The underlying concept of the standard effectiveness-number of transfer units (NTU) model is that the effectiveness of an exchanger can be correlated to two dimensionless parameters, namely, heat capacity ratio (Cr) and NTU. However, a limitation of this model is that it cannot account for the changes in effectiveness due to changes in operating temperature and humidity of simultaneous heat and moisture exchangers, specifically liquid-to-air membrane energy exchangers (LAMEEs). The purpose of this paper is to explain the reason for this limitation and also to explore the extension of the aforementioned concept of the effectiveness-NTU model to LAMEEs. The first contribution of this paper is to demonstrate that the reason for this limitation is that one of the simplifying assumptions of the standard effectiveness-NTU model, i.e., that Cr represents the ratio between the changes in the temperatures of the two fluid streams across an exchanger, is not applicable to LAMEEs. Further analysis in this paper yields two new fundamental dimensionless parameters that are analogous to Cr, termed effective Cr and effective m*, which represent the actual ratios between the changes in the temperatures and humidity ratios of the fluid streams. Then, it is shown that models analogous to the standard effectiveness-NTU model can be used to correlate the dependency of the effectiveness of LAMEEs on the operating temperature and humidity to effective Cr and effective m*.

References

References
1.
Field
,
C. B.
,
Barros
,
V. R.
,
Dokken
,
D.
,
Mach
,
K. J.
,
Mastrandrea
,
M. D.
,
Bilir
,
T. E.
,
Chatterjee
,
M.
,
Ebi
,
K. L.
,
Estrada
,
Y. O.
,
Genova
,
R. C.
,
Girma
,
B.
,
Kissel
,
E. S.
,
Levy
,
A. N.
,
MacCracken
,
S.
,
Mastrandrea
,
P. R.
, and
White
,
L. L.
,
2014
,
Climate Change 2014: Impacts, Adaptation, and Vulnerability—IPCC Working Group II Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change
,
Cambridge University Press.
Cambridge, UK
.
2.
ASHRAE
,
2007
,
Air Conditioning System Design Manual
,
2nd ed.
,
Butterworth-Heinemann
,
Burlington, MA
.
3.
Daou
,
K.
,
Wang
,
R.
, and
Xia
,
Z.
,
2006
, “
Desiccant Cooling Air Conditioning: A Review
,”
Renewable Sustainable Energy Rev.
,
10
(
2
), pp.
55
77
.
4.
Abdel-Salam
,
A. H.
,
Ge
,
G.
, and
Simonson
,
C. J.
,
2013
, “
Performance Analysis of a Membrane Liquid Desiccant Air-Conditioning System
,”
Energy Build.
,
62
, pp.
559
569
.
5.
Moghaddam
,
D. G.
,
LePoudre
,
P.
,
Ge
,
G.
,
Besant
,
R. W.
, and
Simonson
,
C.
,
2013
, “
Small-Scale Single-Panel Liquid-to-Air Membrane Energy Exchanger (LAMEE) Test Facility Development, Commissioning and Evaluating the Steady-State Performance
,”
Energy Build.
,
66
, pp.
424
436
.
6.
Namvar
,
R.
,
Pyra
,
D.
,
Ge
,
G.
,
Simonson
,
C. J.
, and
Besant
,
R. W.
,
2012
, “
Transient Characteristics of a Liquid-to-Air Membrane Energy Exchanger (LAMEE) Experimental Data With Correlations
,”
Int. J. Heat Mass Transfer
,
55
(
23–24
), pp.
6682
6694
.
7.
ASHRAE
,
2013
, “
Method of Testing Air-to-Air Heat/Energy Exchangers (ANSI Approved)
,”
American Society of Heating, Refrigerating and Air-Conditioning Engineers
, Atlanta, GA, Standard No. ANSI/ASHRAE Standard 84-2013.
8.
Ge
,
G.
,
Moghaddam
,
D. G.
,
Abdel-Salam
,
A. H.
,
Besant
,
R. W.
, and
Simonson
,
C. J.
,
2014
, “
Comparison of Experimental Data and a Model for Heat and Mass Transfer Performance of a Liquid-to-Air Membrane Energy Exchanger (LAMEE) When Used for Air Dehumidification and Salt Solution Regeneration
,”
Int. J. Heat Mass Transfer
,
68
, pp.
119
131
.
9.
Moghaddam
,
D. G.
,
LePoudre
,
P.
,
Besant
,
R. W.
, and
Simonson
,
C.
,
2013
, “
Steady-State Performance of a Small-Scale Liquid-to-Air Membrane Energy Exchanger for Different Heat and Mass Transfer Directions, and Liquid Desiccant Types and Concentrations: Experimental and Numerical Data
,”
ASME J. Heat Transfer
,
135
(
12
), p.
122002
.
10.
Seyed-Ahmadi
,
M.
,
Erb
,
B.
,
Carey
,
S. J.
, and
Besant
,
R. W.
,
2009
, “
Transient Behavior of Run-Around Heat and Moisture Exchanger System. Part І: Model Formulation and Verification
,”
Int. J. Heat Mass Transfer
,
52
(
25–26
), pp.
6000
6011
.
11.
Akbari
,
S.
,
Hemingson
,
H. B.
,
Beriault
,
D.
,
Simonson
,
C. J.
, and
Besant
,
R. W.
,
2012
, “
Application of Neural Networks to Predict the Steady State Performance of a Run-Around Membrane Energy Exchanger
,”
Int. J. Heat Mass Transfer
,
55
(
5–6
), pp.
1628
1641
.
12.
Zhang
,
L. Z.
,
2011
, “
An Analytical Solution to Heat and Mass Transfer in Hollow Fiber Membrane Contactors for Liquid Desiccant Air Dehumidification
,”
ASME J. Heat Transfer
,
133
(
9
), p.
092001
.
13.
Incropera
,
F.
, and
DeWitt
,
D.
,
1985
,
Fundamental of Heat and Mass Transfer
,
2nd ed.
,
Wiley
,
New York
.
14.
Simonson
,
C. J.
, and
Besant
,
R. W.
,
1999
, “
Energy Wheel Effectiveness: Part I—Development of Dimensionless Groups
,”
Int. J. Heat Mass Transfer
,
42
(
12
), pp.
2161
2170
.
15.
Simonson
,
C. J.
, and
Besant
,
R. W.
,
1999
, “
Energy Wheel Effectiveness: Part II—Correlations
,”
Int. J. Heat Mass Transfer
,
12
(
42
), pp.
2171
2185
.
16.
Zhang
,
L. Z.
, and
Niu
,
J. L.
,
2002
, “
Effectiveness Correlations for Heat and Moisture Transfer Processes in an Enthalpy Exchanger With Membrane Cores
,”
ASME J. Heat Transfer
,
124
(
5
), pp.
922
929
.
17.
Jaber
,
H.
, and
Webb
,
R. L.
,
1989
, “
Design of Cooling Towers by the Effectiveness-NTU Method
,”
ASME J. Heat Transfer
,
111
(
4
), pp.
837
843
.
18.
ASHRAE
,
2013
,
ASHRAE Handbook—Fundamentals
,
American Society of Heating, Refrigerating and Air-Conditioning Engineers
,
Atlanta, GA
.
19.
Narayan
,
G. P.
,
Mistry
,
K. H.
,
Sharqawy
,
M. H.
,
Zubair
,
S. M.
, and
Lienhard
,
J. H.
, V,
2010
, “
Energy Effectiveness of Simultaneous Heat and Mass Exchange Devices
,”
Front. Heat Mass Transfer
,
1
(
2
), pp.
1
13
.
20.
Moghaddam
,
D. G.
,
Oghabi
,
A.
,
Ge
,
G.
,
Besant
,
R. W.
, and
Simonson
,
C. J.
,
2013
, “
Numerical Model of a Small-Scale Liquid-to-Air Membrane Energy Exchanger: Parametric Study of Membrane Resistance and Air Side Convective Heat Transfer Coefficient
,”
Appl. Therm. Eng.
,
61
(
2
), pp.
245
258
.
21.
Shah
,
R. K.
, and
Sekulic
,
D. P.
,
2003
,
Fundamentals of Heat Exchanger Design
,
Wiley
,
Hoboken, NJ
.
22.
Conde
,
M.
,
2004
, “
Properties of Aqueous Solutions of Lithium and Calcium Chlorides: Formulations for Use in Air Conditioning Equipment Design
,”
Int. J. Therm. Sci.
,
43
(
4
), pp.
367
382
.
23.
Zaytsev
,
I. D.
, and
Aseyev
,
G.
,
1992
,
Properties of Aqueous Solutions of Electrolytes
,
CRC Press
,
Boca Raton, FL
.
24.
Zhang
,
L. Z.
,
Huang
,
S. M.
,
Chi
,
J. H.
, and
Peia
,
L. X.
,
2012
, “
Conjugate Heat and Mass Transfer in a Hollow Fiber Membrane Module for Liquid Desiccant Air Dehumidification: A Free Surface Model Approach
,”
Int. J. Heat Mass Transfer
,
55
(
13–14
), pp.
3789
3799
.
25.
Huang
,
S. M.
,
Zhang
,
L. Z.
,
Tang
,
K.
, and
Peia
,
L. X.
,
2012
, “
Fluid Flow and Heat Mass Transfer in Membrane Parallel-Plates Channels Used for Liquid Desiccant Air Dehumidification
,”
Int. J. Heat Mass Transfer
,
55
(
9–10
), pp.
2571
2580
.
26.
Cisternas
,
L. A.
, and
Lam
,
E. J.
,
1991
, “
Analytic Correlation for the Vapour Pressure of Aqueous and Non-Aqueous Solutions of Single and Mixed Electrolytes. Part II. Application and Extension
,”
Fluid Phase Equilib.
,
62
(
1
), pp.
11
27
.
27.
Oghabi
,
A.
,
Moghaddam
,
D. G.
,
Simonson
,
C. J.
, and
Besant
,
R. W.
,
2013
, “
Measurement of Heat Transfer Enhancement and Pressure Drop Across Eddy Promoter Air Screens in a Liquid-to-Air-Membrane Energy Exchanger (LAMEE)
,”
ASME
Paper No. HT2013-17252.
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