FTFS Chap04 P001 - Chapter 4 Energy Transfer by Heat, Work,...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 4 Energy Transfer by Heat, Work, and Mass Chapter 4 ENERGY TRANSFER BY HEAT, WORK, AND MASS Heat Transfer and Work 4-1C Energy can cross the boundaries of a closed system in two forms: heat and work. 4-2C The form of energy that crosses the boundary of a closed system because of a temperature difference is heat; all other forms are work. 4-3C An adiabatic process is a process during which there is no heat transfer. A system that does not exchange any heat with its surroundings is an adiabatic system. 4-4C It is a work interaction. 4-5C It is a work interaction since the electrons are crossing the system boundary, thus doing electrical work. 4-6C It is a heat interaction since it is due to the temperature difference between the sun and the room. 4-7C This is neither a heat nor a work interaction since no energy is crossing the system boundary. This is simply the conversion of one form of internal energy (chemical energy) to another form (sensible energy). 4-8C Point functions depend on the state only whereas the path functions depend on the path followed during a process. Properties of substances are point functions, heat and work are path functions. 4-9C The caloric theory is based on the assumption that heat is a fluid-like substance called the "caloric" which is a massless, colorless, odorless substance. It was abandoned in the middle of the nineteenth century after it was shown that there is no such thing as the caloric. Boundary Work 4-10C It represents the boundary work for quasi-equilibrium processes. 4-11C Yes. 4-12C The area under the process curve, and thus the boundary work done, is greater in the constant pressure case. 4-13C 1 kPa m 1 k(N /m ) m 1 kN m 1 kJ 32 3 ⋅= = 4-1
Background image of page 1

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

View Full DocumentRight Arrow Icon
Chapter 4 Energy Transfer by Heat, Work, and Mass 4-14 Saturated water vapor in a cylinder is heated at constant pressure until its temperature rises to a specified value. The boundary work done during this process is to be determined. Assumptions The process is quasi-equilibrium. Properties Noting that the pressure remains constant during this process, the specific volumes at the initial and the final states are (Table A-4 through A-6) /kg m 1.3162 C 300 kPa 200 /kg m 0.8857 vapor Sat. kPa 200 3 2 2 2 3 kPa 200 @ 1 1 = = = = = = v T P v v P g o P (kPa) V 200 1 2 Analysis The boundary work is determined from its definition to be kJ 430.5 m kPa 1 kJ 1 /kg m 0.8857) 2 kPa)(1.316 kg)(200 (5 ) ( ) ( 3 3 1 2 2 1 1 2 out , = = = = = v v mP V V P dV P W b Discussion The positive sign indicates that work is done by the system (work output). 4-15 Refrigerant-134a in a cylinder is heated at constant pressure until its temperature rises to a specified value. The boundary work done during this process is to be determined. Assumptions The process is quasi-equilibrium.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/14/2008 for the course ME 320 taught by Professor Dr.kinne during the Spring '07 term at University of Texas at Austin.

Page1 / 31

FTFS Chap04 P001 - Chapter 4 Energy Transfer by Heat, Work,...

This preview shows document pages 1 - 3. Sign up to view the full document.

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