Humid air

Overview

ABSTRACT

Before use the air for air-conditioning must be treated in order to meet the required specifications in terms of temperature and hygrometry. In practice, the treatment process requires a sequence of operations which mainly includes humid air reheating, humid air cooling with or without humidification, adiabatic mixture of two humid airs with different characteristics, humidification and humidification. The humid air diagram, often the Carrier diagram, illustrates these operations.

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AUTHOR

Ahmed BENSAFI: Thermal and thermodynamic expert - CETIAT (Centre d'études techniques des industries aérauliques et thermique)

INTRODUCTION

Text originally written by Maxime DUMINIL, updated by Ahmed BENSAFI

The air used to condition a room must first be treated to achieve the required temperature and humidity specifications. In practice, the treatment process requires a sequence of operations, the main ones of which are examined in this dossier:

heating humid air ;
cooling humid air with or without dehumidification ;
adiabatic mixing of two humid airs with different characteristics;
humidification ;
dehumidification.

The moist air diagram illustrates these operations. Unless otherwise indicated, the Carrier diagram is always used. The general structure of an all-season air handling system can also be deduced from it.

We assume steady-state conditions for the energy and mass balances.