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

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40°C respectively. This gives flexibility in optimization of the system operation conditions depending on the site specific conditions with respect to the prevailing climatic conditions and seasonal variations of local cooling feed water source. Figure 7.12: Effect of inlet cooling water temperature on the condensation rate 7.3.2 Effect of inlet saturated air temperature Assuming saturation conditions (valid assumption for closed air loop cycles), increasing inlet air temperature will, of course, result in a higher water vapor content per kg of dry air and will increase the temperature and vapor pressure differences between the gas phase on one side and both PCM and liquid phases on the other side (i.e. increasing heat and mass transfer potentials). Therefore, the inlet air temperature is a very important parameter for the condenser performance. Figure (7.13) depicts the effect of inlet saturated air temperature on the hourly condensation rate. It seems that the condensation rate approximately varies linearly with the inlet air temperature at very low mass flow rate of cooling water and higher range of inlet air temperatures beyond 65-70°C regardless of the mass flow rate. The higher the cooling water mass flow rate, the stronger effect of the inlet air temperature is. While the inlet hot air is the heat source, increasing its sensible and latent heat capacities, the heat sink capacity should be enhanced with the same magnitude to meet the 155
condensation load. Increasing the mass flow rate of cooling water perhaps could be the easiest way to provide such extra heat sink capacity. Nevertheless, the outlet cooling water temperature will decrease, which certainly would have a negative impact on the effectiveness of heat recovery down stream of the condenser as was described in figure (4.1). Figure 7.13: Effect of inlet air temperature on the condensation rate From figure (7.13), it can be seen that to handle a specific condenser load, different combinations of inlet air temperature and matched cooling water mass flow rate can be applied under given boundary conditions. However, to get more insight into the effect of the ratio between source and sink heat flow capacities, the cooling water to air mass flow rate ratio has to be carefully studied as a crucial operational parameter. 7.3.3 Effect of cooling water to air mass flow ratio The ratio between cooling water to air mass flow rate is widely expressed in terms of liquid flux and gas fluxes (i.e. L/G ratio) to exclude the effect of column cross sectional area. To perform this analysis, the air superficial velocity was varied from 0.1 to 2m/s while the cooling water mass rate was varied from 250 to 1500l/h. The variations of air to water mass flow rate ratio and the cumulative hourly condensate are shown in figure (7.14) and figure (7.15). It can be realized from these figures that 156
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Technische Universität München In
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It is my pleasure to thank Prof. Th
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Contents List of figures ..........
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5.3 Functional description ........
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List of Figures Figure 1.1: Cost br
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78cm; Top: Evaporator, Bottom: Cond
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xii
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m Mass flow rate; [kg.s -1 ] m eva
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ed c coll cond cw d d e or eff evap
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1 Introduction The first part of th
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summarized in figure (1.2). Thermal
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1.3.2 Selection criteria of desalin
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of energy storage or hybridization
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Desalination development focuses on
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Introduction of the indirect type s
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2 Literature Survey 2.1 Introductio
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There is actually a commercial prod
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Q m H c ( T T1) c ( T 2 T ) (2.2)
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(solid-liquid) have a storage densi
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(iii) a sharp melting temperature.
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melt and freeze without segregation
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However, the stored heat is less va
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parameters on the heat transfer and
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categories. The first category is b
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to 550 kWh/m 3 of distilled water a
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The enthalpy and humidity of the sa
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Air mass flow rate [kg/h] GOR [-] 1
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On the other hand, the efficiency o
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2.8.4.2 Effect of air to water mass
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distillate rate. The system was not
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were; EnviPac Gr.1, 32 mm, and VFF
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Figure 2.15: Height versus air temp
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The performance of the condenser is
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Klausner and Mei [136] described a
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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
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The energy flow between all and eac
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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
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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
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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
Page 124 and 125: 5.2 Measuring Techniques K-type the
Page 126 and 127: The product condensed water was mea
Page 128 and 129: operating limits. In light of the l
Page 130 and 131: In the last two cases, the inlet ho
Page 132 and 133: 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
Page 138 and 139: within the inaccuracy margins. The
Page 140 and 141: The last two cases of boundary cond
Page 142 and 143: natural air flow in the system. In
Page 144 and 145: 6 Model Implementation and Validati
Page 146 and 147: x t u x u 0 0 , (6.5) and for a s
Page 148 and 149: Next time step validation were the
Page 150 and 151: The evaporator and condenser both w
Page 152 and 153: Figure 6.2: Evolution of inlet and
Page 154 and 155: Figure 6.4: Evolution of inlet and
Page 156 and 157: temperature is at its maximum level
Page 158 and 159: Bottom Top Figure 6.7: Evolution of
Page 160 and 161: 7 Parameters Analysis of the Evapor
Page 162 and 163: Figure 7.1: Effect of packing size
Page 164 and 165: e 0.45 kPa under natural convection
Page 166 and 167: aspect ratio under constant bed vol
Page 168 and 169: Figure 7.7: Effect of inlet hot wat
Page 170 and 171: well as the time required to reach
Page 172 and 173: Figure 7.10: Effect of packing medi
Page 176 and 177: the condensate rate, productivity f
Page 178 and 179: esult, rather than PCM media which
Page 180 and 181: Figure 7.18: Effect of PCM thermal
Page 182 and 183: 8 Optimization of HDH plant In this
Page 184 and 185: The MATLAB model describes how the
Page 186 and 187: less steep than that of the distill
Page 188 and 189: 8.3.4 Effect of hot water flow rate
Page 190 and 191: storage materials and thus it can h
Page 192 and 193: for latent heat storage would be ob
Page 194 and 195: When T m becomes sufficiently highe
Page 196 and 197: 9 Summary and conclusions 9.1 Summa
Page 198 and 199: productivities at any cooling water
Page 200 and 201: [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
Page 206 and 207: [109] Mehling H., Hiebler S. and Zi
Page 208 and 209: [139] Belessiotis V, Delyannis E (2
Page 210 and 211: Appendices Appendix A A1. PCM Therm
Page 212 and 213: A3. Constants and Thermo-physical p
Page 214 and 215: From the above correlation, the con
Page 216 and 217: The Ergun analogy factor J h repres
Page 218 and 219: 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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