Heat Exchangers-Introduction

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Heat Exchangers-Introduction

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Heat Exchangers-Introduction

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers--Types

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers-Types

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Heat Exchangers-Overall Heat Transfer Coefficient (U)

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Heat Exchangers-Overall Heat Transfer Coefficient (U)

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Heat Exchangers-Overall Heat Transfer Coefficient (U)

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Heat Exchangers-Overall Heat Transfer Coefficient (U)

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Heat Exchangers-Fouling Factor (Rf)

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Heat Exchangers-Fouling Factor (Rf)

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Heat Exchangers-Overall Heat Transfer Coefficient (U)

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Fouling factors must be obtained experimentally by determining the values of U for

both clean and dirty conditions in the heat exchanger. The fouling factor is thus

defined as

Heat Exchangers-Fouling Factor (Rf)

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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The above derivation for LMTD involves two important assumptions:

(1) the fluid specific heats do not vary with temperature, and (2) the

convection heat-transfer coefficients are constant throughout the heat

exchanger. The second assumption is usually the more

serious one because of entrance effects, fluid viscosity, and thermal-

conductivity changes, etc. Numerical methods must normally be

employed to correct for these effects. If a heat exchanger other than the

double-pipe type is used, the heat transfer is calculated by using a

correction factor applied to the LMTD for a counter flow double-pipe

arrangement with the same hot and cold fluid temperatures.

Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-LMTD

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Heat Exchangers-NTU

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Heat Exchangers-NTU

The LMTD approach to heat-exchanger analysis is useful when the inlet and

outlet temperatures are known or are easily determined. The LMTD is then easily

calculated, and the heat flow, surface area, or overall heat-transfer coefficient may

be determined. When the inlet or exit temperatures are to be evaluated for a given

heat exchanger, the analysis frequently involves an iterative procedure because of

the logarithmic function in the LMTD. In these cases the analysis is performed

more easily by utilizing a method based on the effectiveness of the heat

exchanger in transferring a given amount of heat. The effectiveness method also

offers many advantages for analysis of problems in which a comparison between

various types of heat exchangers must be made for purposes of selecting the type

best suited to accomplish a particular heat-transfer objective.

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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Heat Exchangers-NTU

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