Introduction to Steam Tables

LearnChemE
21 Aug 201403:15
EducationalLearning
32 Likes 10 Comments

TLDRThis screencast explores the use of steam tables, which detail properties of water in liquid and vapor states, including specific volume, enthalpy, internal energy, and entropy. The video demonstrates how to calculate the density of water at its critical point (373.95°C) and determine the quality of water at 100°C using given enthalpy values. It explains the concept of quality as the fraction of water in vapor phase and uses steam tables to find the enthalpy of liquid and vapor at saturation conditions, concluding that the water is 83% vapor and 17% liquid at this temperature.

Takeaways
  • 💧 The script discusses the use of steam tables for understanding properties of water in different states.
  • 🔍 The critical point of water is identified where liquid and vapor volumes are equal, occurring at 373.95°C.
  • 📏 The critical volume of water is provided as 0.003106 m³/kg, which is used to calculate density.
  • 📉 The density of water at the critical point is calculated as the reciprocal of its volume, resulting in approximately 323 kg/m³.
  • 🌡 The script explains how to calculate the quality of water at a given temperature, using 100°C as an example.
  • 🔥 The concept of 'quality' is defined as the fraction of water that is in the vapor phase at saturation conditions.
  • 📚 Reference is made to a thermodynamics textbook by Elliott and Lira for specific enthalpy values from steam tables.
  • ♨️ At 100°C, the enthalpy of water is given as 2300 kJ/kg, which is used to determine the quality of the water.
  • 🔄 The quality calculation involves the enthalpy of both the liquid and vapor phases at saturation conditions.
  • 📈 The script concludes that at 100°C with an enthalpy of 2300 kJ/kg, the water is 83% vapor and 17% liquid.
  • 📝 The importance of using accurate and significant figures in scientific calculations is highlighted throughout the script.
Q & A

  • What are steam tables used for?

    -Steam tables are used to provide compilations of properties for water, such as specific volume, specific enthalpy, internal energy, entropy, saturation pressures, and saturation temperatures, for both liquid and vapor phases.

  • What is the critical point of water?

    -The critical point of water is the temperature and pressure at which the liquid and vapor phases have the same volume, which is at 373.95 degrees Celsius.

  • What is the density of water at its critical point?

    -The density of water at its critical point is calculated as the reciprocal of its specific volume, which is 1 / 0.003106 m^3/kg, resulting in approximately 322.5 kg/m^3 when rounded to three significant figures.

  • What does the term 'quality' refer to in the context of thermodynamics?

    -In thermodynamics, 'quality' refers to the fraction of the total mass that is in the vapor phase in a mixture of liquid and vapor at saturation conditions.

  • What is the given enthalpy value for water at 100 degrees Celsius in the script?

    -The given enthalpy value for water at 100 degrees Celsius is 2300 kJ/kg.

  • What are saturation conditions in the context of steam tables?

    -Saturation conditions refer to the state where the liquid and vapor phases are in equilibrium at a given temperature and pressure, with the vapor phase being in contact with the liquid phase.

  • How is the quality of water calculated at a given temperature and enthalpy?

    -The quality of water is calculated using the known enthalpies of the liquid and vapor phases at saturation conditions and the enthalpy of the mixture. It involves solving for the fraction of the vapor phase using the formula that relates the mixture's enthalpy to the enthalpies of the liquid and vapor phases.

  • What is the significance of the enthalpy of liquid and vapor at saturation conditions?

    -The enthalpy values for liquid and vapor at saturation conditions are crucial for determining the quality of the mixture, as they represent the energy content of each phase and are used to calculate the overall energy state of the mixture.

  • What is the calculated quality of water at 100 degrees Celsius with an enthalpy of 2300 kJ/kg?

    -The calculated quality of water at 100 degrees Celsius with an enthalpy of 2300 kJ/kg is approximately 83% vapor, indicating that 83% of the water is in the vapor phase and 17% is in the liquid phase.

  • Where can one find the enthalpy values for liquid and vapor at saturation conditions?

    -The enthalpy values for liquid and vapor at saturation conditions can be found in steam tables, which are typically included in thermodynamics textbooks or engineering reference materials.

  • What textbook is mentioned in the script for reference to steam tables?

    -The script mentions a thermodynamics textbook by Elliott and Lira as a reference for steam tables.

Outlines
00:00
🔍 Understanding Steam Tables and Water's Critical Point

This paragraph introduces the concept of steam tables, which are essential tools in thermodynamics for determining properties of water in both liquid and vapor phases. The focus is on the critical point of water, where the densities of liquid and vapor are equal, occurring at 373.95 degrees Celsius. The critical volume is provided, and the density is calculated as its reciprocal, resulting in a value with three significant figures.

🌡 Calculating the Quality of Water at 100 Degrees Celsius

The second paragraph delves into the calculation of water's quality at 100 degrees Celsius, given its enthalpy as 2300 kJ/kg. Quality refers to the fraction of water in the vapor phase. Using steam tables from a thermodynamics textbook by Elliott and Lira, the enthalpy values for liquid and vapor at saturation conditions are identified. The paragraph explains the formula for calculating the quality of the water, which involves the enthalpy of both the liquid and vapor phases. The calculation reveals that at this temperature, the water is 83% vapor and 17% liquid.

Mindmap
Keywords
💡Steam Tables
Steam tables are a compilation of thermodynamic properties of water and steam, such as specific volume, specific enthalpy, internal energy, and entropy. They are crucial for engineers and scientists working with systems involving phase changes of water. In the script, steam tables are used to find properties like enthalpy at saturation conditions, which is essential for calculating the quality of water at a given temperature.
💡Critical Point
The critical point of a substance, such as water, is the temperature and pressure at which the liquid and gas phases coexist in equilibrium. At this point, the densities of the liquid and vapor phases are equal. In the script, the critical point of water is mentioned as 373.95 degrees Celsius, where the density is calculated using the specific volume provided.
💡Density
Density is a measure of mass per unit volume of a substance. It is an important property in thermodynamics for determining the amount of substance in a given space. In the context of the video, the density of water at its critical point is calculated by taking the reciprocal of the specific volume, which is a key step in understanding the phase behavior of water.
💡Quality of Water
In thermodynamics, the quality of water refers to the fraction of the total mass that is in the vapor phase at a given temperature and pressure. It is used to describe the state of a substance that is part liquid and part vapor. The script calculates the quality of water at 100 degrees Celsius using the given enthalpy value, which helps in understanding the phase distribution of water at this temperature.
💡Enthalpy
Enthalpy is a thermodynamic property that represents the total heat content of a system. It is often used to describe the energy changes during phase transitions. In the script, the enthalpy of water at 100 degrees Celsius is given as 2300 kJ/kg, which is used to determine the quality of the water at this temperature.
💡Saturation Conditions
Saturation conditions occur when a substance is at the point where it can exist in equilibrium between its liquid and vapor phases. At this point, the pressure and temperature are specific and correspond to the substance's saturation properties. The script refers to saturation conditions to find the enthalpy values for liquid and vapor phases of water at 100 degrees Celsius.
💡Vapor Phase
The vapor phase is one of the two primary states of matter, the other being the liquid phase. In the context of the script, the vapor phase is part of the water's state at saturation conditions, and its enthalpy is used to calculate the quality of the water.
💡Liquid Phase
The liquid phase is the state of matter where particles are close together but can move freely, allowing the substance to take the shape of its container. In the script, the liquid phase of water is considered when calculating the quality, where its enthalpy is used in conjunction with the vapor phase enthalpy.
💡Fraction
A fraction in the context of the script refers to the proportion of the total mass of water that is in either the liquid or vapor phase. The calculation of the quality of water involves determining the fraction of the water that is in the vapor phase at a given temperature.
💡Thermodynamics Textbook
A thermodynamics textbook, such as the one by Elliott and Lira mentioned in the script, is a resource that provides detailed information on the principles of thermodynamics, including properties like enthalpy and specific volume. The textbook is used as a reference to find the necessary values for the steam table calculations in the video.
💡Significant Figures
Significant figures are the digits in a number that carry meaningful information about its precision. In scientific calculations, it's important to round results to an appropriate number of significant figures to maintain accuracy. The script mentions rounding the calculated quality of water to three significant figures to ensure the result is reported with the correct level of precision.
Highlights

Introduction to steam tables as compilations of properties for water in liquid and vapor phases.

Explanation of specific volume, specific enthalpy, internal energy, and entropy listed in steam tables.

Mention of saturation pressures and temperatures included in steam tables.

Task to determine the density of water at its critical point.

Identification of the critical point as where liquid and vapor volumes are equal.

Statement of the critical point occurring at 373.95 degrees Celsius.

Calculation of density at the critical point using the formula 1 over volume.

Presentation of the density value with three significant figures.

Calculation of the quality of water at 100 degrees Celsius given an enthalpy of 2300 kJ/kg.

Definition of quality as the fraction of water in the vapor phase.

Use of saturation conditions to determine enthalpy values from steam tables.

Reference to a thermodynamics textbook by Elliott and Lira for enthalpy values.

Explanation of how to calculate the quality using the enthalpy of liquid and vapor phases.

Determination that the fraction of vapor phase is 83% at 100 degrees Celsius.

Calculation of the remaining 17% as the liquid phase fraction.

Emphasis on solving for quality with attention to significant figures.

Transcripts

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Related Tags
Steam TablesThermodynamicsDensity CalculationEnthalpyQuality of WaterSaturation ConditionsPhase EnvelopeCritical PointVapor FractionEnergy Analysis