boys gas calorimeter

7/21/2019 Boys Gas Calorimeter

http://slidepdf.com/reader/full/boys-gas-calorimeter 1/11

INTRODUCTION

Boy’s gas calorimeter is a simple apparatus that is suitable for

determining caloric alue of gaseous fuels! This apparatus "as named

after an #nglish physicist and inentor $%ir Charles &ernon boys’ '()(*+!

,rom this- "e can calculate both the lo"er caloric alue as "ell

as the higher caloric alue of gases!

Calorimetry is the science of measuring heat! Caloric alue isdened as the amount of energy released after burning (.g of fuel!

There are t"o types of caloric alues as I stated earlier!

(! /igher caloric alue'/C&+0 It is the total heat liberated by the complete

combustion of (.g of fuel! This is determined by

bringing all the products of combustion bac. to pre

combustion temperature! '1eans condensing any

"ater apor produced!+ In higher caloric alue "e

assume that "ater is in a li2uid state after

combustion and it absorbs some amount of heat to

ma.e that li2uid "ater into apor "ater! This heat

is .no"n as the latent heat of apori3ation!4! 5o"er caloric alue '5C&+

0 It is the di6erence of higher caloric alue and heat

absorbed by "ater apors! This treats as any /4O

formed as apor! The energy re2uired to apori3e

"ater is therefore not released as heat!



If the condensation part of the boy’s gas colorimeter "or.s properly "e

can nd the higher caloric alue! If "ater remains in the apor phase

then the lo"er caloric alue is sought!

Apparatus

Calorimeter Rotameter



1anometer ,lo" control deice



Procedure

7pparatus "as set up and necessary properties and constants "ere

noted do"n! 7fter setting rotameter alue for ('for steady combustion+ "e open

the gas 8o" and ignite the burner

Calorimeter "as placed properly and "ater circulation process "as

started! 9e .ept the apparatus for about :; minutes to ensure steady

conditions! 7fter that inlet temperature- outlet temperature and e<haust gas

temperature "as noted do"n! =as pressure "as read by the manometer!

9ater circulated "as collected to buc.et for > minutes and

measured!

Repeat this procedure for : minutes!

Equations for calculation

&olume of gas ? =as 8o" rate × time × (;0@ m:

7bsolute pressure ? =auge pressure A 7tmospheric pressure '(;(:4>

pa+

Conerting gas olume into standard conditions

P1V

1

T 1= P

2V

2

T 2

Temperature di6erence ? outlet temperature inlet temperature

m×C p×temperature difference=calorific value×standard volume

Calorificvalue=m×C p×temperaturedifference

standard volume



Calculations

C p Of "ater !(*@ Eg.

Conersion of gas olume into standard conditions

Fgauge ? G < (;0: < ;!*4@ < (;;; < )!*( ? >@!G4 pa

Fabsolute ? (;(:4> A >@!G4 ? (;(:*(!G4 pa

,uel olume ? (!(4> < > < (;0@

P1V

1

T 1= P

2V

2

T 2

101381.72×1.125×5 x10−6

31+273=

1.023 X 105×V 2

300

&4 ? >!>;(4 < (;0@

%imilarly-

Pabsolute 101381.72 101406 101446

Volue!standard"

>!>;(4 < (;0@ *!:>:) < (;0@ ((!@*)> < (;0@

Calculation of caloric alue

()G; Hg < !(*@ HEg. <:. ?C v <>!>;(4 < (;0@Hm:

C ? )G 1Em:

%imilarly



#ei$%t of

&ater!$"

'eperatur

e

di(erence!)

"

*tandard

+olue!3"

Calori,c

+alue!-/3

"

170 : >!>;(4 < (;0@ )G

1740 @ *!:>:) < (;0@ >4:(!:(

2140 >((!@*)> < (;0

@ :*:(!@



iscussion

Fractical errors

9hen "e are calculating the caloric alue- "e assumed thatenergy released by burning fuel is all absorbed by the "ater to increase

its temperature! But it is not the case here! If the di6erence bet"een

the e<haust temperature and room temperature is so high- the amount

of heat loss through e<haust is not negligible! 9e can only assume that

e<haust gas temperature is almost e2ual to ambient temperature! If it is

the case since e<haust and atmosphere are in thermal e2uilibrium- "e

can state that there is no heat loss! But this is not the case in our

practical! But "e neglect e<haust heat loss! It "as an error in our

practical!

#en though "e did our calculations assuming fuel is burning

completely it is not true! 9hile "e’re doing the practical "e sa" blac.

smo.es or fumes coming out of the e<haust- indicating that it is an

incomplete burning process! This is also a practical error!

7s I stated in the introduction- in order to state that the alue "e

obtain is the higher caloric alue- "e need to ma.e sure that all the

"ater apor is condensed inside! But in our apparatus the condensing

part "as bro.en and "e cannot guarantee full condensation- "hichresults our data deiate from theoretical alues!

Other methods of nding caloric alue

(! ,or solid or li2uid fuel

Caloric alues of solid and li2uid fuels are generally

determined using a Bomb calorimeter! It resembles the shapeof bomb and thus .no"n as the bomb calorimeter!



/ere fuel is burnt in a strong steel chamber "hich is

immersed in a .no"n mass of "ater! The fuel sample is ignited

by an electrically heated platinum "ire! Then temperature

readings should be ta.en for eery (; seconds!

The heat released by combustion is absorbed by

surrounding "ater! Thus by balancing energy "e can nd the

caloric alue!

7nother apparatus to nd the caloric alue of solid fuel isthe Thompson calorimeter!

4! ,or gaseous fuel

Caloric alue of gaseous fuel is determined by $Jun.er’s or

boy’s’ calorimeter!



The metered gaseous fuel is continuously supply to the

calorimeter at constant pressure "here it burns in the

presence of air! Circulating "ater through the apparatus

absorbs the heat generated by burning fuel! Thus by energy

balance caloric alue of fuel is obtained!



Ener$ balance for t%e sste

Kfuel ? /eat from burned fuel

K"ater ? heat absorbed by circulating "ater

Kloss through "alls ? heat transferred through the "alls of calorimeter by

conduction- conection and radiation

Kloss-e<haust ? /eat loss to atmosphere through e<haust gas

Kfuel ? K"ater A Kloss through "alls A Kloss-e<haust

Ener$ 1 2 3

eat ener$added !"

:GG:;!:> >G4)>!* *;(G:!4>

eat ener$

absorbed b

coolin$ &ater !"

4G:) :G;( G);

osses (4))(!:> (:>)!* :>:*:!4>

boys gas calorimeter

Documents