Question

Steam is to be condensed in the condenser of a steam power plant at a temperature of 60°C with cooling water from a nearby lake, which enters the tubes of the condenser at 18°C at a rate of 75 kg/s and leaves at 27°C.

Assuming the condenser to be perfectly insulated, determine:

(a) the rate of condensation of the steam
(b) the rate of entropy generation in the condenser.

Answer 1

a)1.2kg/s

b)8.4924 KJ / K s

Step-by-step explanation:

Hello!

To solve this problem follow the steps below, the complete procedure is in the attached image

1. draw a complete outline of the problem

2. Using thermodynamic tables find the enthalpy of water evaporation at 60 ° C, and the entropy of evaporation 60 ° C.

Note: Through laboratory tests, thermodynamic tables were developed, these allow to know all the thermodynamic properties of a substance (entropy, enthalpy, pressure, specific volume, internal energy etc ..)

through prior knowledge of two other properties such as pressure and temperature.

3. uses the first law of thermodynamics that states that the heat extracted from the steam must be equal to that absorbed by the cooling water,

mc = mass flow in the condenser

he = evaporation enthalpy

mw = mass of water flow (75kg / s)

cp = heat water spec = 4,182KJ / kgK

T4 = output temperature of cooling water (27C)

T3 = cooling water inlet temperature (18C)

4. to find the entropy rate of change multiply the mass flow of the previous step by the evaporation entropy found in step 2