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Heat and Mass Transfer

, Volume 55, Issue 8, pp 2305–2328 | Cite as

Local wall heat transfer coefficient measurement in a packed bed of cylinders using infrared (IR) thermography technique and application of random packing of cylindrical particles inside concentric tube heat exchangers with water as working medium

  • Surfarazhussain S. Halkarni
  • Arunkumar Sridharan
  • S. V. PrabhuEmail author
Original
  • 103 Downloads

Abstract

Heat transfer enhancement is challenging area in which different techniques are utilized to dissipate the generated heat during operation. Packed beds are devices which enhance heat transport while being compact and are used in several applications such as energy storage, heat exchange devices, catalysis, food processing etc. In the present study, the behavior of wall heat transfer coefficient with randomized packing of equal aspect ratio cylinders is investigated. In this work, the local wall heat transfer coefficient is calculated from local wall temperature data obtained using infrared (IR) thermography in packed beds with randomized packing of cylinders under steady state conditions with water as the working fluid. The randomized packing of cylinders is done inside a concentric tube heat exchanger and the heat transfer enhancement is studied. Experiments are conducted for bed to equivalent particle diameter ratio 2 using random packing of mono-dispersed glass cylinders (dcyl = 6 mm and lcyl = 6 mm). The local wall temperatures are measured using an infrared (IR) camera while the fluid flow takes place through the packed beds. In literature, it is found that wall region contribution to heat transfer is above 90%. The comparison of enhancement in heat transfer for both packing of spheres and cylinders inside concentric tube heat exchangers is done and it is observed that the random sphere packing is superior to cylinder packing.

Keywords

Wall heat transfer coefficient Void fraction Packed bed of cylinders packed bed of spheres Infrared (IR) thermography 

Nomenclature

Symbol

A

Heat transfer area for heat exchanger (mm2)

Cpf

Specific heat capacity of fluid (Jkg−1 K−1)

D

Bed diameter or Inner diameter of tube (mm)

Di

Inner diameter of annular side pipe (mm)

Da

Annulus diameter (mm)

deq.p

Equivalent particle diameter (mm)

dh

Annulus hydraulic diameter (mm)

dp

Particle diameter (mm)

dcyl

Diameter of cylinder (mm)

f

Comparable friction factor (dimensionless)

fs

Friction factor for open smooth pipe (dimensionless)

lcyl

Length of cylinder (mm)

hw

Wall heat transfer coefficient (W m−2 K−1)

hi

Inner side wall heat transfer coefficient (Tube side) (W m−2 K−1)

ho

Outer side wall heat transfer coefficient (Annular side) (W m−2 K−1)

kf

Thermal conductivity of fluid (W m−1 K−1)

kpipe

Thermal conductivity of tube wall (W m−1 K−1)

ks

Thermal conductivity of solid (W m−1 K−1)

L

Length of packed bed (mm)

Lh

Heating length (mm)

Mass flow rate (kg s−1)

h

Mass flow rate of hot fluid (kg s−1)

c

Mass flow rate of cold fluid (kg s−1)

Nua

Nusselt number with augmentation (dimensionless)

Nuc

Nusselt number for the case of constant pumping power (dimensionless)

Nus

Nusselt number for the case of same Reynolds number (Gnieleinski’s correlation) (dimensionless)

Nuw

Nusselt number at wall based on particle diameter, \( \frac{h_w{d}_p}{k_f} \) (dimensionless)

Nui

Nusselt number on inner side (heat exchangers) (dimensionless)

Nuo

Nusselt number on outer side (heat exchangers) (dimensionless)

Nuh

Nusselt number based on hydraulic diameter for annular side packing (dimensionless)

\( {q}_w^{{\prime\prime} } \)

Heat flux (W m−2)

\( {\overset{.}{q}}_w \)

Heat generation per unit volume (W m−3)

Re

Reynolds number based on bed diameter, \( \frac{\rho\;U\;D}{\mu } \) (dimensionless)

Rep

Reynolds number based on particle diameter, \( \frac{\rho\;U\;{d}_p}{\mu } \) (dimensionless)

Rea

Reynolds number based on annulus diameter, \( \frac{\rho\;{V}_c\;{D}_a}{\mu } \) (dimensionless)

Reh

Reynolds number based on hydraulic diameter, \( \frac{\rho\;{V}_c\;{d}_e}{\mu } \) (dimensionless)

Reo

Equivalent Reynolds number (defined in Appendix 1) (dimensionless)

SB

Particle surface area per unit volume of packed bed (m−1)

Tamb

Ambient fluid temperature (surrounding air of test section) (°C)

Tbf

Bulk fluid temperature (°C)

Tfi

Inlet fluid temperature (upstream test section) (°C)

Tfo

Exit fluid temperature (downstream test section) (°C)

Tm

Mixing cup fluid temperature (measuring tank) (°C)

Two

Outer wall temperature (test section) (°C)

Twi

Inner wall temperature (test section) (°C)

Thi

Inlet fluid temperature in hot line (PBHE) (°C)

Tho

Exit fluid temperature in hot line (PBHE) (°C)

Tci

Inlet fluid temperature in cold line (PBHE) (°C)

Tco

Exit fluid temperature in cold line (PBHE) (°C)

∆Tlm

Logarithmic mean temperature difference (PBHE) (°C)

U

Superficial velocity (based on bed cross-sectional area) (m s−1)

Upbhe

Overall heat transfer coefficient for packed bed heat exchanger (PBHE) (W m−2 K−1)

Vh

Hot fluid velocity (PBHE) (m s−1)

Vc

Cold fluid velocity (PBHE) (m s−1)

Vvoid

Interstitial volume of packed bed (mm3)

Greek symbols

ε

Void fraction (mean) (dimensionless)

εpaint

Emissivity of paint used for infrared thermography (dimensionless)

εt

Void fraction (mean) tube side (dimensionless)

εa

Void fraction (mean) annular side (dimensionless)

μ

Dynamic Viscosity (Pa. s)

ρ

Density (kg m−3)

Abbreviation

PBHE

Packed Bed Heat Exchanger

Notes

Acknowledgements

Authors would like to thank Mr. Rahul Shirsat for his assistance in building the experimental setup.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Surfarazhussain S. Halkarni
    • 1
    • 2
  • Arunkumar Sridharan
    • 1
  • S. V. Prabhu
    • 1
    Email author
  1. 1.Fluid Mechanics and Fluid Power Laboratory, Department of Mechanical EngineeringIndian Institute of Technology BombayMumbaiIndia
  2. 2.Department of Mechanical Engineering, School of Engineering & Applied SciencesSRM University AmaravatiGunturIndia

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