The performance of a ventilation system, particularly that which is incorporated in centralised air-conditioning system, can be evaluated in several ways. The "ventilation efficiency and ventilation effectiveness" and "air exchange efficiency" are two of the most commonly employed methods in ventilation analysis.
In order to improve the indoor air quality a change in the ventilation system is often one of the actions. The mean ventilation effectiveness or contaminant removal effectiveness is then often presented as a measure. Great care should however be taken when evaluating a system using these parameters. Measurements have shown that in displacement ventilation the mean ventilation effectiveness can fluctuate very much for the same air flow, the same cooling load, the same inlet - outlet devices and the same height of the tracer gas supply.
In France, air conditioning of offices is often required especially in areas with high noise levels and in the Mediterranean climates. Evaporative cooling systems appear able to give a cost effective solution to the growing demand for summer comfort: hence, the CSTB and Gaz de France are currently conducting a joint research on the efficiency of such systems. On the basis of a comfort criteria, this have been done by computer simulations taking into account different kinds of systems, buildings, and climatic areas.
The faults during design and installation phases are more critical with cooling systems than with normal HY AC systems: direct evaporated systems in particular require experienced engineers and mechanics. The most common fault is oversizing the systems and the design of the year-round-use system without winter conditions equipment. When the outdoor temperature is cold these systems present problems. The aim of this paper is to present the retrofitting concepts of cooling systems together with improved energy efficiency and operation of the system.
In the previous issue of this Newsletter, the THERMIE Programme was presented through an interview with Mr Sampaio Nunes, Director of Energy Technology at the EC's DG XVII. In order to illustrate the Programme, this issue's subject is focused on the presentation of actual projects: six new so-called Targeted Projects have indeed been approved for THERMIE support in the Building sector after the 1995 and 1996 calls, and are now getting up to speed.
This paper is not intended as an exhaustive account of all the available natural cooling techniques, including an interminable list of references, the advantages and disadvantages of each technique, and their field of application. Rather, it is intended to present the perspectives of future research and the topics that should be covered within the frame of a European concerted action. Thus, it will concentrate on the main obstacles and faults that we feel exist in the current research, and subsequently on the measures that should be taken to correct this.
This paper presents the state of the art on the natural cooling techniques. The development on the evaporative, radiative and earth contact cooling techniques and components is discussed. A classification of the existing systems and techniques is attempted and tbe knowledge on the more important of them is presented. Advantages and disadvantages of the classified systems are evaluated and their suitability for European climates is discussed. The luck of information as well as the existing scientific gaps on the subject are identified.
Fast development of computer technology and the greater use of it in all spheres of activity have caused the development of software support in the field of HV AC systems. Considering the fact that today time is of great value and that contemporary technical systems demand economy and rationalisation of operating costs and energy, the qualitative and user-friendly computer-aided engineering is of maximum importance.
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