Question

4.54 Saturated liquid nitrogen at 600 kPa enters a boiler at a rate of 0.008 kg/s and exits as saturated vapor (see Fig. P4.54). It then flows into a superheater also at 600 kPa, where it exits at 600 kPa, 280 K. Find the rate of heat transfer in the boiler and the superheater.

Answer 1

Answer:

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answer :

i) 1.347 kW

ii) 1.6192 kW

Explanation:

Attached below is the detailed solution to the problem above

First step : Calculate for Enthalpy

h1 - hf = -3909.9 kJ/kg ( For saturated liquid nitrogen at 600 kPa )

h2- hg = -222.5 kJ/kg ( For saturated vapor nitrogen at 600 kPa )

second step : Calculate the rate of heat transfer in boiler

Q1-2 = m( h2 - h1 )  = 0.008( -222.5 -(-390.9) = 1.347 kW

step 3 : find the enthalpy of superheated Nitrogen at 600 Kpa and 280 K

from the super heated Nitrogen table

h3 = -20.1 kJ/kg

step 4 : calculate the rate of heat transfer in the super heater

Q2-3 = m ( h3 - h2 )

        = 0.008 ( -20.1 -(-222.5 ) = 1.6192 kW