Getting the best performance from your Indirect-Direct Evaporative Cooling (IDEC) systems

Appropriate sizing and product design come first. IDEC systems work with outside air, and their performance varies with ambient wet-bulb depression, occupancy pattern, and operating schedule. Ambient conditions in India, for example, can change significantly between seasons and even during the day. For example, a system designed for a hot, dry Ahmedabad summer will almost certainly behave differently during the humid period immediately before the monsoon. Thus, good controls are important to deliver maximum cooling and economic benefit across all conditions.

Plan the air distribution including exhaust. IDEC systems deliver cooling by moving large quantities of air while consuming relatively little power. HMX machines are designed carefully for low-loss air movement and low leakage to achieve high energy-efficiency.

To achieve this benefit in actual practise, cooled air should also reach the target zone without excessive duct losses or heat gain. Long duct runs and unnecessary bends increase both fan power and operating cost. Keep air paths as short as practical to avoid unnecessary pressure drop. In composite climates, consider how cooling will be delivered during both hot and dry and humid periods of the year.

A building receiving large quantities of outdoor air must also have an effective exhaust path. Exhausting most of the supplied air helps avoid pressure build-up, humidity accumulation, and loss of cooling effectiveness. On the other hand, certain applications may demand a slight positive pressure indoors. Equally important, the cooled supply air should not short-circuit directly to the exhaust openings without delivering its cooling effect.

Water distribution is as important as water quality. Even with acceptable make-up water, blocked distributors, poor drainage, or uneven wetting can reduce cooling performance significantly before any major mechanical issue becomes evident.

Access for maintenance to clean filters, inspect the sump, and service of the heat exchanger should be considered in the design stage. The actual maintenance requirement depends on dust levels, water quality, operating schedule (e.g. continuous versus start-stop operation), and nearby activities at the site. Based on long experience under Indian and international conditions, HMX recommends preventive maintenance at least twice each year: once before the cooling season and again after the monsoon.
The best-performing IDEC installations are rarely the result of a single design decision. They are usually the outcome of good equipment selection, excellent machinery, thoughtful layout, careful operation, and consistent maintenance throughout the life of the system.