Air quality is very important for people who suffer from asthma or are allergic to dust, but it’s also equally important for the general public. Poor air quality has been linked to many heath problems including headache, fatigue, difficulty in sleeping and even cancer. Meanwhile, if you maintain good air quality in your home, it will help everyone in your family stay energized and healthy.
Families with pets need to be especially conscious of indoor air quality. That’s because pet hair contributes to air quality issues, but the main reason is that animals are at least as sensitive to air quality issues as humans are. Poor air quality has been linked to a host of health problems in cats, dogs and birds – so if your family includes a furry or feathered member, you have more incentive to invest in an IAQ system.
An improvement in Indoor Air Quality (IAQ) to acceptable levels can be quite expensive and uneconomical. In rare instances, structures are demolished rather than repaired or remediated because of poor IAQ. Potential savings from changes in building factors, that produced approximately 10 to 30% reduction in symptoms and associated costs, projected a handsome annual savings, in addition to reducing the psychosocial and societal costs.
Approaches to improve quality of health
Three general approaches for reducing allergy and asthma by changes in buildings are currently recognized: (1) control the indoor sources of the allergens and chemical compounds that cause symptoms or initial sensitization, (2) use cleaning systems to decrease the indoor concentrations of the relevant pollutants, and (3) modify buildings and IAQ in a manner that reduces viral respiratory infections among occupants.
The payback period associated with a desirable indoor environmental quality is probably very short. It is indicated that the many benefits listed would be recognized year after year, whereas the costs associated with providing the desirable indoor environmental quality are a one-time expense with minimal maintenance costs.
The expected benefits – which include reductions in absenteeism and health care costs, positive impacts on productivity, alertness, drowsiness, allergies, and illness, avoidance of property damage and remediation, and reduced maintenance costs – quickly exceeded the initial expenses associated with an improved indoor environment by use of desiccant assisted dehumidification and cooling systems.
Benefit of adapting desiccant-based dehumidification technology
An HVAC system is essential to modern life and can provide healthy and comfortable indoor environments – when properly installed, operated, and maintained. We categorized the primary factors leading to building-related illness, and found that IAQ evaluations conducted were associated with inadequate ventilation. Additionally, conventional HVAC systems cannot adequately dehumidify air in warm and humid climates – and it is not economically feasible to use only materials that are not susceptible to moisture damage.
A systemic relationship between the HVAC system, outdoor air, and indoor environment exists when indoor relative humidity is exceptionally high. A properly designed, functioning, and operating HVAC system can have a significant positive impact on reducing the number of SBS symptoms experienced within buildings.
The application of a control strategy that aids in removing organic materials and microorganisms from the air, while introducing fresh air into a building, can improve the IAQ of a building and eliminate many problems associated with ventilation and lack of fresh air in buildings.
The HVAC engineers suggested that IAQ improves when using active humidity control and continuous ventilation in indoor spaces. The built environment having desiccant systems were delivering as much as three times more outside air, while maintaining equal or better control of the indoor relative humidity than the conventional systems. The average Total Volatile Organic Compound (TVOC) concentrations tended to be lower in indoor spaces having desiccant-based systems.
It’s proved that adapting desiccant-based dehumidification technology for use in HVAC systems allows for effective moisture control and removal of IAQ-related organisms from the air stream, and offers a viable control strategy for preventing moisture damage and mold growth in buildings. Furthermore, utilization of active desiccant desiccation in humid climates results in energy savings from a reduction in latent cooling and an increase in sensible cooling, offsetting initial purchase costs while providing an economic benefit.
IAQ improvement approach of desiccant dehumidification and cooling
The desiccant wheel was constantly slow rotating (20 RPH) and adsorbing moisture (state 2) from the moist air stream on the process side (state 1), while moisture was removed from the wheel on the regeneration side exhausted to open outdoor atmosphere as shown in Fig. 1. This provided a constant adsorption medium with no phase change. Heat is necessary to release the moisture from the desiccant wheel, which results in heating of the airstream and an energy penalty.
However, the use of active desiccation saves energy costs by: 1) providing an enhanced occupant comfort (state 6) at a lower cost, 2) improved humidity control resulting in sensible versus latent cooling, 3) equipment expenditures by allowing the downsizing of the sensible cooling coil (state 5) for comparable design loads, 4) allowing independent temperature and humidity controls, and 5) allowing higher temperature set points.
The rotating honeycomb wheel is a finely divided desiccant impregnated into a matrix structure, maximizing the surface area of the desiccant material. The appearance of the honeycomb wheel resembles corrugated cardboard that has been rolled up into the shape of a wheel. The air passes through the flutes formed by the corrugations, and the wheel rotates through the process and reactivation airstreams. The flutes served as individual desiccant-lined air ducts, which maximizes the surface area of the desiccant presented to the air stream.
The rotating honeycomb wheel design has several advantages. The structure is lightweight and very porous. Different types of desiccants can be arranged into a honeycomb wheel configuration for different applications. The design allowed for laminar flow within the individual flutes, reducing air pressure resistance compared to packed beds. This allowed the honeycomb wheel to operate efficiently for low dew point and high capacity applications. The honeycomb wheels are very light, and their rotating mass is very low compared to their high moisture removal capacity.
Conclusion
It is seen that the desiccant dehumidification and cooling was effective in removing statistically significant concentrations of IAQ-related microorganisms from the air it supplies to a building. In addition, the capabilities of the desiccant wheel at removing airborne concentrations of IAQ-related microorganisms were explored.
The purpose of exploring the removal capabilities at different desiccant regeneration temperature was to establish the mechanism of significant removal of airborne contaminants with greater efficiencies by use of different methods. The ability of active desiccants to remove particulates, bio-aerosols, chemical pollutants, and water vapour from the airstream delivered to a building provides a unique opportunity to view active desiccant technology as a viable control strategy for enhancing and maintaining a favourable IAQ in cooling different climates. The future is for desiccant air conditioner – because it can improve indoor air quality and reduce energy consumption since the cost of energy is ever increasing.
Dr. (Prof.) D.B. Jani received Ph.D. in Thermal Science (Mechanical Engineering) from Indian Institute of Technology (IIT) Roorkee. Currently he is a recognized Ph.D. Supervisor at Gujarat Technological University (GTU). He has published more than 180 Research Articles in reputed International Conferences and Journals. He has also published 5 reputed books in the area of thermal engineering. Presently, he is an Associate Professor at GEC, Dahod, Gujarat Technological University, GTU, Ahmedabad (Education Department, State of
Gujarat, India). His area of research is Desiccant cooling, ANN, TRNSYS, and Exergy.
