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The pressure vessel of a nuclear reactor is filled with boiling water having a density of \(\rho_{w}=850 \mathrm{~kg} / \mathrm{m}^{3}\). Its volume is \(185 \mathrm{~m}^{3}\). Due to failure of a pump needed for cooling, the pressure release valve \(A\) is opened and emits steam having a density of \(\rho_{s}=35 \mathrm{~kg} / \mathrm{m}^{3}\) and an average speed of \(V=400 \mathrm{~m} / \mathrm{s} .\) If it passes through the 40-mm-diameter pipe, determine the time needed for all the water to escape. Assume that the temperature of the water and the velocity at \(A\) remain constant.

Short Answer

Expert verified
The time needed for all the water to escape is approximately 24.85 hours.

Step by step solution

01

Calculate the mass of the water

The mass \(m\) of the boiling water in the pressure vessel can be calculated using the formula: \(m=\rho_{w} \cdot V\), where \(\rho_{w}\) is the density of the water and \(V\) is the volume of the pressure vessel. Substituting \(\rho_{w}=850 \mathrm{~kg} / \mathrm{m}^{3}\) and \(V=185 \mathrm{~m}^{3}\) we get \(m=157250 \mathrm{~kg}\).
02

Calculate the cross sectional area of the pipe

The cross sectional area \(A_{p}\) of the pipe can be found using the formula: \(A_{p}= \pi \cdot (d/2)^2\), where \(d\) is the diameter of the pipe. Substituting \(d=0.04 \mathrm{~m}\) we get \(A_{p}= 0.001256 \mathrm{m}^2\).
03

Calculate the volumetric flow rate

The volumetric flow rate \(Q\) of steam can be calculated using the formula \(A_{p} \cdot v\), where \(v\) is the average speed. Therefore, on substituting \(A_{p}= 0.001256 \mathrm{~m}^2\) and \(v=400 \mathrm{~m} /s\), we get \(Q=0.5024 \mathrm{~m}^3/s\).
04

Calculate the time needed for all the water to escape

To find out the time \(t\) needed for all the water to escape, we use the formula: \(t= m/(\rho_{s} \cdot Q)\), where \(\rho_{s}\) is the density of the steam. Substituting \(m=157250 \mathrm{~kg}\), \(\rho_{s}=35 \mathrm{~kg} / \mathrm{m}^{3}\) and \(Q=0.5024 \mathrm{~m}^3/s\) we find that \(t= 89263 \mathrm{s}\), or approximately \(24.85\) hours.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Density Calculation
Density, symbolically represented as \( \rho \), plays a fundamental role in fluid mechanics by linking mass and volume in a simple equation: \( \rho = \frac{m}{V} \), where \(m\) is mass and \(V\) is volume. When solving problems in fluid dynamics, density is an essential property used to analyze and predict the behavior of solids, liquids, and gases under various conditions.

In our given problem, density calculation was utilized to determine the mass of boiling water in the pressure vessel using the formula \(m = \rho_w \cdot V\), multiplying the provided density of water, \(\rho_w = 850 \mathrm{kg/m^3}\), with the volume of the vessel, \(V = 185 \mathrm{m^3}\). This calculation is critical because it sets the stage for further computations, including the time needed for the water to transform into steam and escape through the valve.
Volumetric Flow Rate
Volumetric flow rate, denoted as \(Q\), is a core concept in fluid mechanics, measuring how much volume of fluid flows per unit time through a cross-section. In practical terms, it's like measuring how much water flows through a pipe every second. The formula is \(Q = A_p \cdot v\), where \(A_p\) is the cross-sectional area and \(v\) is the velocity of the fluid.

In our exercise, the volumetric flow rate calculation was critical to understand how quickly the steam escapes the pressure vessel. By using the pipe's cross-sectional area and the steam velocity, we could calculate \(Q\), which is later used to determine the total time for the water to escape. In real-world applications, this helps engineers design efficient systems to manage fluid flow, whether in industrial piping, rivers, or blood vessels in the human body.
Pressure Vessel Analysis
Pressure vessel analysis involves examining the factors that affect the performance and safety of a container holding fluids under pressure. In such analysis, engineers evaluate the structural integrity, the operating conditions, such as temperature and pressure, fluid properties, and how they interact.

In this case study, our pressure vessel lost a cooling pump, triggering the opening of the pressure release valve. The mass of escaping steam over time, based on its lower density, drives the calculation of time needed for the total mass of water to be emitted as steam. This real-world application demonstrates the critical nature of understanding pressure vessel dynamics to avoid catastrophic failures in systems like nuclear reactors, where precision and safety are paramount.

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Most popular questions from this chapter

The flat strip is sprayed with paint using the six nozzles, each having a diameter of \(2 \mathrm{~mm}\). They are attached to the 20-mm-diameter pipe. The strip is \(50 \mathrm{~mm}\) wide, and the paint is to be \(1 \mathrm{~mm}\) thick. If the average speed of the paint through the pipe is \(1.5 \mathrm{~m} / \mathrm{s}\), determine the required speed \(V\) of the strip as it passes under the nozzles.

The average velocities of water flowing steadily through the nozzle are indicated. If the nozzle is connected onto the end of the hose, outline the control volume to be the entire nozzle and the water inside it. Also, select another control volume to be just the water inside the nozzle. In each case, indicate the open control surfaces, and show the positive direction of their areas. Specify the direction of the velocities through these surfaces. Identify the local and convective changes that occur. Assume water to be incompressible.

The 2 -m-diameter cylindrical emulsion tank is being filled at \(A\) with cyclohexanol at an average rate of \(V_{A}=4 \mathrm{~m} / \mathrm{s}\) and at \(B\) with thiophene at an average rate of \(V_{B}=2 \mathrm{~m} / \mathrm{s}\). Determine the rate at which the depth of the mixture is increasing when \(h=1 \mathrm{~m} .\) Also, what is the average density of the mixture? Take \(\rho_{c y}=779 \mathrm{~kg} / \mathrm{m}^{3},\) and \(\rho_{t}=1051 \mathrm{~kg} / \mathrm{m}^{3}\)

The velocity profile for a fluid within the circular pipe for fully developed turbulent flow is modeled using Prandtl's one-seventh power law \(u=U(y / R)^{1 / 7} .\) Determine the average velocity for this case.

A viscous liquid is flowing through a channel. The velocity profile is given as \(u=2\left(e^{0.3 y}-1\right) \mathrm{m} / \mathrm{s}\), where \(y\) is in meters. If the channel is \(1.5 \mathrm{~m}\) wide, find the volumetric discharge from the channel.

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