Chapter 6, Problem 6.75P

Interpretation Introduction

Interpretation:

Determine the mass flow rate of water if it is sprayed into a stream of superheated steam in an account such that a single stream of saturated vapor stream is formed in a desuperheater. Also find$\stackrel{•}{S_G}$for this process and comment on irreversible feature of the process.

Concept Introduction:

For liquid water in beginning of operation, we use entropy and enthalpy equations for calculation of enthalpy and entropy at given conditions and these equations are:

  $dH=C_{P}dT+\left(1-\beta T\right)VdP$

  $dS=C_P\frac{dT}{T}+\beta VdP$

Since given problem is associated with both mass and energy changes, so we consider general energy balance here which is defined as:

  $\frac{d{\left(mU\right)}_{\text{tank}}}{dt}+\Delta \left[\left(H+\frac{1}{2}{U}^2+zg\right)\stackrel{•}{m}\right]=\stackrel{•}{Q}+\stackrel{•}{W}$                   ....(1)