3.1 Ventilation modes with typical airflow patterns and air
change efficiencies 41
3.2 Typical probability density curves for the age of the air 41
3.3 Typical probability curves for the age of the air 42
3.4 Record of tracer gas concentration in the exhaust duct during
the measurement of the age of air 44
3.5 Probability functions of the age of air, calculated from the
recorded concentration illustrated in Figure 3.4 44
3.6 Arrangement of the conference room and of its surroundings 48
3.7 Arrangement of the conference room after improvement 49
3.8 Room ventilation characteristics before and after improvement 49
3.9 Minimum design for a 2-D quadratic model 55
3.10 Experimental designs C3 (left) and composite centred (right) 56
3.11 Map of the age of the air at head level 57
4.1 Measured part of outdo or air that is not supplied by the system in
mechanically ventilated buildings, shown with uncertainty band 59
4.2 Airflow rates and pressure differences as measured in a real test,
together with power law and quadratic fits 61
4.3 Principle of the guarded zone technique applied to several
walls of a room 63
4.4 Logarithmic plot of airflow rates and pressure differences 65
4.5 Schematic of building airtightness test 68
4.6 Roof corner from inside 69
4.7 Roof corner under depressurization 70
4.8 Principle of the neutral height method for assessing leakage area 73
4.9 Location of tracer injection and sampling tubes for the
measurement of leakage airflow rates in a ventilation system 75
4.10 Two measurements providing, by difference, the duct leakage to
outside of the conditioned space 76
5.1 Psychrometric chart with constant relative humidity curves and
constant enthalpy lines 80
5.2 Paths in the psychrometric chart for heating and humidifying
outdoor air in winter to reach 208C and 50 per cent relative
humidity 81
5.3 Paths in the psychrometric chart for heating outdoor air in
winter or cooling it in summer to reach 208C and 50 per cen t
relative humidity 82
5.4 Close view of a flat plate heat exchanger 84
5.5 Top half of a rotating heat exchanger 85
5.6 Relative position of fans and rotating heat exchangers 86
5.7 Schematics of an air handling unit, showing location of pressure
taps for pressure differential measurements 88
5.8 The simplified network representing the air handling unit and
ducts 89
5.9 Relative decrease of global heat recovery efficiency as a function
of exfiltration ratio
exf
and internal recirculation rate R
xs
93
viii Ventilation and Airflow in Buildings
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