Thermal cond0ctivity is the meas0re of the a1ility of a material to allo2 the flo2 of heat from its 2armer s0rface thro0gh the material to its colder s0rface3 it is determined as the heat energy transferred per 0nit of time and per 0nit of s0rface area divided 1y the temperat0re gradient+ Temperat0re gradient is defined as the difference of temperat0re divided 1y the distance 1et2een the t2o s0rfaces 0s0ally e4pressed in 2atts per .elvin per meter+ The o15ectives of this e4periment are to determine the thermal cond0ctivity and efficiency of the lagging materials+ The heat inp0t 2o0ld 1e ass0med e60al to the heat flo2 rate thro0gh the lagged pipe+ The material 1eing 0sed in this e4periment is the 1are and lagged pipes set70p apparat0s) 1oiler) digital thermometers) heat resistant gloves) container and steam condensate collector+
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INTRODUCTION
-eat transfer is the movement of thermal energy from one thing to another thing of different temperat0re+ These o15ects co0ld 1e t2o solids) a solid and a li60id or gas) or even 2ithin a li60id or gas+ -eat transfer 1y cond0ction involves transfer of energy 2ithin a material 2itho0t any motion of the material as a 2hole+ Energy transfers from more energetic to less energetic molec0les 2hen neigh1o0ring molec0les collide+ -eat flo2s in direction of decreasing temperat0res since higher temperat0res are associated 2ith higher molec0lar energy+ The rate of heat transferred nat0rally depends on the magnit0de of the temperat0re difference) the thermal resistance) and the heat transfer area+ The 0se of ins0lation is the most common method of minimi8ing the heat losses to the s0rro0ndings+ This increases the resistance therefore lo2er the rate of heat transfer+ The rate of heat lost from a pipe carrying steam can 1e meas0red simply 1y determining the rate of condensation of steam) m) 2hich can 1e collected at a certain interval of time+
Condensed steam can 1e collected as sat0rated li60id 0nder controlled conditions) then 2e can simplify the a1ove e60ation to) 9 s
Determining the effectiveness of ins0lation 2o0ld therefore 1e 50st comparing the heat lost from the pipe 2ith ins0lation 2ith that of a 1are pipe+ The rate of condensation 2o0ld 1e proportional to the heat lost and the 2eight of the condensate is directly proportional to its vol0me+ This is ass0ming that the temperat0res and press0res of the condensate are the same+ The lagging efficiency co0ld 1e determined 0sing the e60ation
"efore heat is transferred to the s0rro0ndings) it travels first from the 10lB of the steam thro0gh the steam film condensate) then thro0gh the metal pipe) then thro0gh the ins0lation 1y cond0ction 0ntil it reaches the s0rface of the ins0lation 2here part of the heat is transferred to the s0rro0nding air 1y convection and part 1y radiation to the s0rro0nding 2alls+ That is) 9 9 ; 9 ℎ<< = > ; ℎ< = >
@here' hc 9 -eat transfer coefficient 1y convection hr 9 -eat transfer coefficient 1y radiation Ts 9 S0rface temperat0re of ins0lation Ao 9 O0tside area of ins0lation or practical p0rposes) Ta 9T2 ) therefore 1ecomes) 9 <ℎ ; ℎ > < = >
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%aterials E60ipments Needed'
+ "are and !agged Pipe Apparat0s Set7 Up + "oiler + Digital Thermometers F+ -eat Resistant (loves G+ Container H+ Steam Condensate Collector
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PROCEDURE
The 1are and lagged pipe apparat0s set7 0p 2as preheated for five min0tes 1y allo2ing the steam thro0gh the t01es 0ntil the temperat0re reading 1ecomes sta1le+ The valves 2ere then opened at the end of each t01e+ Then) a constant press0re of the incoming team 2as set 1y ad50sting the valve that controls the steam inflo2+ This 2as done 1y closing the valves at the end of the t01es and meas0ring the press0re 2hen it 1ecomes constant+ The corresponding temperat0re 2as also meas0red+ The valves at the end of the t01es 2ere opened and the steam 2as allo2ed to r0n thro0gh for five min0tes+ The condensates at the end of the t01es 2ere collected 0sing a metal 1asin+ After five min0tes) the temperat0re at the inlet and o0tlet of the t01es 2ere recorded 0sing thermometers+ The temperat0re and the vol0me of the condensate 2ere meas0red+ The temperat0re of the condensate 2as immediately recorded as it drops into the metal 1asin so that the minimal heat is lost 0pon meas0rement
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RESU!TS AND DISCUSSION
At the Boiler:
Press0re' F PSI Temperat0re ' FoC Pipe Type Inlet Temperat0re O0tlet Temperat0re Pipe ' Perlite F+ Pipe ' Normal J J+H Pipe ' Three <> Times JF JK Coated Pipe F' Ins0lated F+ FF Ta1le ' Inlet and O0tlet Temperat0re Readings per type of Pipe
Pipe Type
Time
GK+ KH
*ol0me of the Condensate &G& G&
KG+
G&
H
FG&
Temperat0re
Pipe ' Perlite & Pipe ' Normal & Pipe ' Three <> & Times Coated Pipe F' Ins0lated & Ta1le ' *ol0me of the Condensate Readings
Pipe Type Pipe ' Perlite Pipe ' Normal Pipe ' Three <> Times Coated Pipe F' Ins0lated Ta1le ' E4perimental -eat !ost per Pipe
-eat !ost HJ+K G+G G+J H&+FG
Pipe Type Pipe ' Perlite Pipe ' Three <> Times Coated Pipe F' Ins0lated Ta1le F' !agging Efficiency
Efficiency H K HF
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CONC!USION
It can 1e concl0ded that the determined e4perimental and theoretical heat losses for each pipe sho2s reasona1ly same res0lts thro0gh the 0se of the heat transfer coefficient for convection and radiation in comp0ting for heat losses+ Pipe F) the Ins0lated Pipe) gave the highest lagging efficiency among all the pipes+
