A pipe operates at steady-state, steady-flow conditions. Steam enters the pipe at 300°C and 250 kPa, and exits at 250°C and 200 kPa. The volumetric flow rate of the steam entering the pipe is 1.2 m3/s. Assume that there are no work interactions.
(a) Determine the heat transfer rate to or from the pipe.
(b) Using your equations, plot the rate of heat transfer for the same inlet conditions and outlet pressure, but for outlet
temperatures varying from 150°C to 350°C.
Given: V?1 = 1.2 m3/s; T1 = 300°C; P1 = 250 kPa; T2 = 250°C; P2 = 200 kPa
Steady-state, steady-flow; (Inlet = State 1; Outlet = State 2)
Assume: W?= 0 ; neglect changes in kinetic and potential energy
What will be an ideal response?
(a) For a single inlet, single-outlet, steady-state, steady-flow device:
With no power, and no changes in kinetic and potential energy:
Q? = m? (h2 ? h1)
The mass flow rate can be found from the volumetric flow rate of the inlet:
m? =V?1/v1
The specific volume of the inlet, and the enthalpy values of the inlet and outlet can be found with on-line property program:
v1 = 1.0517 m3/kg
h1 = 3070.85 kJ/kg
h2 = 2971.26 kJ/kg
So, m? = (1.2 m3/s) / (1.0517 m3/kg) = 1.14 kg/s
Q? = (1.14 kg/s)(2971.26 – 3070.85)kJ/kg = -114 kW
(b)
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