Evaporative Cooling Pads

タイトルまたは説明

Evaporative cooling is one way to reduce temperatures inside buildings. As water evaporates, it absorbs energy from the surrounding environment. A well-maintained ventilation system with evaporative cooling can reduce incoming air *0 to *0°F. Cooler indoor temperatures can improve the environment for plants and animals, plus significantly improve working conditions for employees.The typical evaporative pad cooling system  draws outside air into the building through wet vertical pads. The major components of this system are: pad media, water supply, pump, distribution pipe, gutter, sump, and bleed-off line. As air flows past the moist pad surfaces, some of the moisture evaporates into the air stream. Heat is withdrawn from the air during this process and the air leaves the pad at a lower temperature with higher moisture content.

Water is continuously circulated over and through the pad cells during operation. A pump transports water from a sump through a filter and to a distribution pipe along the top of each pad. A gutter collects unevaporated water that drains from the bottom of each pad. Water can be recycled as long as salt or minerals do not collect noticeably on the pads.

Only part of the water flowing over the pad material is evaporated. Water temperature does not have a great effect on the cooling achieved. Recommended minimum water flow rates through vertically-mounted pads and sump capacities are listed in Table 1.

The excess water that is collected from the pad should be screened to remove pad fibers and other debris before the water is returned to the sump (Figure 3). A **-mesh inclined screen mounted below the return flow is generally effective. Install removable caps on the ends of water distribution pipes to allow for bi-monthly flushing and convenient access.

The salt and mineral concentrations of water in a pad system increase as water evaporates. If the mineral content of the water supply is high, a bleed-off system is essential to prevent mineral deposits in the pad. A continuous water bleed-off rate of 0.*5 gpm for every 1,**0 cfm (0.*2 L/min per m3/s) of airflow is recommended.