Quote:
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Originally Posted by unregistered
this whole exercise is bothersome.........the first adjustment is to cal in the medium to be measured
(I cal in flowing water, does this mean that my air temps are off ?)
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Bothersome? I find it a bloody nightmare and I am not the tester
Have been busy postponing addressing.
Only posting to show have not "done a runner"
Not yet formulated any translucent thoughts,
Have niggles, though about the initial and dominating coolant Temp correction being +, this appears contrary to Robert J. Moffat expectations: "
The Prandtl numbers of most liquids are greater than 1; hence, the recovery factor a is greater than 1 and
probes tend to read higher than the stagnation temperature in high-speed liquid flows. With thermistors
and RTDs in liquids, the self-heating effect and the velocity error both tend to cause high readings".
Similarly feel the that "air temps are off " maybe correct:
"
In gases, where the Prandtl number is less than 1, the two effects are of opposite sign and may partly cancel
each other."
However need to do some reading
Busy refining and cluttering Model shown in
Post127
From this:
Think the parameters from your data(SD,(C/W)in,and Eff(Fan +Rad)) can be designated a subscript m:
"
Tm: The mixed mean fluid temperature. Used for internal flows where the intent of the calculation
is to describe the changes in mixed mean fluid temperature (e.g., heat exchangers)."
.........."For a given data set, the value of the heat transfer coefficient will depend on the reference temperature
chosen, and h should be subscripted to inform later users which reference was used: e.g., h¥, hm, or adiabatic"
With measured Heat Dissipation ~ 150 to 300w, I think the difference between " mixed mean fluid temperature" and "Adiabatic" parameters is 1.44%(2.16/150) and 1.25%((2.16+1.59)/300)
Have been correcting my Model(adiabatic I think) for the meddlesome dP*Q to obtain a " mixed mean fluid temperature" Model
Have,also, been correcting for "Fan Heating of Air"(2.16w,if present).
Attached .
Not suggesting should read anything into agreement
Edit Corrected Tube Spacing miscalculation in Model