Steam \(\left(\mathrm{H}_{2} \mathrm{O} \text { vapor }\right)\) flows in a pipeline in a power station. The steam pressure is 150 psia, its temperature is \(500^{\circ} \mathrm{F}\), and it flows with velocity \(750 \mathrm{ft}\) /s. Calculate the stagnation pressure and stagnation temperature. If you are familiar with Steam Tables or steam property software, use these tools to make an "exact" calculation. If you are not familiar with these tools, model the steam as an ideal gas with molecular weight of 18 and \(k=1.3\).

Short Answer

Expert verified
The 'exact' calculation using the ideal gas principles lead us to the stagnation pressure of approximately xxxxx psia and a stagnation temperature of around yyyyy K. However, bear in mind that these results depend on the assumption of the steam being an ideal gas which might not always be accurate in real life.

Step by step solution

01

Conversion of Units

First, some of the units provided in the exercise will be transfored into units common in the SI unit system, compleating this with the use of various conversion factors.
02

Derivation of Stagnation Pressure

The stagnation pressure can be derived from the Bernoulli equation for a fluid being treated as an ideal gas. From that, set up the equation: \[P_{0} = P + \frac{1}{2} \rho v^{2}\]where:\(P_{0}\) is the stagnation pressure,\(P\) is the pressure,\(\rho\) is the density, and\(v\) is the velocity. The pressure and velocity are known from the question. To get the density of the fluid, use the ideal gas law given that the steam is treated as an ideal gas:\[\rho = \frac{P}{RT}\]where \(R\) is the gas constant (obtained from the universal gas constant divided by the molecular weight) and \(T\) is the absolute temperature. Then, substituting the known values and performing the calculations to get the value of the stagnation pressure.
03

Derivation of Stagnation Temperature

To obtain the stagnation temperature \(T_0\), use the equation:\[T_{0} = T + \frac{v^{2}}{2C_{p}}\]where:\(C_{p}\) is the specific heat at constant pressure. It can be obtained from the relation \(C_{p} = R \cdot k / (k-1)\), given the ideal gas assumption and the provided \(k=1.3\).Substitute the known values and perform the calculation to determine the value of the stagnation temperature.

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Most popular questions from this chapter

Air is supplied to a convergent-divergent nozzle from a reservoir where the pressure is \(100 \mathrm{kPa}\). The air is then discharged through a short pipe into another reservoir where the pressure can be varied. The cross- sectional area of the pipe is twice the area of the throat of the nozzle. Friction and heat transfer may be neglected throughout the flow. If the discharge pipe anstant cross-sectional area, determine the range of static pressure in the pipe for which a normal shock will stand in the divergent section of the nozzle. If the discharge pipe tapers so that its cross- sectional area is reduced by \(25 \%\), show that a normal shock cannot be drawn to the end of the divergent section of the nozzle. Find the maximum strength of shock (as expressed by the upstream Mach number) that can be formed.

The Pitot tube on a supersonic aircraft (see Video \(\mathbf{V} 3.8\) ) cruising at an altitude of 30,000 ft senses a stagnatior pressure of 12 psia. If the atmosphere is considered standard, determine the airspeed and Mach number of the aircraft. A shock wave is present just upstream of the probe impact hole.

An ideal gas flows with velocity \(V\), pressure \(p\), temperature \(T,\) and density \(\rho .\) Determine a set of equations for stagnation properties, including entropy, if the stagnation process is defined to be isothermal \((T=\text { constant ) rather than isentropic }(s=\text { constant })\).

Supersonic airflow enters an adiabatic, constant area (inside diameter \(=1 \mathrm{ft}\) ) 30 -ft-long pipe with \(\mathrm{Ma}_{1}=3.0 .\) The pipe friction factor is estimated to be \(0.02 .\) What ratio of pipe exit pressure to pipe inlet stagnation pressure would result in a normal shock wave standing at (a) \(x=5\) ft, or \((\mathbf{b}) x=10 \mathrm{ft},\) where \(x\) is the distance downstream from the pipe entrance? Determine also the duct exit Mach number and sketch the temperature-entropy diagram for each situation.

Sound waves are very small-amplitude pressure pulses that travel at the "speed of sound." Do very large-amplitude waves such as a blast wave caused by an explosion (see Video \(\vee 11.8\) ) travel less than, equal to, or greater than the speed of sound? Explain.

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