1b-r - Conservation of Energy Chapter One Section 1.3...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Conservation of Energy Conservation of Energy Chapter One Chapter One Section 1.3 Section 1.3
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Alternative Formulations Alternative Formulations Time Basis: At an instant or Over a time interval Type of System: Control volume Control surface An important tool in heat transfer analysis, often providing the basis for determining the temperature of a system. CONSERVATION OF ENERGY (FIRST LAW OF THERMODYNAMICS)
Background image of page 2
At an Instant of Time: Note representation of system by a control surface (dashed line) at the boundaries. Surface Phenomena , energy transfer across the control su : rate of thermal and/or mechanical due to heat transfer, fluid flow and/or wor rfa k i c nteract io . e ns in out E E g g Volumetric Phenomena : rate of due to conversion from another enegy form (e.g., electrical, nuclear, or chemical); energy conversion proc thermal ener ess occurs w gy generatio ithin the sy e n m. st g E g energy storage in the system : rate of change . of st E g Conservation of Energy in out g st dE st dt E E E E - + = g g g g (1.11c) Each term has units of J/s or W. APPLICATION TO A CONTROL VOLUME Over a Time Interval Each term has units of J. in out g st E E E E - + = (1.11b) CV at an Instant and over a Time Interval
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
At an instant t dU q W dt - = g Special Cases (Linkages to Thermodynamics) (i) Transient Process for a Closed System of Mass ( M) Assuming Heat Transfer to the System (Inflow) and Work Done by the System (Outflow). Over a time interval tot st Q E W - = ∆ (1.11a) Closed System For negligible changes in potential or kinetic energy t Q W U - = ∆ Internal thermal energy
Background image of page 4
Example 1.3: Application to thermal response of a conductor with Ohmic heating (generation): Involves change in thermal energy and for an incompressible substance. t dU dT Mc dt dt = Heat transfer is from the conductor (negative ) q Generation may be viewed as electrical work done on the system (negative ) W g Example 1.3
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Example 1.4: Application to isothermal solid-liquid phase change in a container: Latent Heat of Fusion t 1at sf U U M = ∆ = h Example 1.4
Background image of page 6
(i) Steady State for Flow through an Open System without Phase Change or Generation: ( 29 flow o w rk pv ( 29 enthalp y t u pv i + ≡ → ( 29 ideal gas constant specific h For an w eat ith : in out p in
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/21/2009 for the course MAE 310 taught by Professor Kuznetsov during the Spring '08 term at N.C. State.

Page1 / 16

1b-r - Conservation of Energy Chapter One Section 1.3...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online