This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Chap 13 Heat Exchangers Review Problems 13111 Hot oil is cooled by water in a multipass shellandtube heat exchanger. The overall heat transfer coefficient based on the inner surface is to be determined. Assumptions 1 Water flow is fully developed. 2 Properties of the water are constant. Properties The properties of water at 300 K 25 C are (Table A9) 14 . 6 Pr /s m 10 894 . / C W/m. 607 . 2 6 = = = = k Analysis The Reynolds number is 771 , 43 /s m 10 894 . ) m 013 . )( m/s 3 ( Re 2 6 = = = D V m which is greater than 10,000. Therefore, we assume fully developed turbulent flow, and determine Nusselt number from 245 ) 14 . 6 ( ) 771 , 43 ( 023 . Pr Re 023 . 4 . 8 . 4 . 8 . = = Nu and C . W/m 440 , 11 ) 245 ( m 013 . C W/m. 607 . 2 = = = Nu D k h i The inner and the outer surface areas of the tube are A D L A D L i i o o = = = = = = ( . )( ) . ( . )( ) . 0 013 1 0 04084 0015 1 004712 m m m m m m 2 2 The total thermal resistance of this heat exchanger per unit length is C/W 609 . ) m 04712 . )( C . W/m 35 ( 1 ) m 1 )( C W/m. 110 ( 2 ) 3 . 1 / 5 . 1 ln( ) m 04084 . )( C . W/m 440 , 11 ( 1 1 2 ) / ln( 1 2 2 2 2 = + + = + + = o o i o i i A h kL D D A h R Then the overall heat transfer coefficient of this heat exchanger based on the inner surface becomes C . W/m 40.2 2 = = = = ) m 04084 . )( C/W 609 . ( 1 1 1 2 i i i i RA U A U R 1387 Outer surface D , A , h , U Inner surface D i , A i , h i , U i Chap 13 Heat Exchangers 13112 Hot oil is cooled by water in a multipass shellandtube heat exchanger. The overall heat transfer coefficient based on the inner surface is to be determined. Assumptions 1 Water flow is fully developed. 2 Properties of the water are constant. Properties The properties of water at 300 K 25 C are (Table A9) 14 . 6 Pr /s m 10 894 . / C W/m. 607 . 2 6 = = = = k Analysis The Reynolds number is 771 , 43 /s m 10 894 . ) m 013 . )( m/s 3 ( Re 2 6 = = = D V m which is greater than 10,000. Therefore, we assume fully developed turbulent flow, and determine Nusselt number from 245 ) 14 . 6 ( ) 771 , 43 ( 023 . Pr Re 023 . 4 . 8 . 4 . 8 . = = Nu and C . W/m 440 , 11 ) 245 ( m 013 . C W/m. 607 . 2 = = = Nu D k h i The inner and the outer surface areas of the tube are A D L A D L i i o o = = = = = = ( . )( ) . ( . )( ) . 0 013 1 0 04084 0015 1 004712 m m m m m m 2 2 The total thermal resistance of this heat exchanger per unit length of it with a fouling factor is C/W 617 . ) m 04712 . )( C . W/m 35 ( 1 m 04712 . C/W . m 0004 . ) m 1 )( C W/m. 110 ( 2 ) 13 / 15 ln( ) m 04084 . )( C . W/m 440 , 11 ( 1 1 2 ) / ln( 1 2 2 2 2 2 2 , = + + + = + + + = o o o o f i o i i A h A R kL D D A h R Then the overall heat transfer coefficient of this heat exchanger based on the inner surface becomes C . W/m 39.7 2 = = = = ) m 04084 . )( C/W 617 . ( 1 1 1 2 i i i i RA U A U R 1388 Outer surface...
View Full
Document
 Spring '06
 Rajadas

Click to edit the document details