Size and weight evaluation of insulated cylindrical radiators used in SNAP-8 heat rejection syste

Edberg, J.

Perez, E. F.

English

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OF
C
TM - 345x63-1-108
DATE-22 April 1963
W.O. 0743-05-2000
)C-01T•ODO•)	
SNAP-8
TECHNICAL MEMORANDUM
PREPARED BY: ` E. F. Perez, J. Edberg
ABSTRACT
CYLINDRICAL RADIATOR ANALYSIS WITH INTERIOR INSULATED,
An investigation was made to evaluate the sizes and weights of cylindrical
radiators for use in the SNAP-8 heat rejection system. In this investigation
the radiators were sized to provide the required heat rejection, while opera-
ting with the maximum external heat load from solar and planetary sources,
using OS-124 or NaK as the cooling fluids.
The interiors of the cylinders were considered to be insulated with heat
radiating from the outside surface of the radiation only.
The resulting optimum radiator sizes were compared to an optimum flat
radiator configuration.
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APPROVED:
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DEPARTMENT HEAD'
P. I. Wood
NOTE: This document is considered preliminary and is subject to revision as
analysis progresses and additional data are acquired. The general reader may
encounter internal reference not available to him.
-COPY NO.	 74PAGM
TM 345:63-1-1o8
CYLINDRICAL RADIATOR ANALYSIS WITH INTERIOR INSULATED
I. INTRODUCTION
The flat, hinged radiator, conceived early in the design phase of the
SNAP-8 has several drawbacks. These drawbacks include hinges which are difficult
to fabricate for space applications because of the possibility of cold welding.
The second drawback is that in order to connect the moving radiator panels to
the fixed components in the PCS, it is necessary to use some type of flexible
bellows connection and a mechanical deploying mechanism which would affect
system reliability. Also the lack of rigidity due to the flexible joints could
possibly cause problems in maneuvering in space.
Consequently, it was decided to investigate the possibility of using a
rigid cylindrical radiator which would fit within the envelope of the aero-
dynamic fairing of the S-IV stage of the Saturn C-1 Booster.
Beat rejection from this radiator configuration would be from the outside
surface only, with the interior being insulated to prevent irradiation from the
main radiator onto the lube and cool radiator section, the NS, the PCS and the
payload.
II. TECHNICAL DISCUSSION
A.	 RADIATOR DESIGN CRITERIA
The main heat rejection radiator was designed to provide the neces-
sary area to reject approximately 330 kilowatts (thermal), at temperature levels
corresponding to the current system design points with the radiator inlet and
outlet temperatures at 665°F and 495 0 F, respectively. The lube and cool loop
radiator was designed to reject 17.3 kw (thermal) with the radiator inlet and
outlet temperatures at 250°F and 220°F, respectively. It was further assumed
that the cylindrical radiators would reject heat by radiation from the outer
surface only. Adequate insulation would be provided internally to minimize
heat radiation from hot to cold surfaces. It was assumed that the radiator
would be designed for the maximum external heat flux with the axis of the
cylindrical perpendicular to the solar flux.
W
1
TM 345:63-1-108
Two fluids were considered in the analysis; OS-124 and NaK, the
first being a hydrocarbon ana the second an inorganic liquid metal.
B.	 BASIC ASSUMPTIONS
The analyses were conducted by raking certain simplifying assumptions
and approximations. Some of the more important assumptions are noted below:
1. The main heat rejection radiator and the L/C loop radiator
were assumed to be contained within the 20-ft diameter of the Saturn C-4 envelope.
It was further assumed that the ends of the cylindrical radiators were closed
and no heat would be transferred through them.
2. The minimum fin thickness was assumed to be 0.015 in. from
fabrication and strength considerations. The fin profile was assumed to be
either rectangular or trapezoidal as indicated in the results of this analysis.
3. Calculations of radiator heat rejection were performed using
data, equations and tables developed for flat radiators. Conversion to cylindrical
radiators was accomplished by assuming that the tube and fin could be sectioned
as shown in Figure 1.
4. The micrometeorite armor was assumed to be 0.320 inch thick
and made of castable aluminum. The heat rejection from the fins was determined
using data, curves and equations of Mackay and Bacha, REferenee 1. The effects
of mutual irradiation between tubes and fins was not considered.
5. Longitudinal heat conduction along tubes and fins was not
considered.
6. Fin dimensions were assumed to be constant along the length of
the radiator.
III. METHOD OF ANALYSIS
The method of analysis was similar to that performed in the flat folding
radiator. The procedure followed approximately the following steps.
A.	 The heat rejected from the fin was based on at the armor surface
temperature for each of the 7 nodes into which the entire main heat rejection
radiator was divided. After determining the length of fin required per node
r
2
sum up all the lengths.
B. The weight per unit length of the tube and fin was calculated, then
radiator weight was calculated using the total lengths evaluated previously.
These weights do not include the weight of ma-ifolds or tubes connecting the
radiators to the PCS.
C. The calculations were repeated for radiators having different fin
dimensions.
IV. RESULTS AND CONCLUSIONS
A. The results of calculations for cylindrical radiators using OS-124,
were plotted in Figure 2 which shows radiator weights as a function of fin
dimensions and radiator area.
B. Results of the calculation for cylindrical radiators using NaK are
shown plotted in Figure 4. It is noted that, in all cases calculated in this
study, the fin width of approximately 3.0 inches invariably resulted in the
lightest configurations.
C. A comparison of the weights of the main radiator in cylindrical
configuration for OS-124 and NaK are shown in Figure 3.
D. It may be concluded that cylindrical radiators using NaK coolant
can replace the hinged flat radiator with a very small weight penalty. For
comparison, Table I shows a summary of fin dimension, weights of tubes and fins
and radiator areas for the optimum flat radiators and cylindrical radiators.
3
TM 345:63-1-108
TABLE
Flat	 Cylindrical
Radiator Configuration	 Radiator	 Radiators
Coolant NaK NaK NaK OS-124
Fin width - inches 4.55 3.0 3.0 3.0
Fin thickness at root
, Jr H inches .o64 .06o .04o .06o
Fin thickness at tip
,._ d' c inches .016 .030 .020 .030
Total projected area - ft 1360* 1000** 1110** 1100**
Weight of tubes and fins wlb 880 1120 1050 1240
* Projected area on both sides of flat radiator
** Outside area of cylinder
Reference
D. B. Makay, C. P. Bacha, Space Radiator Design and
Analysis, Part I, ASD Technical Report 61-30, dated
October 1961.
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Cylindrical radiator analysis with interior insulated

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