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Lecture

Heat Transfer: Latent Heat and Enthalpy

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 concepts of latent heat and enthalpy in the context of heat transfer. It explains how the overall heat content of humid air is linked to changes of state, particularly evaporation. The instructor discusses the importance of latent heat in processes like evaporation and how it affects the heat content of moist air. The lecture also delves into the role of sensible heat and water evaporation in determining the heat content of humid air. Various factors influencing thermal comfort, such as air temperature, relative humidity, and clothing, are explored in detail, along with mechanisms like radiation, air speed, and sweat production.

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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

Mechanical engineering

Thermal engineering: Air conditioning

Related concepts (32)

Heat

In thermodynamics, heat is the thermal energy transferred between systems due to a temperature difference. In colloquial use, heat sometimes refers to thermal energy itself. An example of formal vs. informal usage may be obtained from the right-hand photo, in which the metal bar is "conducting heat" from its hot end to its cold end, but if the metal bar is considered a thermodynamic system, then the energy flowing within the metal bar is called internal energy, not heat.

Heat transfer

Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species (mass transfer in the form of advection), either cold or hot, to achieve heat transfer.

Latent heat

Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process—usually a first-order phase transition. Latent heat can be understood as hidden energy which is supplied or extracted to change the state of a substance (for example, to melt or vaporize it) without changing its temperature or pressure. This includes the latent heat of fusion (solid to liquid), the latent heat of vaporization (liquid to gas) and the latent heat of sublimation (solid to gas).

Evaporative cooler

An evaporative cooler (also known as evaporative air conditioner, swamp cooler, swamp box, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning systems, which use vapor-compression or absorption refrigeration cycles. Evaporative cooling exploits the fact that water will absorb a relatively large amount of heat in order to evaporate (that is, it has a large enthalpy of vaporization).

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.

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