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Heat and Mass Transfer

, Volume 55, Issue 1, pp 81–93 | Cite as

Experimental investigation of the heat and mass transfer in a tube bundle absorber of an absorption chiller

  • Michael OlbrichtEmail author
  • Andrea Luke
Original
  • 78 Downloads

Abstract

The design of the absorber of absorption chillers is still subject to great uncertainty since the coupled processes of heat and mass transfer as well as the influence of systemic interactions on the absorption process are not fully understood. Unfortunately, only a few investigations on the transport phenomena in the absorber during operation in an absorption chiller are reported in the literature. Therefore, experimental investigations on the heat and mass transfer during falling film absorption of steam in aqueous LiBr-solution are carried out in an absorber installed in an absorption chiller in this work. An improvement of heat and mass transfer due to the increase in convective effects are observed as the Ref number increases. Furthermore, an improvement of the heat transfer in the absorber with increasing coolant temperature can be identified in the systemic context. This is explained by a corresponding reduction in the average viscosity of the solution in the absorber. A comparison with experimental data from literature obtained from so-called absorber-generator test rigs shows a good consistency. Thus, it has been shown that the findings obtained on these simplified experimental setups can be transferred to the absorber in an absorption chiller. However, a comparison with correlations from the literature reveals a strong deviation between experimental and calculated results. Hence, further research activities on the development of better correlations are required in future.

Nomenclature

Latin symbols

A

Area (m2)

cp

Specific heat capacity (kJ/kgK)

Cpc

Compactness factor (−)

d

Diameter of tube(m)

D

Diffusion coefficient (m2/s)

g

Gravitational acceleration (m/s2)

j

Number of parallel tube columns

k

Overall heat transfer coefficient (W/m2K)

l

Length of tube (m)

L

Inter tube distance in the bundle (m)

\( \dot{\mathrm{m}} \)

Mass flow rate(kg/s)

p

Pressure (bar)

\( \dot{\mathrm{q}} \)

Heat flux (W/m2)

\( \dot{\mathrm{Q}} \)

Rate of heat flow (W)

R

Radius (m)

T

Temperature (°C)

x

Mass related concentration (mass fraction kgLiBr/kgsolution) (%)

Dimensionless parameters

Nu

Nusselt number (−)

Pr

Prandtl number(−)

Re

Reynolds number (−)

Ref

Film Reynolds number (−)

Sc

Schmidt number (−)

Sh

Sherwood number (−)

Greek symbols

α

Heat transfer coefficient (W/m2K)

β

Mass transfer coefficient (m/s)

Γ

Mass flow rate per tube length and side (kg/m·s)

ε

Roughness (m)

η

Dynamic viscosity (Pa s)

λ

Heat conduction (W/m)

ν

Kinetic viscosity (m2/s)

ρ

Density (kg/m3)

ξ

Friction factor

Subscripts

0

Reference

c

Coolant

coolant

Cooling water

cold

Cold water

crit

Critical

Cu

Copper

exp

Experimental

f

Film

h

Horizontal

H2O

Water

hot

Hot water

i

Inner / inlet

L

Liquid

LiBr

Lithium bromide

lm

Logarithmic mean

o

Outer / outlet

p

Parallel

pred

Predicted

poor

Poor solution

ref

Refrigerant

rich

Rich solution

s

Solution

st

Steam

sv

Symmetric vertical

svref

Symmetric vertical reference

Superscripts

eq

Equilibrium

Notes

Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Institute of Technical ThermodynamicsUniversity of KasselKasselGermany

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