421 East 24th Street, Holland MI 49423
616.396.9550 fax 616.396.9665
To: Patrick O’Leary, Futura Corp.
From: James Rasmusson, Retronix Inc.
Re: Results of air flow tests
This letter is a summary of the preliminary testing on convective air flow through the Panel embodiment prototype done jointly by Retronix Inc. and Future Corp. The Panel was affixed to a testing shed.
The air flow was measured by a Davis Turbo Meter which was mounted at the outlet port of the Roof Air Duct. The mounting necessitated having the meter cradled in a block of foam which had a cutout into which the meter fit snuggly. The outside contour of the foam block was circular and dimensioned to be slightly larger than the outlet port diameter so that the block could be snugly pressed into the outlet port. Specifically, the outlet port had a diameter of 20cm and the turbine cowling had a diameter of 6cm. The affect of this restricted air flow will be discussed and compensated for later on in this report.
Our tests indicated an air flow of 2.5 meters per second through the meter under clear sky/ mid day conditions. The air temperature was monitored at three separate locations in the testing shed. The temperature of the exhausted air was l25 degrees Fahrenheit and the ambient temperature was 85 degrees.
The volume of the air flowing through the meter, per second, was 2355 cm3. Factoring the density of air at 125 degrees Fahrenheit, the weight of the exiting air, per second, is computed to be .0041 Kg. At 125 degrees Fahrenheit, air has a Specific Heat of .0042 kilojoules per kilogram. Converting to English units, the Specific Heat loss is .004 BTU’s per second, .24 BTU’s per minute, and 14.4 BTU’s per hour.
The constriction and resulting loss of air volume caused by a column of air going through a “Square Edged Orifice” (non Venturi opening) is significant; in our test setup the air want from a 20cm diameter conduit into a 6cm diameter conduit. For these abrupt conditions, if the small diameter is at least 25% as large as the large diameter, the loss of air volume is computed by multiplying the meter reading by an “Orifice Coefficient’ of .60. Our test setup had a ratio of 6cmI 20cm = .30, well within the 25% lower limit.
This means that the above BTU loss numbers can be multiplied by the reciprocal of the Orifice Coefficient, 1/.60 = 1.666.
The compensated values for Specific Heat loss of the column of air through our testing setup would thus be .007 BTU’s per second, .4 BTU’s per minute, and 24 BTU’s per hour.
Our 4.5’ x 4.5’ testing shed has a surface area of only 20 ft2. A typical building with a 100’ x 100’
roof would have 500 times more surface than our testing shed and would consequently dump 500
times more BTU’s per unit of time. This works out to a very respectable 12000 BTU’s per hour.