7/30/2019 Physics in Fire Fighting- Chemical Engineering

1/1

12/23/12

Introduction

In fire fighting operation, nozzle is often used byfire fighters to control the water that spurt from thehose. A nozzle is a tube that varies in their crosssectional area thus allowing fire fighters to modify theflow rate, speed, direction and pressure of the stream.The purpose of the nozzle is to increase the kineticenergy of the flowing medium at the expense of itspressure energy and internal energy. Nozzles can bedescribed as convergent or divergent. The nozzle thatusually used by fire fighter is convergent nozzles. Thenozzle is joined to water hose and the pressure of thewater is exerted from a pump.

Figure 2: Automatic nozzle & plain nozzle

Figure 1: A pump located in fire engine Figure 3: The hose joined to the nozzle

The function of the pump is to provide pressure onthe flowing fluid. The pump that used by fire fighter can be divided into 2 types. The first one is stationarypump (Figure 1) which is located at the back of the fireengine which powered by the car engine through

power take over (fire fighter will switch the car engineto power the pump from a control panel located at thedrivers seat Figure 4). The other type of pump isportable pump which can be easily carried or move toany place which subject to space constraints.

It is important for a fire fighter to know the frictionaleffects that caused by:- Length of the hose - frictional effects are usually more

significant in the longer hose. Cross sectional area of the hose Bigger cross

sectional area of the hose will have less frictional effect. Velocity of the fluid - Frictional effects increase when the

velocity of the fluid increases. Roughness of the hose surface - Frictional effects are

significant in a rough hose. Static lift - Elevation difference between the pump outlet

and the laterals. Pressure of the pump - A higher pressure from the pump

will cause significant frictional effects.

Table 1: Size of nozzle for volumetric flow rate at optimum pressure.

ConclusionThe impulse force are subjected to the diameter of

nozzle and pressure of water. Therefore, it is important for fire fighters to know the measurement in fire fighting inorder to carry out their task efficiently.

References:-1. Kejuruteraan Bomba, Jabatan Bomba dan Penyelamat Malaysia, Siri Asas Kebombaan 7, Utusan

Publication 1997.2. Laman Web Rasm i Jabatan Bomba dan Penyelamat Malaysia, Kejuruteraan, Retrieved 2008-3-27

http://www.bomba.gov.my

Size of Nozzle (mm) Optimum pressure (bar) Volumetric flow rate (L/min)12.5 2.5 16015 3.5 28020 5 60025 7 1100

Calculation of Impulse

ECH 3103Prepared by:-

1. Gan Zhi Jie

(143377)2. Tay

Say Koon

(138067)

Newtons Third Law

Physics In Fire Fighting

= 105 = 105 1000 9.81 =0.0981

= 10.19

Mathemat ica l ly,= - 1 D ischarge ,= Velocity =

601000 4 (

1000)2

= 21.22

F rom Bernoul liEqua t ion ,Discharge ,= 2 - 2 Velocity = 29.8110.19 = 200 = 14.14 Note:g = Gravity accelerat ion (9.81kg/m2)

= Density of water (1000kg/m3

)A = Area of nozzle (m2)d = Diameter of nozzle (mm)h = Height of w ater (m)

=2

21.2

=14.14 2

21.21

= 23

2 - 3

=23 2

160 - 4

= 190

2 - Impulse can def ine as chamo m e n tu m o f a n o b j e c t.

= = 1

902 14.14

=0.157 2 - 5

P = Pressure of water (bar)

v = Velocity of w ater at no zzle exit (mL = Volumetric flow rate(L/min)

= Volumetric flow rate (m3/ s)