Investigation of Turbulators for Fire Tube Boilers

Abstract

This paper summarizes an experimental study of three popular “turbulator” inserts for fire tube boilers. An electrically heated flow facility was developed to deliver hot air to a water-cooled steel tube instrumented to derive sectional average heat transfer coefficients for four regions of the tube. Reference data for the empty tube are in excellent agreement with the accepted correlation. Two commercial turbulators, consisting of narrow, thin metal strips bent and twisted in zig-zag fashion to allow periodic contact with the tube wall, displayed 135 and 175 percent increases in heat transfer coefficient at a Reynolds number of 10,000. A third commercial turbulator, consisting of a twisted strip with width slightly less than tube diameter, provided a 65 percent increase in heat transfer coefficient. The friction factor increases accompanying these heat transfer coefficient increases were 1110, 1000, and 160 percent, respectively, for the same Reynolds number. These data should be useful in assessing overall performance gains to be expected when turbulators are used in actual boilers.

Experimental study on the effect of heat transfer enhancement devices in flat-plate solar collectors

“…For a fully developed laminar flow, they found that the Nusselt number is nine times larger than that of a tube without turbulators under similar heating conditions. Junkhan et al [5] experimentally studied the effect of different turbulators installed at the tube inlet of a fire tube boiler, and observed considerable increase in heat transferred to water. Yildiz et al [6] studied the effect of a twisted strip profile used as the turbulator inside a concentric double-pipe heat exchanger.…”

Heat transfer and turbulent flow friction in a circular tube fitted with conical-nozzle turbulators

“…The strength of reverse flow and the reattached position are the main interest in many heat transfer applications such as heat exchangers, combustion chambers, gas turbine blades, and electronic devices. Junkhan et al [1] reported the heat transfer with several types of turbulators located in a tube to provide energy savings. Promvonge and Eiamsa-ard [2] experimentally studied the effects of the conical turbulator combined with the snail entrance on heat transfer rate and flow friction in a heat exchanger.…”

Thermal characterization of turbulent tube flows over diamond-shaped elements in tandem

“…Heat transfer enhancement using several types of the turbulence promoters mounted in a tube has been extensively studied for the past decades [1]. Ayhan et al [2] carried out experimental and numerical works to study the heat transfer in a tube fitted with truncated hollow cone turbulators.…”