The ventilation air intake (louver) is the first line of defence against an unfavourable outdoor climate. Unfortunately, the importance of this component is often an underestimated issue in the design process of many heating, ventilation and air conditioning (HVAC) systems. Field studies and inspections of a representative number of HVAC plants carried out between 1995 and 1998 in and around the city of Trondheim revealed that snow, and in several cases rain, easily passes through the air intake louver. Such intrusion of humidity can lead to unwanted microbial growth in the HVAC system.

Based on theoretical and experimental tests it was determined that the thermodynamic balancecondition in the working space of air-handling units (AHUs) of heating, ventilating and aircondltioningsystems (HVAC systems) is entirely defined by the humidity potential of thefinal parameters of air and water: @ = constant [1]. This makes it possible to put forward anew thermodynamic method for the analysis and calculation of heat and moisture exchange inAHUs of HVAC systems [2,3].

A patented, low energy, fresh air fan convector has been developed by a HVAC equipmentmanufacturer in conjunction with a leading controls supplier and a local University. It canheat, free cool, provide minimum ventilation air and carry out night cooling strategies in anintelligent self contained package. A number of full-scale tests have been carried out on theunit.

In mechanical exhaust ventilated buildings in cold climates, the supply air through vents in the perimeter may cause draught and reduce the zone of occupancy. One way to prevent this is to preheat the outdoor air by a vent-convector. An experimental study of the performance of a vent-convector is reported in this paper. Measurements have been conducted in a test room and in a school equipped with vent-convectors. Air flow and pressure drop characteristics were investigated for one type of vent-convector. the temperature variation at a step change of the air flow was also investigated.

This technical note considers the performance evaluation of an advanced air-conditioningsystem in a plant manufacturing electrical generators. The extensive field measurements ofthermal climate and indoor air quality were performed during five periods of extreme weatherconditions in 1994-1996. In order to describe the performance of the air-conditioning system,the thermal climate and indoor air quality were determined. The air-conditioning system wasable to maintain the thermal climate within the range recommended in the ISO standard 7730for most of the time.

Suitable combinations of desiccant and evaporative cooling systems permit air processes alternative to the traditional ones for air conditioning applications. But owing to the high costs of desiccant wheels, we need very strong energy savings in order to demonstrate an economy validity. These savings can be possible today by the last generation of desiccant wheels where the most part of the regeneration heat can be supplied by heat recovery from chillers.

This field study was organised to track differential pressure relationships in critical care units of a metropolitan hospital. Maintaining design pressure balances is essential to control risk of airborne disease transmission within these units. the pressure differentials that exist between two patient isolation facilities (positive and negative) and their surrounding spaces were monitored continuously for one week.

Residential ventilation systems can be categorized as supply, exhaust, or balanced systems.This effort focused on establishing a design methodology for central-fan-integrated supplyventilation systems. Air flow measurements were taken for 7.6 m lengths of 12.7 cm through22.9 cm diameter flexible ducts, with a 15.2 cm wall-cap, at duct pressures of -10 Pa to -120Pa. Using these measurements and field experience, a five-step method was developed as aguide for sizing and installing the ventilation system.

The HVAC components are usually made of galvanised sheet metal which is covered by a corrosion protection and also lubricant oils are used in machine tools in manufacturing of the components or ducts. The aim of this study was to test and develop a consistent method to determine oil concentrations on component surfaces. Two swiping methods and a filter contact method were tested. In al of them the analysis based on IR-spectrometry. The results show that oil concentration is quite high and unequally distributed on the surface of the sheet metal containing corrosion protection oil.

Different ground-coupled earth-to -air heat exchangers have been constructed in many residential and occupational buildings in Switzerland to precool or preheat the incoming air. Many technical and energetic facts favour such systems. The objective of this study was to determine if microbial growth occurs within these tubes and if adverse health effects must be considered. The results show large reductions in viable bacteria and spore concentrations along the tubes and very low concentrations in the supply air compared to the outdoor air.