Sunday 3 February 2013

Thermodynamics in Thermography, Thomas Newcomen and James Watt


In 1712 Thomas Newcomen installed the first practical steam engines, which he called atmospheric engines, to pump water from coal mines. He was not at all the first to attempt this but was the first to succeed at it, and his individual engines were known to work for more than a century.
These were very inefficient but used both coal and water from the mine so no one much cared, they worked! Efficiency increases with their size, and so they tended to make larger and larger engines.
One of the things we Scots do is take other inventions and quite successfully improve them, and so James Watt did just that. Watt was tasked with repairing a Newcomen steam engine operated by Glasgow University he worked at and when he did, he realized the machine wasted about 75% of its energy.
The Newcomen design used the main cylinder both to expand with steam and then to create a vacuum by condensing the steam in the same cylinder wasting all the heat used to heat the cylinder in every cycle. Watt conserved much of this energy by the use of a steam jacket to maintain the heat in the cylinder and extracting the steam to a separate chamber for condensation.
This design allowed for a lot of innovation in the future, including smaller engines which used less coal, and less water, enabling the entire industrial revolution.
Newcomen utilized principles of thermodynamics and engineering that would later be described, but Watt significantly improved these by simply insulating the cylinder and then isolating the condensation.
Twenty eight years ago we were working on diesel powered aircraft carriers both spotting electrical issues, but primarily to resolve heat loss issues. We would identify areas where insulation, or it improvement was needed then calculate the heat loss and savings if the insulation was added, changed, or corrected. The ships wasted heat by it radiating thermal energy from the boilers and pipes, which necessitated its removal in order to make a better working environment, so they paid for the fuel, and then to have the resulting heat removed using large fans to vent the heat into the atmosphere.
This is an interesting parallel to me, with the last name of Newcomb and a Watt as a grandfather.
The US Navy learned the lesson and now pays much more attention to this issue and in the same effort reduces energy loss.
Most thermographic inspections of ships today focus on electrical issues since few ships use much steam today; however, the savings from these inspections have shifted from fuel savings to saving equipment from premature failure.
Have the savings diminished? Not at all, a qualified marine thermographer may inspect 500-900 devices on a ship, reducing maintenance expenses and premature component failures, and prevent several fires each year, and a small fire in the Motor Control Center can cost between one half to one million dollars in damage when all costs are considered returning the investment many times over.

No comments:

Post a Comment