TITLE.PM5

FIRST LAW OF THERMODYNAMICS 187

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/M-therm/Th4-5.pm5

2. Constant pressure Heating or Cooling. Fig. 4.59 (a), (b) and (c) shows the constant
   pressure heating process on p-v, T-s and h-s diagrams respectively.
   Generation of steam in the boilers is an example of constant pressure heating.
   Applying first law of thermodynamics, we have

Q = ∆u + pdv.

1

2

z

= (u 2 – u 1 ) + p(v 2 – v 1 ) = (u 2 + pv 2 ) – (u 1 + pv 1 ) = h 2 – h 1

(a)

(b)