Coiled section of tubing measures viscous properties of gelled cryogenic propellants under conditions closely resembling flow in rocket engine systems. Characteristic flow curve provides data necessary for the design of prototype hardware systems using the liquid or gel of interest

Globus, R. H.

Vanderwall, E. M.

English

NASA Technical Reports Server

1972	 B72-10180 
NASA TECH BRIEF 
Ames Research Center	 4r 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Cryogenic Gel Flow Viscometer 
The problem: 
To measure the viscous properties of gelled cryo-
genic propellants under conditions closely resembling 
flow in rocket engine systems. 
The solution: 
A coiled section of tubing immersed in the gel 
propellant. 
How it's done: 
The viscometer consists of %-inch copper tubing 
(diameter about 1 cm) . coiled to fit inside a glass 
gelling vessel. The coil diameter is about 100 mm 
and the total length of the tubing is 179.5 cm. The 
inlet to the coil is in the form of an inverted J with 
the entrance near the bottom of the glass gelling 
vessel. The position of the entrance permits the major 
portion of the gel to be used for the measurement; 
it also minimizes coring. Near the entrance to the 
coil is positioned a small tube which injects helium 
into the viscometer tubing. The helium is cooled by 
passing it through a coil of 3-inch tubing (diameter 
about 0.3 cm) which also is immersed in the gel. The 
injection of helium prevents the gel from filling the 
viscometer tube while the gel is being prepared in 
the gelling vessel; thus, there is no need for a valve 
in the flow system. 
The inverted-J inlet section of tubing is followed 
by the coiled section containing the major portion 
of the total length of tubing, and this is followed 
by a straight outlet section which returns to the bot-
tom of the coils and extends through the bottom of 
the glass gelling vessel by means of a ball-socket 
joint (glass to stainless steel).
Two parameters are measured during an experi-
ment with a flow viscometer: the AP across the tubing 
and the flow rate. The parameters are plotted in the 
form of DP/4L versus 8V/D, where D is the dia-
meter of the tubing, L is the effective length of the 
tubing, and v is the velocity at which the gel is 
transferred through the tubing. The velocity is cal-
culated from the measured flow rate. The term 
DAP/4L is commonly known as the shear stress, and 
the term 8V/D is the shear rate. The ratio of shear 
stress divided by the shear rate is the viscosity of 
the fluid at that particular shear rate. The plot of 
the DAP/4L versus 8V/D produces a curve which 
is called the "characteristic flow curve" for the fluid 
being tested. 
The method of data presentation, i.e., the charac-
teristic flow curve, provides data necessary for the 
design of prototype hardware systems using the 
liquid or gel of interest. For example, in the region 
Of laminar flow, if the flow rate and the diameter and 
length of the pipe are known, the pressure drop 
which will occur can be determined from the curve. 
Alternatively, by selection of a pressure drop value 
for a length of pipe and flow rate, the required dia-
meter of pipe can be calculated. Further, because 
the curve provides the viscosity value of the liquid 
over a range of shear rates, the Reynolds number can 
be calculated for the liquid at various flow condi-
tions. Experimentally, the turbulent mode of flow 
can be determined by increasing the flow rate until 
the data display a sharp departure from a smooth 
laminar-flow curve. If the flow measurements are re-
peated with another size of tubing and the flow rate 
(continued overlèaf( 
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is again increased until the turbulent mode is reached, 
the point at which the transition from laminar to 
turbulent flow occurs can be calculated from the 
data for any size piping and flow rate. The turbulent 
flow properties as represented by branches from the 
laminar flow curve can be used for system design 
in the same manner as the data available in the 
laminar region of the curve. 
The only value which is not directly obtainable is 
L, the effective length of the tubing, because flow 
in coils or bends encounters an additional resistance 
over flow in straight tubing. In the laminar region 
the effective length may be calculated from the ex-
pression, L = D2LP/32T1V, using a fluid of known 
viscosity. In the turbulent region, L is calculated 
from the conventional empirical relationships for tur-
bulent fluid flow. 
Reference: 
Globus, R. H.; and Vander Wall, E. M.: System 
Analysis of Celled Space-Storable Propellants. Proc.
AIAA 6th Propulsion Joint Specialist Conference, 
June 15-19, 1970, San Diego, California. 
Note: 
No other documentation is available. Specific ques-
tions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B72-10180 
Patent status: 
No patent action is contemplated by NASA. 
Source: Robert H. Globus and
E. M. Vander Wall of
Aerojet Liquid Rocket Company
under contract to 
Ames Research Center 
(ARC-10528) 
B72.10180
	 Category 08


Cryogenic gel flow viscometer

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