WE HAVE JUST COMPLETED A THOROUGH REVIEW OF ALL FACTORS INFLUENCING THE SELECTION OF A SUITABLE WHEEL DIAMETER FOR THE MODEL 1 BLOWER.

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03642A001600040036-1
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 5
• Document Creation Date: December 27, 2016
• Document Release Date: September 18, 2012
• Sequence Number: 36
• Content Type: MEMO

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Declassified and Approved For Release 2012/09/18 : CIA-RDP78-03642A001600040036-1
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Dear Sir:
,
We have just completed a thorough review of all factors influ-
(encing the selection of a suitable wheel diameter for the Model 1 blower)
In view of your impending visit here on February 27,.we are summarizing
our findings in this letter, to aid in the discussion of blower per-
formance, power requirements, and the associated burning rates. Information
on motors and switch gear for 50/60-cycle operation is not included, but
will be discussed on February. 27.
From the data shown in Table 1, we believe that a 15-1/2-inch
wheel diameter is an excellent choice for this application. It meets all
of the power requirements and maintains the desired burning rate, except
for an 'estimated reduction of 5 per cent in burning rate at the 50-cycle i
speed when a long stack is used. A wheel diameter larger than 15-1/2 inch
would require a motor larger than 7.5 hp for 60-cycle operation (in addition
to good 50-cycle operation).
This 5 per cent reduction in burning rate can be avoided if the
diameter of a long stack is increased to about 24 inches to reduce gas
velocity and pressure drop. The "long stack" assumed for this calculation
would be equivalent to about 160 feet of straight, round: pipe of
16-inch diameter, or 50 ft of pipe with four 45-degree elboris and three
90-degree elbows, similar to that installed on your first Model 2 unit.
The short stack used for the calculations is a straight length of 16-inch-
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diameter pipe, 6 feet long. Of course, intermediate lengths of stack would
result in intermediate burning rates between +3 per cent and -5 per cent
A
of normal for 16-inch-diameter stacks. A 21 foot length of straight
16-inch pipe has the same flow resistance as one 90-degree elbow.
The term,:..normal burning rate, in Table 1 represents the average
rate from past experience with the second Model 1 unit for the 60-cycle,
5500 rpm blower with the 14-1/2-inch-diameter wheel. The average rate
depends upon the type of paper, of course, but it is assumed that any
variation of air flow will result in a proportionate'variation in burning
rate, regardless of paper type.
Barometric pressure, altitude, and air temperature affect air
density which, in turn, influences air flow, pressure, and power require-
ments of any blower. It was decided that burning rates would be based on
blower performance with air at 80 F and at .a barometric pressure normal
for 1000 ft altitude. Suitable corrections were applied to experimental
data and to the data supplied by the blower manufacturer to convert all
data to this base condition. Experimental burning rates were obtained under
essentially these conditions. turther information on the effect of much
higher altitudes will be discussed on February 27.
Figure 1 is a set of curves showing the relation of blower
horsepower and static pressure to flow rate and to flow resistance of the
incinerator and stack. The upper curves show the relation of horsepower
to flow rate for three wheel diameters at 50- and 60-cycle motor speeds.
The intermediate curves show the relation of static pressure to flow from
Declassified and Approved For Release 2012/09/18 : CIA-RDP78-03642A001600040036-1 "17
Declassified and Approved For Release 2012/09/18: CIA-RDP78-03642A001600040036-1
varies directly as the air mass flow rate. This assumption has not been
verified experimentally, but is reasonably accurate over the narrow range
of interest here.
All of the values in Table 1 were obtained from Figure 1.
As you can see by study of Figure 1, if the blower is to be
mounted on the motor shaft and driven at synchronous speed, increasing
wheel diameter increases power consumption and flow rate. To eliminate
the 5 per cent reduction of burning rate under the worst condition
a slightly larger blower wheel and
considered for 50-cycle operation would require use of.a larger motor to cover
the power requirements for 60-cycle operation. We believe that it may
be preferable to use a stack of larger diameter and low flow resistance
for those few marginal installations where the 5_per cent reduction in
burning rate may occur, and where it is undesirable.
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Declassified and Approved For Release 2012/99/18: CIA-RDP78-03642A001600040036-1
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