Page 122 - DJJ20063- Thermodynamics 1

DJJ20063- Thermodynamics 1

3.2.6 Determine and explain the steady flow energy equation (negligible

change in kinetic or potential energy) leading to the concept of enthalpy -

typical applications such as turbine, compressor, boiler, nozzle, diffuser

and heat exchanger.

a ) STEADY FLOW PROCESSES

In heat engine it is the steady flow processes which are generally of most interest. The

conditions which must be satisfied by all of these processes are :

i. The mass of fluid flowing past any section in the system must be constant
with respect to time.

ii. The properties of the fluid at any particular section in the system must be

constant with respect to time.

iii. All transfer of work energy and heat which takes place must be done at a
uniform rate.

A typical example of a steady flow process is a steam boiler, operating under a constant

load as shown diagrammatically in Fig.3.2.10-1. In order to maintain the water level in the

boiler, the feed pump supplies water at exactly the same rate as that at which steam is
drawn off from the boiler. To maintain the production of steam at this rate at a steady

pressure, the furnace will need to supply heat energy at a steady rate. Under these

conditions, the properties of the working fluid at any section within the system must be
constant with respect to time.

STEAM

OUT
WATER

BOUNDRY
WATER

FURNACE
Figure 3.2.6-1 Steam Boiler

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