Energy conservation for operation theatres by secondary return air system

The traditional ways of maintaining cleanliness, temperature and moisture level in anoperation theatre (OT) usually use larger HVAC system and keep both the heating andcooling functions operating at the same time. The temperature and moisture level are thusunder control at the cost of tremendous amount of wasted energy. Incorporating the HVACsystem with the newly developed secondary return air system, the system capacity can bereduced while the energy efficiency can be increased. In this paper, concepts of the secondaryreturn air system are described.

The role of the consulting engineer.

Characterisation of garage-air recirculation in a new building using a tracer.

Air recirculation in the new office and laboratory building of the Norwegian Institute for AirResearch was discovered and characterised from a leaking sulphur hexafluoride cylinderstored in the garage. The garage/staging area was located at the far end of the right wing ofthe three-storey building, and was used for loading/unloading of equipment and for storage ofequipment and compressed gas cylinders. Sulphur hexafluoride tracer was detected in thecorridor on the ground floor right wing leading to the central reception area.

The effect of recirculation on air-change effectiveness.

The effect of recirculation on the age of air is described. A new effectiveness measure called the relative air-change effectiveness is defined in such a way that the air distribution pattern in a room may be quantitatively characterized even when the age of the supply air is non-zero. This admits the evaluation of air distribution patterns in single-zone systems that recirculate air, and also multizone systems with or without recirculation.

The potential for residential demand controlled ventilation.

A literature search was performed to gain as much knowledge as was available on ventilation, indoor air quality sensors and demand controlled ventilation (DCV) strategies. Field data was gathered on the time and spatial variation of indoor air quality in houses. Appropriate designs were then developed. Design strategies are discussed elsewhere (1). Hour by hour simulations of the performance of several ventilation systems in various Canadian climates were done. Energy savings were then estimated for DCV and heat recovery ventilation with air to air heatexchange.