Environmental Engineering Reference
In-Depth Information
to the object surface, thus effecting a change in material regain or even
condensation. This, combined with the hygroscopic or salty dust often found
on objects recovered from excavations, can be destructive.
7.3.5.7 Sound and Vibration
Air-conditioning equipment should be treated with sound and vibration
isolation to ensure quiet comfort for visitors and staff as per the ASHRAE
standards and local environmental laws.
7.3.6 Evaluation Indices
7.3.6.1 Introduction
The evaluation indices of the comfort, air quality and energy utilisation effi-
ciency can be divided into two main categories—empirical indices based on
experimental techniques and numerical indices based on numerical tech-
niques. The most common indices provide the required evaluation of the air
characteristics at individual positions (or in other scope, at individual points)
in the indoor environment.
7.3.6.2 Problem Identification
Until now, the evaluation of the comfort, air quality and energy utilisation
efficiency was performed only at individual positions (local evaluation).
There still is no general global evaluation index for several characteristics
such as the airflow movement and the contaminant concentration and its
influence on the occupancy health. Actually, the air flow distribution pattern
plays the role of the global evaluation index up today. On the other hand,
there is no global evaluation index capable of evaluating comfort, air quality
and energy utilisation efficiency simultaneously. Actually, this global index
will aid the HVAC designers in achieving the optimum design according to
the optimum indoor air quality levels [27-29].
7.3.6.3 Status Quo
Energy efficiency is better characterised in buildings through the energy
efficiency ratio (EER), an index that is mandatory in all air-conditioning and
refrigeration systems. The EER is defined as the useful output divided by the
energy input, a form of coefficient of performance. International standards
dictate that EER is greater than a pre-set value in an energy label (as shown
here in Figure 7.10) [33]. It is classified in efficiency categories from A to G,
giving the cooling output at full load in kW and the EER in cooling mode at
full load.
Countries set their own energy labels based on local industry and on
energy generation potentials and strategies. The minimum EER in Egypt,
for example, is 2.65 for split air conditioners [33]. The minimum efficiencies
