Firefighter Nozzle Reaction

Abstract

Nozzle reaction and hose tension are analyzed using conservation of fluid momentum and assuming steady, inviscid flow and a flexible hose in frictionless contact with the ground. An expression that is independent of the bend angle is derived for the hose tension. If this tension is exceeded owing to anchor forces, the hose becomes straight. The nozzle reaction is found to equal the jet momentum flow rate, and it does not change when an elbow connects the hose to the nozzle. A forward force must be exerted by a firefighter or another anchor that matches the forward force that the jet would exert on a perpendicular wall. Three reaction expressions are derived, allowing it to be determined in terms of hose diameter, jet diameter, flow rate, and static pressure upstream of the nozzle. The nozzle reaction predictions used by the fire service are 56 -90% of those obtained here for typical firefighting hand lines. Sharing these findings with the fire protection community can improve the safety of firefighters.

Backward Reaction Force in a Firehose

“…In this letter we use some simple fluid flow examples and calculations using Newton's second law in the control volume approach, to give support to our conceptual explanation for the backward force on a firehose. We also show how our explanation in [1] differs from Chin et al results [2]. The explanation for the backward force on the firefighters given in our previous work [1] is that the force is produced in a bend behind the firefighters and it is transmitted by the hose, producing a force that is interpreted by firefighters as being produced at the nozzle.…”

“…In a previous experimental work published in this journal [1] we showed that the reaction force produced at the nozzle does not exist and that the force counteracted by firefighters exists but is a consequence of the interaction of water with the inner walls of a bent hose. In a recent paper in this journal entitled Firefighter Nozzle Reaction, Selena K. Chin, Peter B. Sunderland, and Grunde Jomaas [2], concluded that the water jet momentum ejected from a firehose is produced at the nozzle and that the backward nozzle reaction in a firehose is always equal to the jet momentum flow rate. Although this backward force on the firefighters apparently agrees in magnitude and direction with firefighting experience, it contradicts the experiment reported in our previous work [1].…”

Quantification of radiative attenuation provided by fire hose nozzles

“…In France, three standards [?, ?, ?, ?, ?, ?, ?, ?, 2,3] Despite the fact that these nozzles are common tools for firefighters, few scientific studies have been performed to assess the efficiency of these extinction devices. To the best of our knowledge, the most recent studies on fire hose nozzle mainly concern the evaluation of the "backward reaction", as treated by Vera et al [5,6], Chin et al [7] or Sun et al [8]. However, no particular literature is devoted to the thermal efficiency of hose nozzles for firefighting operations.…”