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CHAPTER 4 1958 Guide; 88 i f Fluid Meters, Their Theory and Application (American Society of Mechanical; Eng3 iFnleoewrsM, e4athsuEredmiteionnt,,P1o9w3e7)r. Test Codes, Part 5, Chap. 4 (American Society of M. e,, cha4nSictanl dEanrgdisnefeorrs,D1is9c4h9)a.rge Measurement (National Advisory Committee for Aero n1a93u2ti)c.s, NACA Tech. Mem. 952,1940) (Translation of German Industrial Standard Js 3 Gas Measurement Committee Report No. 2, Natural Gas Department (Amer- '> ican Gas Association, 1948). \ 4 The Flow Mechanism and Performance of the.Rotameter, by E. M. Schoenborn,; s Jr. and A. P. Colburn (Institute of Chemical Engineers, Transactions, 35, 1939, 359- , 381). ,i BIBLIOGRAPHY . [A] Thermodynamics, by Edward F. Obert (McGraw-Hill Book Company, 1948). f [B] Thermodynamics of Fluid Flow, by Newman A. Hall (Prentice-Hall, Inc., 195[C1)]. Fluid Mechanics, by Russell A. Dodge and Milton J. Thompson (McGraw- Hil[lDB] oFolkuiCdoM.,e1c9h3a7n)i.cs, by R. C. Binder (Prentice-Hall, Inc., 2nd Edition, 1949). 1[E] The Physics of Solids and Fluids, by P. P. Ewald, H. Poschl and L. Prandtl & (B- l[aFc]kAie,S1t9u3d6y).of the Data.on the Flow of Fluidsjn Pipes, by Emory Kemler, Hy-fe didreamul.ic, 5P5a, pNeor.H1Y0,D2-35-53-22, 1(A93.S3)..M.E. Transactions 55, No. 10, 7-22, 1933; Discussion, aI nee[Grin] gTh65e, F1i9o3w3,o4f9F7-l5u0id1,s5in15C).losed Conduits, by R. J. S. Pigott (Mechanical Engi- .3'j [H] Fluid Meters, Their Selection and Installation (American Society of Mechanical m Engineers, 1933). If [I] The Orifice Meter for Measurement of Flow of Gases and Liquids, by Allen D M Ma[cJL]ePanito(tPTitutsbbeuPrgrahcEticqeu,itbayblEedMweatredr SC.oC.,o1le93(8A)..SM.E. Transactions 67, 1935, 281--f3j 294; Discussion, idem. 68, 1936, 146-156). M [K] Pitot Tubes in Large Pipes, by Edward S. Cole and E. Shaw Cole (A.S.M.eM Transactions, 61,1939, 465--173; Discussion, idem. 61, 1939, 473--475). L] Investigation of Errors of Pitot Tubes, by C. W. Hubbard (A.S.M.E. TransA act[ioMn]s,P6ip1,in4g77A-r4r9a7n;gDemisceunstssiofonr, Aidcecmep. t6a1b,le19F3l9o,w4m97e-t5e0r6A).ccuracy, by R. E. SprenkleSa_ (A.S.M.E. Transactions, 67, 345-357,1945; Discussion, idem. 67, 357-360, 1945). |3 CHAPTER 5 HEAT TRANSFER Conduction, Convection, Radiation; Equations for Conduction, Convection, Radi ation and Combined Convection and Radiation; Heat-Flow Resistance, in Series and Parallel; Practical Heat Transfer Problems; Periodic and Transient Heat Flow HEAT is the form of energy that is transferred by virtue of an existing temperature difference. The temperature difference is the potential which causes the transfer, the latter in turn being resisted by the thermal properties of the material combined in a single term known as the resist ance. Energy exchange associated with evaporation, condensation, etc., is treated elsewhere such as in the section on cooling lower design in Chapter 34. The objectives of this chapter are to: 1. Describe the mechanisms and present the rate equations for the different modes of heat transfer. 2. Illustrate the application of the basic concepts to steady-state problems (tem perature independent of time or a cyclic variable thereof.) by means of several typical solutions of heat transfer systems. 3. Present concise summaries of available methods of analysis for transient and periodic heat transfer problems. Further applications to specific systems will be found throughout The Guide. CONDUCTION, CONVECTION AND RADIATION Thermal conduction is the term applied to the mechanism of heat trans fer whereby the molecules of higher kinetic energy transmit part of their energy to adjacent molecules of lower kinetic energy by direct molecular action. Since the temperature is proportional to the average kinetic energy of the molecules, thermal transfer will occur in the direction of decreasing temperature. The motion of the molecules is random; there is no net material flow associated with the conduction mechanism. In the case of flowing fluids, thermal conduction is significant in the region very close to a solid boundary or wall, for in this region the flow is laminar, parallel with the wall surface, and there are practically no cross currents '"i d Kd^eCtin ^ie heat transfer across the solid fluid boundary. In solid bodies the significant mechanism of heat transfer is always thermal conduction. Contrasted to the thermal conduction mechanism, thermal convection involves energy transfer by eddy mixing and diffusion1 in addition to nduction. This is shown schematically in Fig. 1 which exhibits transfer om a pipe wall at surface temperature L to a colder fluid at a bulk tem- flnlH f6 tf' temperature is that which would be attained if the som ?vere drawn off at a certain section and mixed. It is therefore mgher than the lowest temperature in the stream.) In the oecur^sublayer, immediately adjacent to the wall, the heat transfer the bSff l erma'l conduction; in the transition region, which is called utter layer, eddy mixing as well as conduction effects are significant; 89