Experimental and Numerical Analysis of a PCM-Supported ...

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Contents List of figures ............................................................................................................ viii List of Tables ............................................................................................................. xi List of Frames ............................................................................................................ xi 1 Introduction ............................................................................................................. 1 1.1 Fresh water challenges ..................................................................................... 1 1.2 Desalination option ........................................................................................... 2 1.3 Overview on desalination processes................................................................. 2 1.3.1 Energy requirements and water cost ...................................................... 4 1.3.2 Selection criteria of desalination technology ........................................... 5 1.3.3 Coupling desalination plants with power plants....................................... 6 1.3.4 Coupling renewable energies with desalination technologies ................. 6 1.3.5 Barriers and limitations of RE-desalination ............................................. 8 1.4 Solar desalination ............................................................................................. 9 1.4.1 Conventional solar stills .......................................................................... 9 1.4.2 Humidification-Dehumidification technique ........................................... 10 1.5 Aim of the work ............................................................................................... 11 1.6 Dissertation Overview ..................................................................................... 12 2 Literature Survey .................................................................................................. 13 2.1 Introduction ..................................................................................................... 13 2.2 Importance of solar energy storage ................................................................ 13 2.3 Thermo-Chemical Energy Storage.................................................................. 14 2.4 Sensible heat energy storage (SHES) ............................................................ 15 2.5 Latent heat energy storage (LHES) ................................................................ 15 2.5.1 Concept of Phase Change Energy Storage .......................................... 15 2.5.2 Advantages of LHES ............................................................................. 17 2.5.3 Solid-Solid Phase Change Storages ..................................................... 17 2.5.4 Solid-Liquid-Vapour Phase Change Storages....................................... 18 2.5.5 Solid-Liquid Phase Change Storages ................................................... 18 2.6 Classification of Phase Change Materials ....................................................... 19 2.6.1 Organic Phase Change Materials ......................................................... 20 2.6.2 Inorganic Phase Change Materials ....................................................... 21 2.6.3 Eutectics ............................................................................................... 22 2.6.4 Salt Mixtures ......................................................................................... 23 2.6.5 Multi Grade Phase Change Materials ................................................... 24 2.7 Heat transfer in PCM regenerators ................................................................. 25 2.8 Desalination with humidification-dehumidification technique .......................... 27 2.8.1 Classification of HDH systems .............................................................. 28 2.8.2 Principles of operation .......................................................................... 29 2.8.3 Lumped model analysis ........................................................................ 31 2.8.4 Review of Performance ........................................................................ 36 2.8.4.1 Effect of feed seawater mass flow rate .............................................. 36 2.8.4.2 Effect of air to water mass flow ratio .................................................. 39 iv
2.8.4.3 Effect of air heating ............................................................................ 40 2.8.4.4 Effect of packing height ...................................................................... 42 2.8.4.5 Type of carrier gas ............................................................................. 46 2.8.5 Air dehumidification ............................................................................... 46 2.8.6 Solar collectors ..................................................................................... 50 2.8.7 Thermal storage .................................................................................... 51 2.8.8 Summary of the literature on HDH systems .......................................... 53 2.8.9 Conclusion and spot light ...................................................................... 54 3 Scope of the Study ............................................................................................... 55 3.1 Scope of the study .......................................................................................... 55 3.2 Proposed system and operation cycle ............................................................ 55 3.3 Concept of Multi-Effects of Heating and Humidification (MEHH) .................... 57 3.3.1 Micro scale level ................................................................................... 57 3.3.2 Macro scale level .................................................................................. 59 3.4 Concept of Multi-Effects of Cooling and Condensation (MECC) ..................... 61 3.5 Study objectives and methodology ................................................................. 61 4 Theoretical Analysis and Modeling ....................................................................... 63 4.1 System variables............................................................................................. 63 4.2 Mathematical Modeling ................................................................................... 64 4.2.1 Model assumptions ............................................................................... 66 4.2.2 Flow in the external heat storage .......................................................... 68 4.2.3 Two phase flow in dual phase change regenerators ............................. 71 4.2.4 Closure relationships ............................................................................ 79 4.3 Hydrodynamic analysis ................................................................................... 87 4.3.1 Gas-liquid interaction ............................................................................ 87 4.3.2 Column Sizing ....................................................................................... 88 4.4 Modeling solid-liquid phase change ................................................................ 89 4.5 Macro-dynamic performance analysis of the HDH system ............................. 92 4.5.1 Cooling tower performance ................................................................... 92 4.5.2 Humidifier efficiency .............................................................................. 92 4.5.3 Dehumidifier efficiency .......................................................................... 93 4.5.4 Productivity factor (PF) .......................................................................... 95 4.5.5 Efficiency of the solar collector.............................................................. 95 4.5.6 Energy balance on heat exchangers..................................................... 96 4.5.7 Overall system performance ................................................................. 97 4.5.8 Salt and mass flow balances ................................................................ 98 4.6 Representation of the MEHH and MECD phenomena .................................... 99 4.6.1 Fundamental points .............................................................................. 99 4.6.2 Capturing the MEHH and MECD phenomena .................................... 100 5 Experimental Analysis ........................................................................................ 103 5.1 Experimental setup and procedures ............................................................. 103 5.1.1 Design objectives ................................................................................ 103 5.1.2 Experimental Facility ........................................................................... 104 5.2 Measuring Techniques .................................................................................. 105 v
Page 1: Technische Universität München In
Page 4 and 5: It is my pleasure to thank Prof. Th
Page 8 and 9: 5.3 Functional description ........
Page 10 and 11: List of Figures Figure 1.1: Cost br
Page 12 and 13: 78cm; Top: Evaporator, Bottom: Cond
Page 14 and 15: xii
Page 16 and 17: m Mass flow rate; [kg.s -1 ] m eva
Page 18 and 19: ed c coll cond cw d d e or eff evap
Page 20 and 21: 1 Introduction The first part of th
Page 22 and 23: summarized in figure (1.2). Thermal
Page 24 and 25: 1.3.2 Selection criteria of desalin
Page 26 and 27: of energy storage or hybridization
Page 28 and 29: Desalination development focuses on
Page 30 and 31: Introduction of the indirect type s
Page 32 and 33: 2 Literature Survey 2.1 Introductio
Page 34 and 35: There is actually a commercial prod
Page 36 and 37: Q m H c ( T T1) c ( T 2 T ) (2.2)
Page 38 and 39: (solid-liquid) have a storage densi
Page 40 and 41: (iii) a sharp melting temperature.
Page 42 and 43: melt and freeze without segregation
Page 44 and 45: However, the stored heat is less va
Page 46 and 47: parameters on the heat transfer and
Page 48 and 49: categories. The first category is b
Page 50 and 51: to 550 kWh/m 3 of distilled water a
Page 52 and 53: The enthalpy and humidity of the sa
Page 54 and 55: Air mass flow rate [kg/h] GOR [-] 1
Page 56 and 57:
On the other hand, the efficiency o
Page 58 and 59:
2.8.4.2 Effect of air to water mass
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distillate rate. The system was not
Page 62 and 63:
were; EnviPac Gr.1, 32 mm, and VFF
Page 64 and 65:
Figure 2.15: Height versus air temp
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The performance of the condenser is
Page 68 and 69:
Klausner and Mei [136] described a
Page 70 and 71:
The impact of the collector cost ca
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exchanger and energy storage in one
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3 Scope of the Study This chapter p
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packing where it gets in direct con
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In fact there is a tradeoff between
Page 80 and 81:
The energy flow between all and eac
Page 82 and 83:
4 Theoretical Analysis and Modeling
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The two-energy equation models whic
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solid-liquid phase change inside th
Page 88 and 89:
assumed by conduction in both axial
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the air pressure drop ∆P per unit
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evaporation rate per unit volume of
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where β t , β c , ρ ref , c ref
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the viscous transport and introduce
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liquid and solid phases, respective
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4.2.3.3 Liquid and gas hold-ups Liq
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Several models and approaches for m
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where G=ρU d /ε g is the pore mas
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k k eff s 1 3 2 (4.55) This cor
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uncertainties associated with the f
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1 2 (4.62) d1 capp c2 c1 c2 1
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[58] evaluated the cooling tower ai
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1 exp NTU 1 C r, cond cond (4
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A HE QHE U T HE LM (4.81) Where Q
Page 118 and 119:
c M f b (4.86) M b S S f where r
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that form the study logical foundat
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5 Experimental Analysis This chapte
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5.2 Measuring Techniques K-type the
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The product condensed water was mea
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operating limits. In light of the l
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In the last two cases, the inlet ho
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performance and its threshold value
Page 134 and 135:
It could be interpreted that this p
Page 136 and 137:
Evaporator Condenser Figure 5.8: Av
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within the inaccuracy margins. The
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The last two cases of boundary cond
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natural air flow in the system. In
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6 Model Implementation and Validati
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x t u x u 0 0 , (6.5) and for a s
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Next time step validation were the
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The evaporator and condenser both w
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Figure 6.2: Evolution of inlet and
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Figure 6.4: Evolution of inlet and
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temperature is at its maximum level
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Bottom Top Figure 6.7: Evolution of
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7 Parameters Analysis of the Evapor
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Figure 7.1: Effect of packing size
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e 0.45 kPa under natural convection
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aspect ratio under constant bed vol
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Figure 7.7: Effect of inlet hot wat
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well as the time required to reach
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Figure 7.10: Effect of packing medi
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40°C respectively. This gives flex
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the condensate rate, productivity f
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esult, rather than PCM media which
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Figure 7.18: Effect of PCM thermal
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8 Optimization of HDH plant In this
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The MATLAB model describes how the
Page 186 and 187:
less steep than that of the distill
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8.3.4 Effect of hot water flow rate
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storage materials and thus it can h
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for latent heat storage would be ob
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When T m becomes sufficiently highe
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9 Summary and conclusions 9.1 Summa
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productivities at any cooling water
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[13] Vafai K., Sozen M. An investig
Page 202 and 203:
[48] Crone S., Bergins C., and Stra
Page 204 and 205:
[79] Tiwari G.N. and Yadav Y.P. (78
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[109] Mehling H., Hiebler S. and Zi
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[139] Belessiotis V, Delyannis E (2
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Appendices Appendix A A1. PCM Therm
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A3. Constants and Thermo-physical p
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From the above correlation, the con
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The Ergun analogy factor J h repres
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Equation (C.7) represents an overal
Page 220 and 221:
Appendix D D1. Cooling tower theory
Page 222 and 223:
A m w = the plan or cross sectiona
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