Lecture 13 The State of Principle

# Lecture 13 The State of Principle - Thermal and Fluids...

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Thermal and Fluids Engineering I Prof. Deborah A. Kaminski Lecture 13 – Thermophysical Properties (cont.) Properties of Real Liquids and Solids For an ideal, single-phase material, internal energy is v du c dT = This applies to ideal gases, ideal liquids and ideal solids, but not to two-phase mixtures. If c v is not a function of temperature v ucT ∆= ∆ Enthalpy is related to internal energy by huP v =+ Consider a subcooled liquid beginning at state 1 and ending at state 2 111 v 1 2 v ) 222 v Specific volume is approximately constant for a liquid, so 12 vv == Enthalpy difference is then 21 21 21 () hhuuv PP −=−+ If the process is isothermal, u 1 =u 2 and ( hhv −= isothermal ideal liquid Lecture 12 Page 1

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Thermal and Fluids Engineering I Prof. Deborah A. Kaminski For a real liquid, specific volume and specific internal energy depend mostly on temperature and not on pressure. For example, for liquid water: T °C P kPa v m 3 /kg u kJ/kg 100 101.3 1.043 x 10 -3 419 80 101.3 1.029 x 10 -3 334.9 60 101.3 1.017 x 10 -3 251.1 40 101.3 1.008 x 10 -3 167.5 20 101.3 1.002 x 10 -3 83.8 T °C P kPa v m 3 /kg u kJ/kg 100 101.3 1.043 x 10 -3 419 100 200 1.043 x 10 -3 418.9 100 1000 1.043 x 10 -3 418.7 100 5000 1.041 x 10 -3 417.5 100 15000 1.036 x 10 -3 414.7 For subcooled liquid (, ) () f f vT P v T uT P u T For enthalpy of a subcooled liquid 21 21 21 hhuuv PP −=−+ Let h 1 be a saturated liquid and h 2
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## This note was uploaded on 04/06/2009 for the course ENGR 2250 taught by Professor Borca-tasciuc during the Spring '08 term at Rensselaer Polytechnic Institute.

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Lecture 13 The State of Principle - Thermal and Fluids...

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