Page 11 — The Tribal Messenger
The condenser may have to be considerably higher than the top of the eduction tube to give the propellant the necessary head to force it back again into the bottom of the eduction tube. This, of course, depends on the relative specific gravities of the circulating liquid and the propellant. Another matter is the miscibility of the two liquids — highly immiscible pairs such as hexane-water and carbon tetrachloride-water are best. The temperature at which the propellant boils at a given pressure can be found by checking the vapor pressure of the azeotrope formed by the two components.
Bubbles are like negative weights — they rise in liquids with a force equal to the weight of the liquid they displace. Bubbles of compressed air have been used to pump water and oil out of wells (see Air Lift Pumps, Kent's Mechanical Engineer's Handbook, sec. 2-74) and Pumping by Compressed Air (Edmund B. Evans, John Wiley, 1914).
There is a need for engines that work between slight differences in temperature to operate pumps and control mechanisms which are part of solar heating systems. To make compressed air one needs an air compressor — however, bubbles of other gases can be made without a compressor. If the liquid to be pumped is hot and another propellant liquid with a low boiling point is introduced into the hot liquid, bubbles of gas of the propellant liquid are formed, and these can be used in place of compressed air.
At the top of the eduction tube (the tube within which the bubbles rise) place a condenser at a lower temperature than the circulating liquid and its gas bubbles — the propellant liquid condenses and then returns by gravity to the bottom of the eduction tube where it begins the cycle again.
EDUCTION PUMP FOR CIRCULATION — In past articles I have mentioned two engines that are especially useful: the freon control mechanism that operates the skylid (repeating its power cycle usually only once a day); and the convection engine. Hot air rising, cool air sinking — a properly designed convective air loop rock storage system can eliminate the need for a ½ hp motor. A bubble-operated heat engine can be used merely to circulate liquid in a heat exchange system or a turbine can be put into the circulating loop (see fig. 2) and mechanical energy can be extracted. With sufficient heat the theoretical efficiencies of such a heat engine are as high as 70% of the max Carnot efficiency; with circulating liquid 200°F and condenser 100°F an engine efficiency of 10% should be possible. Again multiplying by eduction pump 70% and turbine 90%, an efficiency of over 6% is possible.
© 1973 by Steve Baer
Source: The Tribal Messenger, Oct 10–23, 1973. Text from embedded PDF.
PDF: 1973-10-10-tribal-messenger.pdf