A TIM C/W number.

[BillA]

they must converge, eh ?

[Les]

Originally Posted by unregistered

they must converge, eh ?

Not when C/W is measured with reference to inlet temperature.
The lower Specific Heat of the Antifreeze mixture should keep its C/W vs LPM curve, as LPM approaches zero, above that of pure water.

[BillA]

I unnastan, but that difference approaches zero as well
is this difference measureable ?
the LMTD is better for this I think

[Les]

Originally Posted by unregistered

is this difference measureable ?
the LMTD is better for this I think

Dunno,but will do sums.
Not sure LMTD is better.
Anyone considering the theory will be aware that heating of coolant has to be taken into account.
For system calculations the use of inlet temperature is the most convenient.
So no, "C/W" with reference to inlet temperature is preferred.

[Roscal]

Agree with Les. LMTD is useless IMO and it's only another mathematical expression to show others things but don't change the reality. All we need is inlet T°, wattage and flowrate to describe perf (easily measured). A single description of the coolant used is enough to get (and understand) the whole thermal behaviour of any WB for a given fluid.

[Les]

Originally Posted by unregistered

is this difference measureable ?

Think not.
Probably 95% Specific Heat and possibly 99-105% Density of water (here and here
Worst case :

[Les]

Same model as here
Imput values :
Water :- Cg=4171w/kg, Density=998.2kg/m^3, Cond=0.599w/m*c, Kinematic Viscosity=1.006e-6 m/s, (Calculated Thermal Diffusivity= 1.430e-7m^2/s, Calculated Prandtl No=6.99)
15% Antifreeze:- Cg=3962.w/kg, Density=998.2kg/m^3 Cond=0.545w/m*c,Kinematic Viscosity= 4.353e-6 m/s, (Calculated Thermal Diffusivity= 1.378e-7m^2/s, Calculated Prandtl No= 31.59)
Values possibly a bit ugh but......

[BillA]

0.004-5 °C/W diff @ 4lpm ?
seems a bit much (but I've never used 15% - or even 0.5% antifreeze)
HydrX is 0.3% ethylene glycol when mixed per inst

I have chillers with antifreeze, next fill I'll make a 15% soln and we can ck the theory

[Les]

Originally Posted by unregistered

0.004-5 °C/W diff @ 4lpm ?
seems a bit much (but I've never used 15% - or even 0.5% antifreeze)

That is value my sums give.
Incoherent's measured value is more like 0.003 - Incoherent's data

[BillA]

hmmm
you have more confidence in your calcs ?

[Les]

No, but think they ballpark.

[Incoherent]

Originally Posted by Les

That is value my sums give.
Incoherent's measured value is more like 0.003 - Incoherent's data

I'll clean some of this data up later using an average of many measurements for the water only.
Also I am not sure about the antifreeze. The Swedish part of the product description (which I can read) makes no mention of strength but the danish (which I cannot read properly) section mentions "60-100%" I don't quite know what this means. If the solution is already lower than 100% perhaps the numbers make some sense.
There is the problem of my flowrate calculation. A fairly small shift (left or right on the graph) could affect the values. Flow measurement is a problem. Some methods work well at low flowrates, some at high, none work well over the whole range. Been bugging me for a while.
Some more work is clearly needed. I will try and improve the resolution of my pressure drop sensor. Currently it is about 0.12kPa, way too low resolution for the lower flowrates.

Not this weekend though. I'm off to Riga, Latvia.