T = T +t,, S
1 N
T=-YT
N-
(54)
t = 4.303
S1N
S2 1(T T)2
N-1
By using these two error calculations the uncertainty can be determined in the
temperature measurements for the larger system. For the smaller system the conduction
error also must be calculated. This error will be based on the conductivity of the heater,
the length of the heater, as well as the heat flux that is provided by the heater. This error
is 1.80F for 1.9 Mbtu/in2-s, 5.5980F for 5.69 Mbtu/in2-s, 7.4520F for 7.58 Mbtu/in2-
s, and 9.3240F for 9.48 Mbtu/in2-s. These are calculated using the conductivity of the
lb
heater which is 2.37 Using these equations the uncertainty of the temperature
s-R
data for the larger system is + 27.828 F, and is + 28.566 F for the smaller system.
For pressure calculations a digital pressure gage is used to measure the static
pressure at the inlet to the apparatus and at the exit. The resolution for these pressure
gages is 0.1 psi and the instrument uncertainty is +1 psi. Using the same process for the
temperature the uncertainty in pressure is 1.479 psi. For the flow measurement the
same process is followed with a resolution of 2 scfm, and instrument uncertainty of +1
scfm which provides a total uncertainty of +1.414 scfm. Using this information the
lb
uncertainty of the heat transfer coefficient is 2.46e-5 for the larger system
ft-s-R
lb
and 2.4e-5 for the smaller system.
ft-s-R