Steady-flow process

Energy Equations for Steady-State, Steady-Flow Processes... 

Fig. 4. Schematic diagram of a simple steady-flow process. See text.

Real irreversible processes can be subjected to thermodynamic analysis. The goal is to calciilate the efficiency of energy use or production and to show how energy loss is apportioned among the steps of a process. The treatment here is limited to steady-state, steady-flow processes, because of their predominance in chemical technology. 

The energy balance for a steady-state steady-flow process resulting from the first law of thermodynamics is... 

ANALYSIS OF STEADY-STATE, STEADY-FLOW PROCESSES... 

Equation 2.41 is the general energy equation for a steady flow process. 

Consider next the case where heat [GrevIx = Jx Grev is rejected (i.e. transferred from the control volume CV at temperature 7) in a reversible steady-flow process between states X and Y, in the presence of an environment at Tq- [CrevIx is taken as positive. 

A total energy balance is useful for describing the temperature changes within the flowing gas. For this open steady flow process the total energy balance is given by... 

C3H8 is burned with 10 times the stoichiometric air in a steady flow process. The reaction is complete, forming C02 and H20. The fuel and air are mixed at 400 °C before entering the combustor. The combustor is adiabatic. Specific heats are all constant, cp = 1 J/g. 

The irreversibility accompanying a steady flow process may be computed for any zone by noting the fluxes of entropy into and out of the zone. Leaving aside the problems posed by semi-permeable membranes, which introduce ambiguities into the meanings of heat and work, (2), equation (3) provides such a balance ... 

Solution This is a steady-flow process for which Eq. (2.10h) applies. The initial and final velocities of water in the storage tanks are negligible, and the term bu2/2gc may be omitted. The remaining terms are expressed in units of (Btu)(lbnl) 1 through use of appropriate conversion factors. At 200(°F) the density of water is 60.1 (lbm)(ft)-3, and l(ft)3 is equivalent to 7.48(gal) thus the mass flow rate is... 

Consider the flow-calorimeter method for measurement of heats of combustion of fuel gases. The fuel is mixed with air at room temperature and ignited. Combustion takes place in a chamber surrounded by a cooling jacket through which water flows. In addition there is a long water-jacketed section in which the products of combustion are cooled to the temperature of the reactants. Whatever the details of this steady-flow process, the overall energy balance [Eq. (2.10)] reduces to... 

If 10 mol of ethylene is heated from 200 to 1,000°C in a steady-flow process at approximately atmospheric pressure, lyhat is its entropy change ... 

Estimate the final temperature and the work required when 1 mol of 1,3-butadiene is compress isentropically in a steady-flow process from 1 bar and 60°C to 7 bar. 

What is the ideal work for the separation of an equimolar mixture of methane and ethane 150°C and 5 bar in a steady-flow process into product streams of the pure gases at 35°C and 1 if T0 = 300 K ... 

This expression of the first law for a steady-flow process is analogous to Eq. (2.4) for a nonflow process. Here, however, the enthalpy rather than the internal energy is the thermodynamic property of importance. 

Consider a steady-flow process in which the following gas-phase reaction takes place CO + i02- COj. The surroundings are at 300 K. 

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