Ventilation : A win, win Combination
Ventilation is the process by which fresh air is introduced and stale air is removed from an occupied space to improve air quality. During the past 20 years, demands on industrial ventilation have increased with legislation, in the field of occupational safety and air quality, becoming stricter. When combined with evaporative cooling, industrial spaces have a year-round system that balances ventilation with natural cooling.
In April 2006 two new sections of commercial and industrial building regulations came into effect. All designs of new buildings put forward for building control approval must now comply with the new regulations to ensure that Building Control approval is forthcoming. The two documents are, ‘F1: Means of ventilation’ (F1) and ‘L2: Conservation of fuel and power in buildings other than dwellings’ (L2). F1 relates to the requirements for the provision of adequate ventilation in buildings to minimise condensation and maintain a healthy internal environment for occupants, while L2 relates to energy conservation and is concerned with ensuring that buildings are designed to meet the minimum standards of thermal insulation and minimise heat losses due to air leakage through the building structure.
Maintaining comfort and health are two key reasons for providing ventilation in buildings. To achieve these objectives, a ventilation system should be able to meet the following criteria:
• Provide a sufficient supply of air/oxygen for workers.
• Provide a sufficient supply of air/oxygen for industrial and other processes.
• Remove the products of respiration and bodily odour.
• Remove contaminants of harmful chemicals generated by processes.
• Remove heat generated by people, lighting and equipment inside the occupied space.
• Create air movement which is essential for feelings of freshness and comfort.
Industrial ventilation is particularly demanding because it must provide an environment in which both the work force and the product is free from harmful contaminants. It is not sufficient just to ensure an acceptable average freshness of atmosphere throughout the area; ventilation must also take into consideration the number of air changes required. Mechanical ventilation permits positive movement of desired air distribution patterns and a more uniform control of the environment within an area.
When minimum ventilation rates (air change rates) are set as part of building regulations they do not account for the local climatic conditions. Evaporative Cooling systems do not just ventilate but they cool at the same time. They are specifically designed for each application on the basis of the local climatic conditions. Often this requires a higher air change rate than the minimum specified. The effect of this higher airflow is not only to greatly improve the air quality but also to provide much needed temperature reduction in hot weather.
Whilst many companies are aware of the need for ventilation to improve air quality, they are unaware that evaporative cooling combines cooling and ventilation in one versatile appliance. For just an additional 20% more than the cost of a standard ventilating system, industrial and commercial companies are able to install an evaporative air-cooling system, which will improve working conditions thereby helping to increase production, decrease downtime and improve workers’ morale.
Evaporative air-cooling systems, such as Breezair, have wall-mounted climate control panels with control modes. In Auto mode they monitor the temperature and personal comfort setting, automatically increasing or decreasing the fan speed to maintain comfort. The fan speed can be varied manually in Manual mode and the system can be programmed in Timer mode to be switched on and off within a 24 hour period. The cool/vent mode gives the simple choice of operating the system as a cooler or ventilator as required. Within industrial environments this means that winter ventilation can still be used to remove vapours, odours and/or heat.
The very nature of evaporative cooling lends itself to environmentally friendly, energy efficient operation. Unlike a refrigeration system or heat pump, energy consumption is very low, because the cooling effect is the result of sensible heat being transferred to latent heat through the evaporation of water. Evaporative cooling energy consumption is primarily for operation of the fan. Evaporatively cooling a typical building will require approximately a quarter of the energy consumed by an equivalent refrigeration system. Furthermore, no ozone depleting chemicals are used.
Harnessing the natural evaporative process is where the real science lies behind the successful commercialisation of evaporative cooling and ventilating. Direct evaporative air coolers with a saturation efficiency of at least 80% can easily cool buildings from about 5ºC to 12ºC below the outdoor air temperature, depending on the climatic conditions. Refrigerated air conditioning can achieve the same but is unable to provide a through-flow of healthy fresh air and ventilation and will cost substantially more to install and run.
Evaporative cooling can provide excellent cooling and ventilation with minimal energy consumption using water as a working fluid and avoiding the use of ozone-destroying chlorofluorocarbons (CFCs) as used by compressor type systems. It not only improves the working environment by removing contaminants but also provides a cost effective cooling system for commercial buildings, factories and warehouses – a win, win situation.