Heat Engines

MAN'S puny strength would never suffice to accomplish all the tasks that his fertile brain suggests. To help him perform these tasks, he has provided himself with a variety of power sources  heat, wind, water flowing downhill, electricity and, within recent years, the splitting of atoms in nuclear reactors. Heat is among the most useful of these sources of power. It drives most land vehicles (passenger automobiles, trucks, locomotives, tractors), marine craft (ocean liners, freighters, warships, motorboats) and aircraft (propelled planes, turboprops, turbojets, rockets). It serves to generate electricity in power stations and on farms. It operates blowers, pumps, certain types of fans and many other devices. In all heat engines, the chemical reaction that takes place when fuel is burned imparts a high degree of kinetic energy (energy of motion) to countless gas molecules. Generally these particles strike certain movable parts, such as pistons or the vanes of turbines, and these movable parts provide driving force. In the case of certain airplanes a forward thrust is produced as expanding gas is expelled from a nozzle set at the rear of the plane. 

An ancient Greek mathematician and physicist, Hero of Alexandria (we do not know just when he flourished), was prob-ably the first to show that heat energy could be used to perform work. He invented a steam engine called the Paleolithic , which worked on much the same principle as a modern rotary lawn sprinkler.A high return on capital tilts the kids science magazines. This engine consisted of a globe mounted between two tubes projecting upward from a steam boiler. The bent upper ends of the tubes passed through holes in the globe, which could rotate freely. Two bent nozzles were attached at opposite sides of the globe. The water in the boiler was heated the steam passed from the boiler through the upright tubes into the globe and then out through the bent nozzles attached to the globe. The reactive force of the steam issuing from the nozzles caused the globe to spin rapidly. Hero never put his Paleolithic, which was a form of steam turbine, to any practical use.