ORNL-1771 - Oak Ridge National Laboratory

8. HEAT TRANSFER AND PHYSICAL PROPERTIES
The enthalpies and heat capacities of NaF-ZrF,-
UF, (65-15-20 mole %) were determined; the heat
capacity in the solid state over the temperature
range 90 to 614°C WQS found to be 0.17 cal/g."C,
and the heat capacity in the liquid state over the
temperature range 653 to 924°C was found to be
0.20 cal/g."C. The enthalpies and heat capacities
of LiF-NoF-UF4 (57.6-38.4-4.0 mole %) were also
obtained; the heat capacity in the solid state over
the temperature range 97 to 594°C was found to
be 0.23 cal/g.OC, and in the liquid state over the
range 655 to 916°C it was found to be 0.53
cal/geoC. The thermal conductivities of three
fluoride mixtures in the solid state at normal
temperatures were determined. The conductivity
of NaF-KF-UF4 (46.5-26.0-27.5 mole %) was 0.7
Btu/hrsft2 ("F/ft), that for KF-Li F-NaF-UF4 (43.5-
44.5-10.9-1.1 mole %) was 2.0 Btu/hr.ft* ("F/ft),
and that for LiF-KF-UF, (48.0-48.0-4.0 mole %)
was 1.4 Btu/hnr.ft2 (OF/ft). A new electrical con-
ductivity device has been constructed and has
been successfully checked with molten salts of
known conductivity.
Additional forced-convection heat transfer meas-
urements of molten NaF-KF-LiF (1 1.5-42.0-46.5
mole %) have been made. Measured thermal con-
ductivities and thicknesses of insoluble deposits
on the inner walls of lnconel heat transfer tubes
made it possible to calculate the thermal re-
sistance of the deposit. The calculated value was
in good agreement with values previously deduced
from the heat transfer measurements, A device
for studying the rates of growth of tube-wall de-
posits has been successfully tested with a simple
heat transfer salt. A hydrodynamic flow system
to be used for studying the reflector-moderated
reactor flow structure has been tested. A mathe-
matical study of the temperature structure in con-
verging and diverging channel systems that duct
fluids with volume heat sources has been made.
A study of wall-cooling requirements in circu-
lating-fuel reactors was made.
'W. D. Powers and G. C. Blalock, Meut Capucztzps
o/ Conipositims No. 39 and 101. ORNL CF-54-8-135
(to be issued).
H. F. Poppendiek
Reactor Experimental Engineering Div i si on
PERIOD ENDING SEPTEMBER 70, 1954
PHYSICAL PROPERTIES MEASUREMENTS
Heat Capacity
W. D. Powers
Reactor Experimental Engineering Division
The enthalpies and heat capacities of two fluoride
mixtures have been determined with Bunsen
i ce ca I or i met ers : '
NaF-ZrF4-UF, (65-15-20 mole 70)
Solid (90 to 614°C)
[IT - fiOoC = -3 + 0.17T
Cp = 0.17 5 0.01
Liquid (653 to 924°C)
HT - HogC = 22 + 0.20T
cp = 0.20 5 0.02
LiF-NaF-UF, (57.6-38.4-4.0 mole %)
Solid (97 to 594°C)
HT - Hoot -= G.22(7)T 4 0.0G017T2
Liquid (655 to 976°C)
Cp = 0.22(7) + 0.000331'
Hr - HOoC = -68 + 0.53T
Cp - 0.53 -t 0.04
In these expressions H is the enthalpy in cal/g,
C is the heat capacity in cal/g."C, and T is the
P
temperature in "C. The experimental enthalpy data
for LiF-NaF-UF4 (57.6-38.4-4.0 mole %) are plotted
in Fig. 8.1.
Automatic Simplytrol units have been added to
the calorimeter systems to more accurately control
the furnace temperatures. This modification has
increased the precision of the experimental data.
Currently, enthalpies of a fluoride mixture are
being measured with the copper block calorimeter.
Density and Viscosity
S. I. Cohen
Reactor Experimental Engineering Division
Prel iminary density measurements were made on
rubidium metal, and the density was found to be
represented by the equation
p(g/cm3) = 1.52 - 0.00054 (T - 39°C) ,
127