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HVAC and Evaporative Cooling: Is there a Difference?

Heating, ventilation and air conditioning, or HVAC, systems are the traditional solution for providing thermal comfort and acceptable indoor air quality. When it comes to cooling, the conventional air conditioning components of HVAC systems transfer heat from inside a facility to the outside via a refrigerant in its coils. The process includes an evaporator, compressor, and condenser, all of which require significant power to operate and can be expensive to maintain. On average, 35% of a commercial facility’s energy use goes toward heating, ventilation, and air conditioning.

In contrast, evaporative cooling uses the latent heat of evaporation to lower the temperature and increase the air’s humidity by changing liquid water to water vapor. Because evaporative cooling is a natural process, no refrigerants are used in the cooling system. Instead, a pump pushes water over a system of cooling media, where evaporation takes place. There is minimal machinery, so warm, dry air is transformed into cool, moist air with far less energy use than traditional air conditioning. It also improves the quality of the fresh air makeup for occupants.

Many commercial and industrial settings already require a tremendous amount of power to operate. Add to that the energy consumption that comes from traditional air conditioning systems, and it can be easy to see how reducing energy usage through the implementation of evaporative cooling is attractive. Evaporative cooling can reduce energy use by up to 70% compared to compressor-based cooling systems while improving indoor air quality and reducing peak demand for cooling.

Yet, different buildings have different cooling needs. An auditorium, for example, only needs to be cooled when it is in use but, when occupied, also requires a substantial amount of fresh air. A grocery store, in contrast, needs to maintain a comfortable temperature for customers and staff members 24/7. Manufacturing facilities and data centers come with their own sets of unique demands. The heat load of equipment and the environmental conditions required for industrial processes create specific temperature and air quality parameters. The automotive industry, for example, needs to maintain a specific set of requirements in facilities where vehicles are painted to ensure that small aerosols of paint hit the surface at precisely the proper condition to spread correctly on the surface.

There are three primary types of evaporative cooling systems for industrial settings: direct, indirect and hybrid. Each provides a unique benefit to cooling in a cost-effective and environmentally friendly way that uses the least amount of natural resources possible.

Direct Evaporative Cooling Systems

Direct evaporative cooling systems reduce the air temperature using a process that evaporates water and increases the air’s moisture content. As a result, direct systems are ideally suited for use in hot, dry climates. They are especially effective in environments that have sizeable heat-load removal needs, as well as for fresh air make up systems.

 Indirect Evaporative Cooling Systems

There are many methods that provide indirect evaporative cooling. Broadly speaking, indirect evaporative cooling systems separate the moisture used for cooling from the airstream. Hot outside air is run through a heat exchanger, which reduces the enthalpy, or heat value, of the air. This process cools the air without adding moisture. In some systems, air passes through a series of tubes that are wet on the outer surface. Air is then blown over the outside of the tubes, cooling the outside air without adding moisture to the air being pumped into your building. Indirect systems are very effective in medium to large industrial settings.

Hybrid Evaporative Cooling Systems

Hybrid systems pair indirect cooling with a secondary direct cooling stage. The indirect stage will cool your air without increasing humidity, therefore reducing the energy, or enthalpy value, in the 1st stage, which lowers the wet-bulb temperature. This cooler air is then cooled a second time with the direct process to cool adiabatically along the lower wet-bulb line, to a much lower temperature than the starting wet-bulb temperature. This two-staged process, often called indirect-direct cooling, is highly effective in arid and semi-arid climates.

Portacool designs bespoke cooling material for the HVAC industry, creating customized solutions for virtually any environment. Indeed, Portacool’s evaporative cooling systems are used successfully around the world in practically every industry vertical. From hospital operating rooms to libraries with rare book collections, the humidity control available with the company’s Kuul® technology means no facility is off-limits. Contact our Customer Service team at kuulsupport@portacool.com or (800) 695-2942 for more information on how to utilize evaporative cooling in the HVAC industry.