Every HVAC engineer knows that air quality usually improves with the more outside air that is brought into a space. This is particularly true for hospitals and other spaces where indoor air contamination is an issue. However, using lots of outside air means also having to use more energy to condition the air.
In many parts of the United States, outside air in the summer is warm and moist. To remove that moisture, air conditioning systems must cool the air to the desired leaving dewpoint. Often that required dewpoint temperature is lower than what is needed to remove the sensible heat in the space. So, the space will have to employ expensive reheat to keep from overcooling the space on top of the energy required to cool the air.
Researchers at Purdue University have created an alternative – just filter out some of the humidity. Using membrane designed to desalinate water, these scientists have built a system to remove some of the water vapor without cooling the air. The membranes are selectively permeable to water with a pressure difference. Air is blown across the membranes and some of the moisture passes through, leaving less humid air that bypasses the membrane. The less humid air is easier to cool and dehumidify.
Computer simulations predict significant savings in buildings like hospitals and laboratory facilities that require high volumes of outside air. Savings are also higher in areas that are warm and humid most of the year – like Houston, Tampa, Miami, and New Orleans as expected. Dehumidification is often 40% of HVAC energy system use and much of this can be eliminated with such a system. More outside air is also healthier and safer with the threat of diseases like COVID too. – Steve Terry, DTC HVAC & Refrigeration Instructor
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