WO2019239421A1

WO2019239421A1 - Split exhaust system with single and multiple suction fans for flue gases in a kitchen chimney

Info

Publication number: WO2019239421A1
Application number: PCT/IN2018/050523
Authority: WO
Inventors: Harvinder Singh Saini
Original assignee: Bongarala Vijaya Kumar
Priority date: 2018-06-16
Filing date: 2018-08-11
Publication date: 2019-12-19

Abstract

A Chimney intended for expulsion of kitchen exhaust gases with plurality of suction fans is provided. Multiple suction fans of the Kitchen chimney increase the rate of discharge of hot gases and vapours in large cross sectional ducts and provide a higher suction power and for vent the solid waste from exhaust fan. The improved Kitchen chimney provides a noise free environment, with optimally reduced decibel effects, which is easy for maintenance with Optimally reduced vibration and Optimally improved exhaust. The fans of the Kitchen chimney, are arranged in any direction ( horizontal, Vertical and cross ) and the number of fans depends on the cross sectional area of the duct pipe wherein there need not be any restriction on chimney size but size of exhaust fan is restricted. The chimney with suction fans, orient the vapours in streamlined manner to one direction and also reduces in noise and vibrations.

Description

SPLIT EXHAUST SYSTEM WITH SINGLE AND MULTIPLE SUCTION FANS FOR

FLUE GASES IN A KITCHEN CHIMNEY

FIELD OF INVENTION

The invention relates to the field of ventilation of fluids . Still further, this invention relates to that of providing proper exhaust arrangements for flue gases from Chimneys of large kitchens.. Furthermore, the invention relates to usage of multiple suction fans to increase the discharge of hot gases and vapours in large cross sectional ducts with reduced noise during expulsion of gases and vapours.

BACKGROUND OF INVENTION

It can be observed that nowadays there is very huge requirement of chimneys with appropriate mechanisms for draught of the vapours and smoke that emanates from cooking and catering and food processing establishments.

As such establishments are involved in the manufacture and making of food which would be more or less a continuing process which would be an ongoing one almost throughout the year. Further, the sizes of kitchens are very large in establishments, which require to manufacture food in very large quantities for consumption of very large number of people and also, kitches need to function in various shifts employing large number of personnel using cooking gadgets, with varying fuels, which would emanate and discharge different type of exhaust gases during their operation.

With modern equipments used for processing of food, using highly efficient fuels, the occurrence of smoke produced by burning of fuel during kitchen operations has been drastically reduced, and yet, there requires a constant need to systematically eliminate the fuel vapours in a streamlined manner to the atmosphere. Further, the vapours of the edible oil / cooking oil etc which would be emanating during cooking processes of frying, deep-frying, sauting etc the edible oil, which would be boiled to elevated temperatures, might crack into lower fatty acids and in the process would release much vapours, which are having the capacity of adhering to adhering to atmospheric particles, dust in the surrounding regions and over longer period of time, if not properly expelled might leave behind traces of greasy materials in the walls of the kitchen, and surroundings, thus creating a bad ambience and posing air pollution in the areas of the vicinity of the location of the large kitchen. Hence it is imperative to provide an efficient and methodical way of elimination of smoke and vapours to the atmosphere. Conventional methods of elimination of vapours and gases from kitchens through chimney were primarily to let the air and vapour mix to escape just by orienting them towards the chimney which is essentially a progressively tapering, arrangement of fabricated metallic elements, which would receive the air vapour mixture and from the apex of the chimney letting out the same to the atmosphere thus making it to mingle with the air outside.

But it can be always observed that in such type of chimneys, especially in case of large kitchens which produce more air and vapours and gases, as output of the cooking operations, and the vapours being denser than air and having solid particles ( aerosols) in its constituent, they tend to move slower towards the apex point and more over during the path of progress towards the top of the chimney much of the heavier particles of the air vapour mixture, tends to adhere to the walls of the Chimney. Periodic occurrence of such situation would result in the walls of the chimney getting adhered to greasy matter and ultimately the efficacy of the system of expelling the air vapour mixture would get reduced due to clogging of the walls of the chimney.

Hence, it is imperative for adopting methods of modem gas expulsion systems for chimneys of very large kitchens and Split exhaust kitchen chimney is a method by which the exhaust chimney structure is provided in which suction fan mounted at end of the duct pipe in kitchen wall, axial fans suck the burnt gasses through hood and exhaust them directly in same direction

OBJECT OF THE INVENTION:-

Accordingly it is an object of the invention is to provide a split exhaust chimney system for large kitchen which has its hood mounted directly over the gas burner.

Still further it is another object of the invention to provide powerful axial fans to kitchen chimney ducts, so that they can suck the burnt gases from the stove directly through a piped duct.

More particularly it is yet another object of the invention to force, the sucked burnt gases exhaust in same direction to outside in streamlined manner and sending the burnt gases from the stove straight to the outside to achieve the best solution for having healthy pollution free kitchen.

DESCRIPTION OF THE INVENTION

Accordingly, the split exhaust chimney whose primary purpose is to reduce the noise during expulsion of gases and vapours. The Multiple suction fans increase the discharge of hot gasses and vapours in large cross sectional ducts and provide a higher suction power and for vent the solid waste from exhaust fans.

Split exhaust kitchen chimney is the exhaust chimney in which suction fan mounted at end of the duct pipe in kitchen wall, axial fans suck the burnt gasses through hood and exhaust them directly in same direction. A drastic reduction in noise can thus be achieved.

Split exhaust kitchen chimney has a chimney hood mounted directly over the gas burner At the end of this kitchen chimney duct has a powerful axial fans they suck the burnt gases from the stove directly through a piped duct. The sucked burnt gases exhaust in same direction to the outside. The burnt gases are sent from the stove straight to the outside in streamlined manner is best solution to have healthy pollution free kitchen.

By this arrangement a Noise free, with optimally reduced decibel effects, which is easy for maintenance with Optimally reduced vibration and Optimally improved exhaust.

The Fans can be arranged in any direction ( horizontal, Vertical and cross ) and the number of fans depends on the cross sectional area of the duct pipe. There need not be

any restriction on chimney size but size of the exhaust fan is restricted.

Accordingly, as per fig 1, the Kitchen Platform (1) with chimney arrangement with plurality of fans (5) with a ducting arrangement (3) and the hood of the chimney (2) is placed above the kitchen platform (1) and a mesh arrangement (4) is provided for the draught of air by the fans (5).

Calculation of Chimney Size and Limitations

The split chimney size is calculated with reference to standard size of electric chimney . Accordingly

Duct size : No restriction it can be from 1’ to any size Chimney size : No restriction any size and any position for comfort.

Fan power: No limitation, depends on suction capacity is required.

Ratio between pipe size to duct size : 1:2

Type of fan: No restriction any type of fan, Axial fan for domestic and Centrifugal for commercial.

The most important specification of kitchen chimney is its suction power. The suction capacity of electric chimney is in m /hr. As a rule of thumbs, the capacity of an electric kitchen chimney should be able to suck out at least 10 times the volume of air in the kitchen per hour.

Example: 4mx 4mx 2.5m=40m

Fresh air equality to kitchen volume have to replaced 10 times in an hour l0x40m³/h=400 m³/h. So, the kitchen requires minimum 400 m³/h.

Modifications to improve chimney suction power.

Higher the chimney suction power for given size of chimney efficient is the chimney.

Kitchen chimney with wide duct has effective suction power

To expel more smoke, vapours and odor requires more suction power, it can be possible by multi suction system

Precautions

Factors that affects the suction power:

a). Duct in size, length and diameter

b). Number of bends in duct

Suction power can be improved by providing multi suction system with different orientations of fans

Tapered cross sections at comers and throughout the length of the chimney can be improved suction power.

CHIMNEY CALCULATION

Case 1 Calculations for Natural Draft

Air Flow and Air Velocity!

the air velocity through the duct

the air flow volume through the duct

where

q = air volume (m3/s)

po = density outside air (kg/m3)

pr =density inside air (kg/m3) l = Darcy-Weisbach friction coefficient

l = length of duct or pipe (m, ft)

dh = hydraulic diameter (m, ft)

å x = minor loss coefficient (summarized)

Natural Draft Head:

The natural draft head can be calculated as dhmmH20 = 1000 h (po - pr) / ph2o where dhmmH20 = head in millimeter water column (mm H20). h = height between outlet and inlet air (m)

Natural Draft Pressure dp = g (po - pr) h where = pressure (Pa, N/m2)

g = acceleration of gravity - 9.81 (m/s2)

Density and Temperature:

With air density 1.293 kg/m3 at OoC - the air density at any temperature can be expressed as

p = (1.293 kg/m3 ) (273 K) / (273 K + t)

or

p = 353 / (273 + t) (2b)

where

p = density of air (kg/m3)

t = the actual temperature (oC)

Major and Minor System Loss:

The natural draft force will be balanced to the major and minor loss in ducts, inlets and outlets. The major and minor loss in the system can be expressed as dp = l (l/dh) (P_r v2 / 2) + Sx 7/2 p_r v2 where dp = pressure loss (Pa, N/m², Ib/ft²)

Air Flow and Air Velocity:

air velocity through the duct v = [(2 g (po

the air flow volume through the duct

where q = air volume (m³/s)

To find air velocity : g = acceleration of gravity - 9.81 (m/s²)

P_o = density outside air (kg/m³) p_r = density inside air (kg/m³) air density 1.293 kg/m³ at 0°C at 27°C po = p (27°C)= 1. 17663 kg/m³

p_r = p(100 °C)=0.94635 kg/m³ h = height between outlet and inlet air (m)

h=1 m

l =0.019

I = length of duct or pipe =1.5m

p_r =0.94635 kg/m³

d_h =300 mm=.3m

å x = minor loss coefficient = 1

q = 0.9147 m³/s

CASE II: CALCULATIONS FOR FORCED DRAFT

Speed of the impeller N= 1440rpm

Diameter of the chimney d= 300mm =0.3m

Velocity of the air in duct V=ndn/60 m/s

= GR0.3^*1440/60

=22.619m/s.

Rate of air flow through the duct Q= A^*V

=(P/4) D2^*V

=1 59m3/s.

Efficiency of the fan:

Fan efficiency =work done isentropically /actual work done.

Claims

where r=pressure ratio= pO / pr

p0= po g hi

p0=1.17663 ^*9.81 ^*1 .52=17.59 N/m2

pr= pr g h2 pr= .9635 ^*9.81 ^*2.52 = 29.09 N/m2 r=pressure ratio= pO /pr = 1 .6575

Y = adiabatic index = 1 .4

R= gas constant = 0.287 KJ/KgK

Therefore Efficiency of fan = Cp/R((r)(Y-1 )/Y-1 ) /(Y-1 )

Cp = Specific heat of air at constant pressure =1 .008 KJ/KgK

Efficiency= .8297=82.97%

Claims

What is claimed

1) A chimney primarily intended for kitchens with plurality of suction fans for

achieving reduction of noise during expulsion of gases and vapours, the Multiple suction fans of the said chimney increase the rate of discharge of hot gases and vapours in large cross sectional ducts and provide a higher suction power and for vent the solid waste from exhaust fan, comprising of,

a chimney hood mounted directly over the gas burner , the rear portion / end of the said kitchen chimney duct has a powerful axial fans for sucking of the burnt gases from the stove directly through a piped duct ;

the sucked burnt gases exhaust are drafted in streamlined manner in a direction similar to the exit outlets enabling the burnt gases are sent from the stove straight to the outside in streamlined manner to enabea healthy and pollution free kitchen

2) The said chimney as claimed in claim 1, provides a noise free environment, with optimally reduced decibel effects, which is easy for maintenance with Optimally reduced vibration and Optimally improved exhaust.

3) The plurality of fans of the said chimney, as claimed in claim 1, can be arranged in any direction ( horizontal, Vertical and cross ) and the number of fans depends on the cross sectional area of the duct pipe wherein there need not be any restriction on chimney size but size of the exhaust fan is restricted.

4) The suction capacity of the said chimney is in m /hr wherein a rule of thumbs, the capacity of an electric kitchen chimney should be able to suck out at least 10 times the volume of air in the kitchen per hour

5) The said chimney as claimed in claim 1 wherein higher suction power for given size of chimney efficient is the chimney and chimney with wide duct has effective suction power To expel more smoke, vapours and odor requires more suction power, it can be possible by multi suction system