04 Thermal cycles

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L.D.D Advanced Building Physics - Thermal cycles - 1693: Torricelli discovered the atmospheric pressure and the principle of the barometer, by constructing what is now called the Torricelli's tube and identifying the Torricellian vacuum. - 1690: Papin introduced the invention of the first atmospheric steam machine, based on the production of vacuum by means of water vapour condensation. - 1698: Savery made the first attempt to use the steam machine to produce work - 1712: Newcomen --> steam condensed by water injection and the piston is pushed down by atmospheric pressure. - 1770: James Watt invented the separate condenser, which leads to an increase in efficiency (the machines operates between two sources of temperature. - 1824: Carnot, hydraulic analogy: the caloric is conserved as the water that moves the blades of a windmill. Reversible cycle: by inverting the direction of the transformation we invert the signs of all the energy exchanges with outside while the modulus is equal. Carnot shows that this is the most efficient cycle. - Nowadays: what is conserved by coming down in a reversible cycle is the entropy 1 - PROPERTIES OF THERMODYNAMIC CYCLES  We called a thermodynamic cycle a transformation for which the evolving fluid exchanges thermal and mechanical energy with the outside but the initial and final state of the evolving fluid coincide. Therefore the evolving fluid of a thermodynamic cycle will be characterised by ΔSM = 0 and ΔUM = 0, since S and U are state functions. Additional assumptions: - The evolving fluid passes through a series of equilibrium states (quasi static transf.) - The evolving fluid represents a closed system Consider to have a thermodynamic cyclic machine M which absorbs heat from a quasi-static heat source HS and performs work on a…