Biography of James Watt, Inventor of the Modern Steam Engine

On April 29, 1769, Scottish engineer James Watt's patented a steam engine with a separate condenser enrolled. An excerpt from the article:

"The Watt Steam Engine

Watt came to realize that the greatest fault in the Newcomen steam engine was poor fuel economy due to its rapid loss of latent heat. While Newcomen engines offered improvements over earlier steam engines, they were inefficient in terms of quantity of coal burned to make steam vs. power produced by that steam. In the Newcomen engine, alternating jets of steam and cold water were injected into the same cylinder, meaning that with each up-and-down stroke of the piston, the cylinder’s walls were alternately heated, then cooled. Each time steam entered the cylinder, it continued to condense until the cylinder was cooled back down to its working temperature by the jet of cold water. As a result, part of the potential power from the steam’s heat was lost with each cycle of the piston.

Developed in May 1765, Watt’s solution was to equip his engine with a separate chamber he called a “condenser” in which condensation of the steam occurs. Because the condensing chamber is separate from the working cylinder containing the piston, condensation takes place with very little loss of heat from the cylinder. The condenser chamber remains cold and below atmospheric pressure at all times, while the cylinder remains hot at all times.

In a Watt steam engine, steam is drawn into the power cylinder under the piston from the boiler. As the piston reaches the top of the cylinder, an inlet valve allowing steam to enter the cylinder closes at the same time a valve allowing steam to escape into the condenser opens. The lower atmospheric pressure in the condenser draws in the steam, where it is cooled and condensed from water vapor to liquid water. This condensation process maintains a constant partial vacuum in the condenser, which is passed to the cylinder by a connecting tube. External high atmospheric pressure then pushes the piston back down the cylinder to complete the power stroke.

Separating the cylinder and condenser eliminated the loss of heat that plagued the Newcomen engine, allowing Watt’s steam engine to produce the same “horsepower” while burning 60% less coal. The savings made it possible for Watt engines to be used not just at mines but wherever power was needed.

However, Watt’s future success was in no way assured nor would it come without hardship. By the time he came up with his breakthrough idea for the separate condenser in 1765, the expenses of his research had left him near poverty. After borrowing considerable sums from friends, he finally had to seek employment in order to provide for his family. During a span of about two years, he supported himself as a civil engineer, surveying and managing the building of several canals in Scotland and exploring coal fields in the neighborhood of Glasgow for the magistrates of the city, all while continuing to work on his invention. At one point, a despondent Watt wrote to his old friend and mentor Joseph Black, “Of all things in life, there is nothing more foolish than inventing, and probably the majority of inventors have been led to the same opinion by their own experiences.”

In 1768, after producing small-scale working models, Watt entered into a partnership with British inventor and merchant John Roebuck to build and market full-sized steam engines. In 1769, Watt was granted a patent for his separate condenser. Watt’s famous patent titled “A New Invented Method of Lessening the Consumption of Steam and Fuel in Fire Engines” is to this day considered one of the most significant patents ever granted in the United Kingdom."