Lecture

Humid Air and Water Vapor: Properties and Behavior

Graph Chat

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

In course

PHYS-118: Building physics

Ce cours traite des principaux phénomènes physiques observables dans le bâtiment et doit permettre à l'étudiant d'acquérir des connaissances de base dans le domaine de la physique du bâtiment. ...

Description

This lecture covers the properties and behavior of humid air and water vapor, including concepts such as water vapor pressure, condensation, mist formation, and relative humidity. It explains the physical quantities involved, the saturation of water vapor, and the impact on air humidity. The lecture also delves into psychrometric diagrams, dew point determination, and the process of air drying.

Instructors (2)

Jean-Louis Scartezzini

Director of EPFL Solar Energy and Building Physics Laboratory (1994-present); Founder & Director of ENAC Institute of Infrastructures, Resources and Environment (2002-2009); Founder & Director of EPFL Doctoral Program in Environment (2002-2009); Co-Director of EPFL Institute of Building Technology (1994-1997); Associate Professor of Building Physics at EPFL (1994-1997); Associate Professor of Building Physics at University of Geneva (1990-1997); Group Leader & Research Fellow at the EPFL Solar Energy Research Group (1981-1989); Research Fellow at the Applied Geophysics Institute of University of Lausanne (1980-1981).

Andreas Schueler

Studies of Physics at the University of Freiburg, Germany
Master of Science (Physics) from the University of Michigan, Ann Arbor, USA
PhD degree from the University of Basel, Switzerland

Official source

Ontological neighbourhood

Earth science

Atmospheric science: Meteorology

Related concepts (32)

Humidity

Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depends on the temperature and pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air. A related parameter is the dew point. The amount of water vapor needed to achieve saturation increases as the temperature increases.

Psychrometrics

Psychrometrics (or psychrometry, ; also called hygrometry) is the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures. Although the principles of psychrometry apply to any physical system consisting of gas-vapor mixtures, the most common system of interest is the mixture of water vapor and air, because of its application in heating, ventilation, and air-conditioning and meteorology.

Vapor pressure

Vapour pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquid's thermodynamic tendency to evaporate. It relates to the balance of particles escaping from the liquid (or solid) in equilibrium with those in a coexisting vapor phase. A substance with a high vapor pressure at normal temperatures is often referred to as volatile.

Hygrometer

A hygrometer is an instrument which measures the humidity of air or some other gas: that is, how much water vapor it contains. Humidity measurement instruments usually rely on measurements of some other quantities such as temperature, pressure, mass and mechanical or electrical changes in a substance as moisture is absorbed. By calibration and calculation, these measured quantities can lead to a measurement of humidity.

Vapour pressure of water

The vapour pressure of water is the pressure exerted by molecules of water vapor in gaseous form (whether pure or in a mixture with other gases such as air). The saturation vapour pressure is the pressure at which water vapour is in thermodynamic equilibrium with its condensed state. At pressures higher than vapour pressure, water would condense, whilst at lower pressures it would evaporate or sublimate. The saturation vapour pressure of water increases with increasing temperature and can be determined with the Clausius–Clapeyron relation.

Related lectures (60)

Ideal Gas Law and Humidity Control

Covers the ideal gas law, molar mass, absolute temperature, and humidity control concepts.

Atmospheric Phenomena and Calorimetry

Covers atmospheric phenomena, vapor pressure, humidity, and animal metabolism scaling law.

Snowfall Records and Crystal Formation

Explores snowfall records, crystal formation, atmosphere composition, vapor pressure, cloud formation, and precipitation mechanisms.

Capacitive Humidity Sensors

Explores capacitive humidity sensors, hygroscopic polymers, dew point measurement, and proximity sensors.

Thermal Comfort Fundamentals