• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Heat - h1012v1_45
Heat - h1012v1_47

Thermodynamics Heat Transfer and Fluid Flow Volume 1 of 3
Page Navigation
  19    20    21    22    23  24  25    26    27    28    29  
ENERGY, WORK, AND HEAT Thermodynamics As with work, the amount of heat transferred depends upon the path and not simply on the initial and final conditions of the system.   Also, as with work, it is important to distinguish between heat   added   to   a   system   from   its   surroundings   and   heat   removed   from   a   system   to   its surroundings.    A  positive  value  for  heat  indicates  that  heat  is  added  to  the  system  by  its surroundings.   This is in contrast to work that is positive when energy is transferred from the system and negative when transferred to the system.  The symbol q is sometimes used to indicate the heat added to or removed from a system per unit mass.   It equals the total heat (Q) added or removed divided by the mass (m).   The term "specific heat" is not used for q since specific heat is used for another parameter.   The quantity represented by q is referred to simply as the heat transferred per unit mass. (1-16) q Q m where: q = heat transferred per unit mass (Btu/lbm) Q = heat transferred (Btu) m = mass (lbm) Example: Determine the heat transferred per unit mass if 1500 Btu’s are transferred to 40 lbm of water. Solution: Using Equation 1-16 q Q m q 1500  Btu 40  lbm q 37.5  Btu/lbm The best way to quantify the definition of heat is to consider the relationship between the amount of  heat  added  to  or  removed  from  a  system  and  the  change  in  the  temperature  of  the  system. Everyone   is   familiar   with   the   physical   phenomena   that   when   a   substance   is   heated,   its temperature increases, and when it is cooled, its temperature decreases.   The heat added to or removed from a substance to produce a change in its temperature is called  sensible heat.   The units of heat are often defined in terms of the changes in temperature it produces. HT-01 Page 20 Rev. 0







Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.