heat and mass transfer 4e by cengel solution manual

**4-1 Chapter TRANSIENT HEAT CONDUCTION Lumped System Analysis 4-1C In heat transfer analysis, some bodies are observed to behave like a "lump" whose entire body temperature remains essentially uniform at all times during a heat transfer process The temperature of such bodies can be taken to be a function of time only Heat transfer analysis which utilizes this idealization is known as the lumped system analysis It is applicable when the Biot number (the ratio of conduction resistance within the body to convection resistance at the surface of the body) is less than or equal to 0.1 4-2C The lumped system analysis is more likely to be applicable for the body cooled naturally since the Biot number is proportional to the convection heat transfer coefficient, which is proportional to the air velocity Therefore, the Biot number is more likely to be less than 0.1 for the case of natural convection 4-3C The lumped system analysis is more likely to be applicable for the body allowed to cool in the air since the Biot number is proportional to the convection heat transfer coefficient, which is larger in water than it is in air because of the larger thermal conductivity of water Therefore, the Biot number is more likely to be less than 0.1 for the case of the solid cooled in the air 4-4C The temperature drop of the potato during the second minute will be less than 4°C since the temperature of a body approaches the temperature of the surrounding medium asymptotically, and thus it changes rapidly at the beginning, but slowly later on 4-5C The temperature rise of the potato during the second minute will be less than 5°C since the temperature of a body approaches the temperature of the surrounding medium asymptotically, and thus it changes rapidly at the beginning, but slowly later on 4-6C Biot number represents the ratio of conduction resistance within the body to convection resistance at the surface of the body The Biot number is more likely to be larger for poorly conducting solids since such bodies have larger resistances against heat conduction 4-7C The heat transfer is proportional to the surface area Two half pieces of the roast have a much larger surface area than the single piece and thus a higher rate of heat transfer As a result, the two half pieces will cook much faster than the single large piece 4-8C The cylinder will cool faster than the sphere since heat transfer rate is proportional to the surface area, and the sphere has the smallest area for a given volume 4-9C The lumped system analysis is more likely to be applicable in air than in water since the convection heat transfer coefficient and thus the Biot number is much smaller in air PROPRIETARY MATERIAL © 2007 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 4-35 4-10C The lumped system analysis is more likely to be applicable for a golden apple than for an actual apple since the thermal conductivity is much larger and thus the Biot number is much smaller for gold 4-11C The lumped system analysis is more likely to be applicable to slender bodies than the well-rounded bodies since the characteristic length (ratio of volume to surface area) and thus the Biot number is much smaller for slender bodies 4-12 Relations are to be obtained for the characteristic lengths of a large plane wall of thickness 2L, a very long cylinder of radius ro and a sphere of radius ro Analysis Relations for the characteristic lengths of a large plane wall of thickness 2L, a very long cylinder of radius ro and a sphere of radius ro are Lc , wall = Lc ,cylinder = Lc , sphere = V Asurface V Asurface V Asurface = LA =L 2A = πro2 h ro = 2πro h = 4πro3 / 4πro = ro 2ro 2ro 4-13 A relation for the time period for a lumped system to reach the average temperature (Ti + T∞ ) / is to be obtained Analysis The relation for time period for a lumped system to reach the average temperature (Ti + T∞ ) / can be determined as T (t ) − T∞ = e −bt ⎯ ⎯→ Ti − T∞ Ti + T∞ − T∞ = e −bt Ti − T∞ Ti − T∞ = e −bt 2(Ti − T∞ ) − bt = − ln ⎯ ⎯→ t = b b PROPRIETARY MATERIAL © 2007 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

Ngày tải lên: 07/03/2018, 16:28

... decreases 1%, the heat transfer coefficient increase 0.65% and mass transfer coefficient increase 3.27% (figure 11) A correlation which gives the heat transfer coefficient and mass transfer coefficient ... Wijeysundera and J.C Ho Simplified models for coupled heat and mass transfer in falling- film absorbers, Int J of Heat and Mass Transfer. , vol 47(2), pp 395-406 2004 [3] Oosthuizen, Patric H and David ... Qa_sim 3.671 12.3 The heat transfer coefficient and mass transfer coefficient as functions of the initial solution concentration, solution mass flow rate per unit tube length, and cooling water temperature

Ngày tải lên: 30/06/2022, 09:06

... of heat and mass transfer coefficients The effects of the solution concentration, solution mass flow rate per unit tube length, and cooling water temperature to the heat transfer coefficient and ... phenomenon of coupled heat and mass transfer in steady state is described by the energy transport © 2020 114 AFFECTING PARAMETERS TO THE HEAT AND MASS TRANSFER OF NH3-H2O SOLUTION FALLING ON THE ... the heat transfer coefficient and mass transfer coefficient in the absorption © 2020 i h c Cơng nghi p Thành ph H Chí Minh AFFECTING PARAMETERS TO THE HEAT AND MASS TRANSFER OF NH3-H2O ` SOLUTION

Ngày tải lên: 25/10/2022, 11:14

... Solution Manual for Heat and Mass Transfer Fundamentals and Applications 5th Edition by Cengel https://getbooksolutions.com/download /solution- manual- for -heat- and- mass- transfer- fundamentalsand-applications-5th-edition -by- cengel ... 2-1 Solutions Manual for Heat and Mass Transfer: Fundamentals & Applications 5th Edition Yunus A Cengel & Afshin J Ghajar McGraw-Hill, 2015 Chapter HEAT CONDUCTION EQUATION Download Full Solution ... https://getbooksolutions.com/download /solution- manual- for -heat- and- mass- transfer- fundamentalsand-applications-5th-edition -by- cengel PROPRIETARY AND CONFIDENTIAL This Manual is the proprietary property of The McGraw-Hill Companies, Inc (“McGraw-Hill”) and protected by copyright and other state and federal laws By

Ngày tải lên: 28/02/2019, 14:49

... 2-1 Solutions Manual for Heat and Mass Transfer: Fundamentals & Applications 5th Edition Yunus A Cengel & Afshin J Ghajar McGraw-Hill, 2015 Chapter HEAT CONDUCTION EQUATION PROPRIETARY AND CONFIDENTIAL ... CONFIDENTIAL This Manual is the proprietary property of The McGraw-Hill Companies, Inc (“McGraw-Hill”) and protected by copyright and other state and federal laws By opening and using this Manual the ... conditions by cycling on and off Heat transfer into the refrigerated space is three-dimensional in nature since heat will be entering through all six sides of the refrigerator However, heat transfer

Ngày tải lên: 28/02/2019, 15:47

... Solution Manual for Heat and Mass Transfer 5th Edition by Cengel 1-1 Full file at https://TestbankDirect.eu/ Solutions Manual for Heat and Mass Transfer: Fundamentals & ... https://TestbankDirect.eu/ Solution Manual for Heat and Mass Transfer 5th Edition by Cengel 1-87 Full file at https://TestbankDirect.eu/ 1-148 Eggs with a mass of 0.15 kg per egg and a specific heat of 3.32 ... flux q It is related to the rate of heat transfer by Q   qdA A 1-14C Energy can be transferred by heat, work, and mass An energy transfer is heat transfer when its driving force is temperature

Ngày tải lên: 20/08/2020, 12:02

... convection heat transfer is expressed as Q& = hAs (Ts − T∞ ) Disregarding any heat transfer by radiation and thus assuming all the heat loss from the wire to occur by convection, the convection heat transfer ... Steady operating conditions exist Heat 55°C transfer by radiation is disregarded The convection heat transfer coefficient is constant and uniform over the surface Heat transfer from the base of the ... The rate of heat transfer from the air to the plate is to be determined Assumptions Steady operating conditions exist Heat transfer by radiation is not considered The convection heat transfer coefficient

Ngày tải lên: 07/03/2018, 16:28

... is losing heat to the surrounding air at 25°C by convection with a heat transfer coefficient of 12 W/m2⋅°C, and by radiation to the surrounding surfaces at 15°C The total rate of heat transfer ... conditions exist Heat transfer by convection is disregarded The emissivity of the box is constant and uniform over the exposed surface Heat transfer from the bottom surface of the box to the stand is negligible ... completely enclosed by the surrounding ε=0.9 surfaces, and he or she will lose heat to the surrounding air by Qconv convection and to the surrounding surfaces by radiation The total rate of heat loss from

Ngày tải lên: 07/03/2018, 16:28

... surface area is called heat flux q& It is related to the rate of heat transfer by Q& = ∫ q&dA A 1-9C Energy can be transferred by heat, work, and mass An energy transfer is heat transfer when its ... INTRODUCTION AND BASIC CONCEPTS Thermodynamics and Heat Transfer 1-1C Thermodynamics deals with the amount of heat transfer as a system undergoes a process from one equilibrium state to another Heat transfer, ... fixed amount of mass (no mass transfer) Under the stated assumptions, the energy balance on the system can be expressed as E −E 1in424out = Net energy transfer by heat, work, and mass ΔE system

Ngày tải lên: 07/03/2018, 16:28

... Assumptions Heat transfer is steady since there is no change with time Heat transfer is onedimensional since this two-layer heat transfer problem possesses symmetry about the center line and involves ... Thermal conductivity is constant Heat generation is uniform Analysis (a) Noting that the heat flux and the heat generated will be transferred to the water, the heat transfer coefficient is determined ... rate, the surface heat fluxes, and the relationship between these heat fluxes, the heat generation rate, and the geometry of the wall are to be determined Assumptions Heat transfer is steady

Ngày tải lên: 07/03/2018, 16:28

... differences (and thus heat transfer) will exist in the radial and axial directions (but there will be symmetry about the center line and no heat transfer in the azimuthal direction.) 2-9C Yes, the heat ... since temperature differences (and thus heat transfer) will exist in the radial and axial directions (but there will be symmetry about the center line and no heat transfer in the azimuthal direction ... direction of heat transfer) is constant, the rate of heat transfer along the rod is determined from T − T2 Q& = kA L T1=25°C Insulated D = 0.05 m T2=95°C where L = 0.15 m and the heat transfer area

Ngày tải lên: 07/03/2018, 16:28

... temperature and the rate of heat transfer through the shell are to be determined Assumptions Heat transfer is given to be steady and one-dimensional Thermal conductivity varies linearly There is no heat ... temperature T∞ , and heat transfer takes place between the body and its environment with a heat transfer coefficient h During a differential time interval dt, the temperature of the body rises by a differential ... transient two-dimensional heat transfer with no heat generation Assumptions Heat transfer is transient and two-dimensional Thermal conductivity is constant There is no heat generation Analysis

Ngày tải lên: 07/03/2018, 16:28

... convection heat transfer However, adding too many fins on a surface can suffocate the fluid and retard convection, and thus it may cause the overall heat transfer coefficient and heat transfer ... temperature, and its value is between and Fin effectiveness is defined as the ratio of heat transfer rate from a finned surface to the heat transfer rate from the same surface if there were no fins, and ... 3-99C Heat transfer rate will decrease since a fin effectiveness smaller than indicates that the fin acts as insulation 3-100C Fins enhance heat transfer from a surface by increasing heat transfer

Ngày tải lên: 07/03/2018, 16:28

... steady operation, heat transfer from the room to the roof (by convection and radiation) must be equal to the heat transfer from the roof to the surroundings (by convection and radiation), that ... Q& = hAs (Ts − T∞ ) In steady heat transfer, heat transfer rate to the wall and from the wall are equal Therefore at the outer surface which has convection heat transfer coefficient three times ... resistance to heat transfer through window, and thus the heat transfer rate will be smaller relative to the one which consists of a single mm thick glass sheet 3-14C Convection heat transfer through

Ngày tải lên: 07/03/2018, 16:28

... against each other 3-44C Heat transfer through the voids at an interface is by conduction and radiation Evacuating the interface eliminates heat transfer by conduction, and thus increases the thermal ... resistance of the wall and the rate of heat transfer through the wall are to be determined Assumptions Heat transfer is steady since there is no indication of change with time Heat transfer through ... indoor and outdoor temperatures, the rate of heat transfer from the kiln is to be determined Assumptions Heat transfer is steady since there is no indication of change with time Heat transfer

Ngày tải lên: 07/03/2018, 16:28

... subjected to convection and radiation heat transfer at its outer surface The rate of heat transfer and the amount of ice that melts per day are to be determined Assumptions Heat transfer is steady ... kg/m3 and cp = 4180 J/kg.°C Analysis This is a transient heat conduction, and the rate of heat transfer will decrease as the drink warms up and the temperature difference between the drink and ... kg/m3 and cp = 4180 J/kg.°C Analysis This is a transient heat conduction, and the rate of heat transfer will decrease as the drink warms up and the temperature difference between the drink and

Ngày tải lên: 07/03/2018, 16:28

... insulation are to be determined Assumptions Heat transfer is steady Heat transfer is one-dimensional The combined heat transfer coefficient is constant and uniform over the entire surface The temperature ... the pipe by 90 percent The amount of heat loss from the steam in 10 h and the amount of saved per year by insulating the steam pipe Assumptions Heat transfer through the pipe is steady and one-dimensional ... and 0.22-m-thick wall made of concrete (k = 1.1 W/m·ºC) The design temperatures of the indoor and outdoor air are 24ºC and 3ºC, respectively, and the heat transfer coefficients on the inner and

Ngày tải lên: 07/03/2018, 16:28

... of thermal and mass transfer boundary conditions can be encoun- tered in practice. Standard thermal and mass transfer boundary condition types are often used in theoretical models and experiments, ... (m) l ent,ma Mass transfer entrance length (m) l ent,th Thermal (heat transfer) entrance length (m) l M Turbulence mixing length ( m) l M, ma Turbulence mixing length f or mass transfer (m) l heat Heated ... (m) l th Turbulence mixing length f or heat transfer (m) M Molar mass (kg/kmol) Ma Mach number m Mass fraction; dimensionless constant m Mass (kg); mass of a single molecule (kg) m  Mass flux (kg/m 2 s) N Ratio...

Ngày tải lên: 30/03/2014, 19:20

... corresponds to that of heat conduction, whilst mass transfer in a flowing fluid, known for short as convective mass transfer corresponds to convective mass transfer. Mass transfer by diffusion and convection ... only sorts of mass transfer. Radiative heat transfer has no corresponding mass transfer process. 1.4.1 Diffusion The calculation of mass transfer by diffusion requires several definitions and rela- tionships ... time. Further important investigations included heat transfer in film condensation, cross current heat transfer and the analogy between heat and mass transfer in evaporation. 76 1 Introduction. Technical...

Ngày tải lên: 02/04/2014, 15:27

... Convection Heat and Mass Transfer 457 7.5 The Sphere 465 7.6 Flow Across Banks of Tubes 468 7.7 Impinging Jets 477 7.7.1 Hydrodynamic and Geometric Considerations 477 7.7.2 Convection Heat and Mass Transfer ... any case, if convection heat transfer will occur from the surface to the outer flow. The convection heat transfer mode is sustained both by random molecular motion and by the bulk motion of the ... the text and by practicing engineers. However, Section 8.7 Heat Transfer Enhance- ment, and Section 8.8 Flow in Small Channels may be viewed as optional. Buoyancy-induced flow and heat transfer...

Ngày tải lên: 02/04/2014, 15:51