Desiccant-Enhanced Hybrid Evaporative Air Pre-Cooler
Indirect Evaporative Cooling System: Desiccant Pre-Cooler with Direct Expansion Chiller vs. Direct Expansion Chiller
Combining the basic indirect evaporative cooler with a desiccant pre-stage allows for evaporative coolers to operate efficiently under higher-humidity conditions than would be normally possible.
Synopsis:
Based upon the same basic principles that allowed humans to cool their homes using evaporating water for thousands of years, evaporative coolers change sensible heat within air into latent heat contained within evaporated water. This principle has been exploited through so-called ‘Swamp Coolers’ which evaporate water directly into the stream of air which is directed into the conditioned space (called the product stream). This has certain drawbacks, however, including the possibility of increasing moisture content in the product stream to an uncomfortable level, as well a tendency to produce musty smells in the conditioned air (both contributing to the term “swamp cooler”).
More recently, coolers have been commercialized which use “indirect” evaporative cooling very effectively. While the basic cooling mechanism in these devices continues to be evaporated water into a stream of warm air, in an indirect setup this evaporation stream is kept physically separated from the product stream air going into the conditioned space. Indirect evaporative cooling technologies using the patented, and U.S. Department of Energy (US DOE) tested, Maisotsenko Cycle have been demonstrated to reduce energy consumption by up to 90% versus traditional direct expansion refrigerator air conditioners, without introducing moisture or smells to the product stream. These indirect evaporative coolers, however, are limited geographically operating most efficiently in “high and dry” climates, and somewhat less effectively in “low and dry” climates, and not effectively at all in high humidity areas.
Combining the basic indirect evaporative cooler with a desiccant pre-stage allows for evaporative coolers to operate efficiently under higher-humidity conditions than would be normally possible. This hybrid technology is being employed successfully in Japan. A desiccant/indirect evaporative cooler is often used in conjunction with facilities’ process heating, where the waste heat is used to dry the desiccant in the HVAC unit.
Energy Savings: 25%
Energy Savings Rating: Concept validated:
What's this?
| Level | Status | Description |
| 1 | Concept not validated | Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts. |
| 2 | Concept validated: | An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles. |
| 3 | Limited assessment | An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline. |
| 4 | Extensive assessment | Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions. |
| 5 | Comprehensive analysis | Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications. |
| 6 | Approved measure | Protocols for technology application are established and approved. |