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Expressing Power Cycle Performance
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
Given that power is the rate of doing work, applying a unit of time to a unit of power yields a measure of work. Hence, hp-h or Wh are the common work units. Given that power already has a unit of time, work expressions can be reduced to basic energy units such as Btu, calorie, or Joule. In many thermodynamic applications, Btu is considered to be a more convenient English system unit than ft-lbf. In terms of potential work energy, it is defined by the relationship 1 Btu = 778.16 ft-lbf. One hp is approximately equal to 2,545 Btu. The Joule, which may be considered the mechanical equivalent to heat, is equal to 4.1855 calories.
An overview of thermodynamics
Published in W. John Rankin, Chemical Thermodynamics, 2019
Drawing on previous work, in 1824 Sadi Carnot, a French military engineer and physicist, published the book Reflections on the Motive Power of Fire which outlined the basic energy relations between heat engines and motive power. It anticipated the second law of thermodynamics and marked the start of thermodynamics as a modern science. In 1843 James Joule, an English physicist from a wealthy brewing family, published a paper Mechanical Equivalent of Heat which anticipated the first law of thermodynamics. The first and second laws of thermodynamics emerged in a formal sense in the 1850s primarily out of the works of William Rankine (a professor of civil and mechanical engineering at the University of Glasgow), Rudolf Clausius (a German physicist) and William Thomson (later Lord Kelvin). The first textbook of thermodynamics, published in 1859, was written by William Rankine.
Analysis of Thermal Energy Systems
Published in Steven G. Penoncello, Thermal Energy Systems, 2018
In 1845, James P. Joule published a paper entitled, “On the Mechanical Equivalent of Heat”. Joule’s work was the foundation for the first law of thermodynamics. From 1850 to 1865 several individuals including Sadi Carnot, William Thomson (Lord Kelvin), William Rankine, and Rudolph Clausius developed the ideas that would eventually become the second law of thermodynamics. In 1865, Clausius proposed a new transformational property, entropy, and its relationship to heat as energy. These famous works are the basis of how we understand heat (as energy) in the first and second laws of thermodynamics today.
History of ‘temperature’: maturation of a measurement concept
Published in Annals of Science, 2020
In 1843, unaware of Mayer’s proposal, James Prescott Joule, a 25-year-old brewer’s son in Manchester, England, began direct measurements of the ‘mechanical equivalent of heat’. He rigged a falling weight to drive a set of paddles in a vat of water. Stirring the water increased its temperature. Joule measured how far the weight would fall for each 1° increase in water temperature. His first result was that a weight of 896 pounds falling one foot would raise the temperature of one pound of water by 1° Fahrenheit. Subsequent results, with increasingly sophisticated methods, were 1001, 1040, 910, 1026, 587, 742, and 840 foot-pounds.103 Despite the erratic results, Joule was convinced there is in nature a single determinate ratio at which mechanical work can be converted to heat. By May 1845, he was confident that the correct number was about 800. On Thursday June 24, 1847, in a presentation to the Oxford meeting of the British Association, he claimed the mechanical equivalent of heat was 775.4 foot-pounds per pound of water per degree Fahrenheit. Illustrious members of his audience included John F. W. Herschel, William Whewell, Charles Wheatstone, and the mathematician Baden Powell.104 But the audience member who would turn out to be the most important for spreading Joule’s proposal was William Thompson, who would celebrate his twenty-third birthday two days later. The two young men became close collaborators.
Robert Hare's Theory of Galvanism: A Study of Heat and Electricity in Early Nineteenth-Century American Chemistry
Published in Ambix, 2018
In 1870, James Joule won the Royal Society of London’s prestigious Copley Medal for his contributions to the development of thermodynamics. His research on the mechanical equivalent of heat provided an empirical basis for a new conceptual framework in physical science, one grounded in the study of the conservation of and conversion between different kinds of energy.2 Although perhaps best known for his paddle-wheel experiment, in which he showed that mechanical motion could be converted into heat, his earliest research focused on the properties of electrochemical cells, especially the amount of heat and electricity they produced.3 In his unpublished laboratory notebooks on the subject, Joule referenced works by Michael Faraday, Robert Hare, and others.4 While Faraday’s work is well known to historians, Hare’s contributions to the study of heat and electricity are not. Who was Robert Hare, and why were physicists like Joule interested in his research?