3rd Group Meeting VIVA M.Phil Transfer 2010 2nd Draft
Lecture 03: STKM3212
1. LECTURE NOTES 03/07 STKM3212: FOOD PROCESSING TECHNOLOGY MASS AND HEAT TRANSFER IN STEADY STATE (Perpindahan Jisim dan Tenaga Haba dalam Keadaan Mantap) SAIFUL IRWAN ZUBAIRI PMIFT, Grad B.E.M. B. Eng. (Chemical-Bioprocess) (Hons.), UTM M. Eng. (Bioprocess), UTM ROOM NO.: 2166, CHEMISTRY BUILDING, TEL. (OFF.): 03-89215828, FOOD SCIENCE PROGRAMME, CENTRE OF CHEMICAL SCIENCES AND FOOD TECHNOLOGY, UKM BANGI, SELANGOR
29. CONTINUE: As if, A 2 /A 1 > 1.5 ----------- As if, A 2 /A 1 < 1.5 ----------- A 1m = A 1 + A 2 /2 Cylinder resistance ------------ = A 2 - A 1 /In (A 2 /A 1 ) LOG MEAN AREA Unit R = K/W
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34. CONTINUE: Radial heat flow through multiple cylinders in series METAL TUBE WALL = A INSULATED 1 = B INSULATED 2 = C
35. CONTINUE: Where: COMBINE the equations to eliminate T 2 and T 3 . SO, THE FINAL EQUATION R = The overall resistance is the SUM of individual resistances in series
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38. CONTINUE: . Asbestos (B) Stainless Steel (A) Inside the pipe (fluid or gas flow) r 1 r 2 r 3 0.0254 m q
42. CONTINUE: The HEAT TRANSFER RATE is using the combination of CONVECTIVE and CONDUCTION Expressing 1/ h i A , xA /k A A and 1/h o A = R (resistances) and combine:
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44. CONTINUE: The overall heat transfer by combined CONDUCTION & CONVECTIVE is often expressed in terms of an OVERALL HEAT TRANSFER COEFFICIENT (U) defined by : T overall = T 1 - T 4 A more important application is heat transfer from a fluid outside a cylinder through a METAL WALL and to a fluid inside the TUBE, as often occurs in “ HEAT EXCHANGER ” ------ REFER FIG 4.3-3 (b)
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47. CONTINUE: Lagging (B) Stainless Steel (A) Inside the pipe (saturated steam flow), T i = 267 0 F T 0 = 80 0 F Surrounding Fluid A r i r 1 r 0 1.5 in. q
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50. CONTINUE: = SO: = q = 29.8 btu/hrs R B = k B .A BIm r 0 - r 1 ----------- 0.169 - 0.044 --------------------- 0.037(0.583) = 5.80 R 0 = h 0 .A 0 1 = 1 2(1.060) ------------ = 0.472 ------- q = T i - T 0 R i + R A + R B + R 0 ------------------------- 267 - 80 --------------------------------------------------- 0.00464 + 0.00148 + 5.80 + 0.472
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