bulb comes on> that's why my Boreas (using 12 TECs) only consumes about 10-12A @ 12V (120W) (MUCH higher COP) and will WAY outperform the two 10A/12V (240W) TEC's i bought. i get that now - lesson learned now i just have to buy 14 more TECs and a whole lot of copper lol