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Fin

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Abraham Mansouri

The document discusses calculating the increase in heat transfer from tubes due to adding circular aluminum alloy fins. It provides the properties of the fins, assumptions about operating conditions and heat transfer, and the analysis to determine the heat transfer from a single fin and the total heat transfer from the finned tube. The increase in heat transfer per meter of the tube length due to the fins is determined to be 5380 W, representing a factor of 10 increase over the unfinned tube. This explains the widespread use of finned surfaces to enhance heat transfer.

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PROPRIETARY MATERIAL. 息 2011 The McGraw-Hill Companies, Inc. Limited distribution permitted only to teachers and educators for course preparation. If you are a student using this Manual, you are using it without permission. 3-113 m0942.0)m1)(m03.0( 2 1fin LDA The efficiency of these circular fins is, from the efficiency curve, Fig. 3-44 3-166 Circular aluminum alloy fins are to be attached to the tubes of a heating system. The increase in heat transfer from the tubes per unit length as a result of adding fins is to be determined. Assumptions 1 Steady operating conditions exist. 2 The heat transfer coefficient is constant and uniform over the entire fin surfaces. 3 Thermal conductivity is constant. 4 Heat transfer by radiation is negligible. Properties The thermal conductivity of the fins is given to be k = 180 W/m 属C. Analysis In case of no fins, heat transfer from the tube per meter of its length is no W537C)25120)(m0942.0)(C.W/m60()( 22 finnofinno TThAQ b 96.0 207.0 m)C)(0.002W/m180( CW/m60 2 002.0 015.0 2 07.2 0.015 )2/002.0(03.0)2/( m015.02/)03.006.0(2/)( fin o o2 2/1 2/3 1 2 12 kt ht L kA h L r tr DDL p c eat transf from a single fin is 22 finfinmaxfin,finfin 2 TThAQQ b gle unfinned portion of the tube is 2 1fin sDA here are 200 fins and thus 200 interfin spacings per meter length of the tube. The total heat transfer from the finned tube is Therefore, the increase in heat transfer from the tube per meter of its length as a result of the addition of the fins is Discussion The The overall effectiveness of the finned tube is 5380/537 = 10. That is, the rate of heat transfer from the steam tube increases by a factor of 10 as a result of adding fins. This explains the widespread use of finned surfaces. H er C)25120)(m004624.0)(C.W/m60(96.0 )( m004624.0)002.0)(03.0(2)015.003.0(22)(2 22 2 2 1 2 2fin trrrA W3.25 Heat transfer from a sin W6.1C)25120)(m000283.0)(C.W/m60()( 22 unfinunfin TThAQ b m000283.0m)m)(0.00303.0(un T then determined from W5380)6.13.25(200)( unfinfinfintotal, QQnQ W48435375380finnofintotal,increase QQQ

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Fin

  • 1. PROPRIETARY MATERIAL. 息 2011 The McGraw-Hill Companies, Inc. Limited distribution permitted only to teachers and educators for course preparation. If you are a student using this Manual, you are using it without permission. 3-113 m0942.0)m1)(m03.0( 2 1fin LDA The efficiency of these circular fins is, from the efficiency curve, Fig. 3-44 3-166 Circular aluminum alloy fins are to be attached to the tubes of a heating system. The increase in heat transfer from the tubes per unit length as a result of adding fins is to be determined. Assumptions 1 Steady operating conditions exist. 2 The heat transfer coefficient is constant and uniform over the entire fin surfaces. 3 Thermal conductivity is constant. 4 Heat transfer by radiation is negligible. Properties The thermal conductivity of the fins is given to be k = 180 W/m 属C. Analysis In case of no fins, heat transfer from the tube per meter of its length is no W537C)25120)(m0942.0)(C.W/m60()( 22 finnofinno TThAQ b 96.0 207.0 m)C)(0.002W/m180( CW/m60 2 002.0 015.0 2 07.2 0.015 )2/002.0(03.0)2/( m015.02/)03.006.0(2/)( fin o o2 2/1 2/3 1 2 12 kt ht L kA h L r tr DDL p c eat transf from a single fin is 22 finfinmaxfin,finfin 2 TThAQQ b gle unfinned portion of the tube is 2 1fin sDA here are 200 fins and thus 200 interfin spacings per meter length of the tube. The total heat transfer from the finned tube is Therefore, the increase in heat transfer from the tube per meter of its length as a result of the addition of the fins is Discussion The The overall effectiveness of the finned tube is 5380/537 = 10. That is, the rate of heat transfer from the steam tube increases by a factor of 10 as a result of adding fins. This explains the widespread use of finned surfaces. H er C)25120)(m004624.0)(C.W/m60(96.0 )( m004624.0)002.0)(03.0(2)015.003.0(22)(2 22 2 2 1 2 2fin trrrA W3.25 Heat transfer from a sin W6.1C)25120)(m000283.0)(C.W/m60()( 22 unfinunfin TThAQ b m000283.0m)m)(0.00303.0(un T then determined from W5380)6.13.25(200)( unfinfinfintotal, QQnQ W48435375380finnofintotal,increase QQQ