Advertisement

Heat and Mass Transfer

, Volume 46, Issue 4, pp 381–394 | Cite as

Counterflow, crossflow and cocurrent flow heat transfer in heat exchangers: analytical solution based on transfer units

  • Joel Charles BradleyEmail author
Original

Abstract

By means of analysis equations for heat transfer performance based on number of heat transfer units were found, that allow to solve in a simple way single-pass and multipass heat exchanger problems when there are counterflow, crossflow and cocurrent modes of flow in any combination. There is no need to use external information such as the effectiveness concept or the correction factor F. The analysis gives new results which are at variance with traditional heat exchanger analysis when crossflow or cocurrent flow is involved.

Keywords

Heat Transfer Heat Exchanger Transfer Unit Heat Transfer Area Cocurrent Flow 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

A

Overall heat transfer area

Acc

Heat transfer area where the mode of flow is counterflow

Acf

Heat transfer area where the mode of flow is crossflow

Acoc

Heat transfer area where the mode of flow is cocurrent

Cpc

Specific heat of cold stream, energy/mass–temperature difference

Cph

Specific heat of hot stream, energy/mass–temperature difference

F

Correction factor for the counterflow logarithmic mean temperature difference

mc

Main cold stream, mass flow into the heat echanger (mass/time)

mh

Main hot stream. mass flow into the heat echanger (mass/time)

mc

Main cold stream, mass flow per unit area, mass/area–time

mh

Main hot stream, mass flow per unit area, mass/area–time

msccc

Cold stream, mass flow in a counterflow section (mass/time)

mscch

Hot stream, mass flow in a counterflow section (mass/time)

mscfc

Cold stream, mass flow in a crossflow section (mass/time)

mscfh

Hot stream, mass flow in a crossflow section (mass/time)

mscocc

Cold stream, mass flow in a cocurrent flow section (mass/time)

mscoch

Hot stream, mass flow in a cocurrent flow section (mass/time)

NHTUA

Number of heat transfer units available

NHTUR

Number of heat transfer units required

Q

Heat load, energy/time

Tc

Cold stream temperature in the exchanger, average over the axis x at a point in the axis y for crossflow. For counterflow and cocurrent flow average in the axis transversal to flow at a point in the axis parallel to flow

Tc0

Average inlet cold stream temperature

Tc1

Average outlet cold stream temperature

Tc loc

Local cold stream temperature

Th

Hot stream temperature in the exchanger, average over the axis x at a point in the axis y for crossflow. For counterflow and cocurrent flow average in the axis transversal to flow at a point in the axis parallel to flow

Th0

Average outlet hot stream temperature

Th1

Average inlet hot stream temperature

Th loc

Local hot stream temperature

Ua

Volumetric overall heat transfer coefficient, energy/time–volume–temperature difference

U

Overall heat transfer coefficient, energy/time–area–temperature difference

Ucc

Overall heat transfer coefficient in a counterflow section

Ucf

Overall heat transfer coefficient in a crossflow section

Ucoc

Overall heat transfer coefficient in a cocurrent flow section

x

Dimension in the direction of m c flow in crossflow

y

Dimension in the direction of m h flow in crossflow

z

Dimension of the active volume, perpendicular to y and x

Δx

Length of stream m c flow path in a cross-flow stage

Δy

Length of stream m h flow path in a cross-flow stage or in counter or cocurrent flow

References

  1. 1.
    Bradley JC (2007) Single-stage and multistage mass transfer: simple rate-based analytical solution. Chem Eng Commun 194:4, 417–440Google Scholar
  2. 2.
    Kern DQ (1950) Process heat transfer. McGraw-Hill, New YorkGoogle Scholar
  3. 3.
    Bowman RA, Mueller AC, Nagel WM (1940) Mean temperature difference in design. Trans ASME 62:283–294Google Scholar
  4. 4.
    Fakheri A (2003) A general expression for the determination of the log mean temperature correction factor for shell and tube heat exchangers. J Heat Transf 125(3):527–530Google Scholar
  5. 5.
    TEMA (2007) Standards of Tubular Exchangers Manufacturers Association, 9th edn. TEMA, New YorkGoogle Scholar
  6. 6.
    (1999) Perry’s chemical engineers’ handbook, 7th edn. McGraw-Hill, New YorkGoogle Scholar
  7. 7.
    Incropera FP, DeWitt DP, Bergman TL, Lavine AS (2006) Fundamentals of heat and mass transfer, 6th edn. Wiley, New YorkGoogle Scholar

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.SaltilloMexico

Personalised recommendations