Research Update: Natural-draft Testing on Air-cooled Heat Exchangers

To ensure reliable data collection, HTRI always seeks to improve test methods and incorporate innovative techniques. Recently installed at the Research & Technology Center, the Air-cooled Unit (ACU) has motivated us to develop better ways of collecting airside measurements for both forced- and natural-draft testing. Accurate measurements for natural-draft (fans off) testing can be especially challenging due to the relatively low airside flow rates.

Determining the precise type and quantity of instruments required for airside natural-draft testing has taken some time. HTRI has investigated various methods of measuring temperature, pressure, and flow rates, including the use of some unique gauges and probes like the hot-wire anemometer and Kiel probe. Understanding the way these instruments work and their limitations help engineers improve measurement quality.

Innovative methods like high-speed camera imaging and smoke testing on the ACU help us visualize and quantify heat plumes that would otherwise be invisible. An industrial “box” chimney with integrated instrument systems has also allowed us to investigate the effects of chimneys on natural-draft flow.

HTRI continues to enhance data collection for natural draft in the ACU. We look forward to eventually analyzing natural draft in alternate flow configurations, including hot-air recirculation, maldistribution, and induced draft configurations.