260 B. Zalba et al. / Applied Thermal Engineering 23 (2003) 251–283Table 4Organic substances <strong>with</strong> potential use as PCMCompoundMelting temperature(°C)Heat of fusi<strong>on</strong>(kJ/kg)Thermal c<strong>on</strong>ductivity(W/m K)Density(kg/m 3 )Paraffin C 14 4.5 [1] 165 [1] n.a. n.a.Paraffin C 15 –C 16 8 [1] 153 [1] n.a. n.a.Polyglycol E400 8 [4,11] 99.6 [4,11] 0.187 (liquid, 38.6 °C) [4,11] 1125 (liquid, 25 °C) [4,11]0.185 (liquid, 69.9 °C) [11] 1228 (solid, 3 °C) [4,11]Dimethyl-sulfoxide 16.5 [28] 85.7 [28] n.a. 1009 (solid and liquid) [28](DMS)Paraffin C 16 –C 18 20–22 [29] 152 [29] n.a. n.a.Polyglycol E600 22 [4,11] 127.2 [4,11] 0.189 (liquid, 38.6 °C) [4,11] 1126 (liquid, 25 °C) [4,11]0.187 (liquid, 67.0 °C) [11] 1232 (solid, 4 °C) [4,11]Paraffin C 13 –C 24 22–24 [1] 189 [1] 0.21 (solid) [1] 0.760 (liquid, 70 °C) [1]0.900 (solid, 20 °C) [1]1-Dodecanol 26 [9] 200 [9] n.a. n.a.Paraffin C 18 28 [1] 244 [1] 0.148 (liquid, 40 °C) [30] 0.774 (liquid, 70 °C) [1]27.5 [30] 243.5 [30] 0.15 (solid) [1] 0.814 (solid, 20 °C) [1]0.358 (solid, 25 °C) [30]1-Tetradecanol 38 [9] 205 [9]Paraffin C 16 –C 28 42–44 [1] 189 [1] 0.21 (solid) [1] 0.765 (liquid, 70 °C) [1]0.910 (solid, 20 °C) [1]Paraffin C 20 –C 33 48–50 [1] 189 [1] 0.21 (solid) [1] 0.769 (liquid, 70 °C) [1]0.912 (solid, 20 °C) [1]Paraffin C 22 –C 45 58–60 [1] 189 [1] 0.21 (solid) [1] 0.795 (liquid, 70 °C) [1]0.920 (solid, 20 °C) [1]Parffin wax 64 [4,11] 173.6 [4,11] 0.167 (liquid, 63.5 °C) [4,11] 790 (liquid, 65 °C) [4,11]266 [6] 0.346 (solid, 33.6 °C) [4,11] 916 (solid, 24 °C) [4,11]0.339 (solid, 45.7 °C) [11]Polyglycol E6000 66 [4,11] 190.0 [4,11] n.a. 1085 (liquid, 70 °C) [4,11]1212 (solid, 25 °C) [4,11]Paraffin C 21 –C 50 66–68 [1] 189 [1] 0.21 (solid) [1] 0.830 (liquid, 70 °C) [1]0.930 (solid, 20 °C) [1]Biphenyl 71 [4,11] 119.2 [4,11] n.a. 991 (liquid, 73 °C) [4,11]1166 (solid, 24 °C) [11]Propi<strong>on</strong>amide 79 [11] 168.2 [11] n.a. n.a.Naphthalene 80 [4,11] 147.7 [4,11] 0.132 (liquid, 83.8 °C) [4,11] 976 (liquid, 84 °C) [4,11]0.341 (solid, 49.9 °C) [4,11] 1145 (solid, 20 °C) [4,11]0.310 (solid, 66.6 °C) [11]Erythritol 118.0 [31] 339.8 [31] 0.326 (liquid, 140 °C) [31] 1300 (liquid, 140 °C) [31]0.733 (solid, 20 °C) [31] 1480 (solid, 20 °C) [31]HDPE 100–150 [32] 200 [32] n.a. n.a.Trans-1,4-polybutadiene145 [33] 144 [33] n.a. n.a.(TPB)n.a.: not available.2.3.2. Corrosi<strong>on</strong> of the <strong>materials</strong>Most references <strong>on</strong> corrosi<strong>on</strong> tests using salt hydrates were performed <strong>with</strong> diluted salt hydrates,as typically used in the chemical industry, and <strong>on</strong>ly a few presented results, usually based
Table 5Organic eutectics <strong>with</strong> potential use as PCMCompoundMelting temperature(°C)B. Zalba et al. / Applied Thermal Engineering 23 (2003) 251–283 261Heat of fusi<strong>on</strong>(kJ/kg)Thermal c<strong>on</strong>ductivity(W/m K)37.5% Urea þ 63:5% acetamide 53 [1] n.a. n.a. n.a.67.1% Naphthalene þ67 [11] 123.4 [11] 0.136 (liquid, 78.5 °C) [11] n.a.32:9% benzoic acid0.130 (liquid, 100 °C) [11]0.282 (solid, 38 °C) [11]0.257 (solid, 52 °C) [11]% in weight; n.a.: not available.Density(kg/m 3 )<strong>on</strong> observati<strong>on</strong> over experimental set-ups [78,79]. Porisini [80] tested the corrosi<strong>on</strong> of four commerciallyavailable salt hydrates used as PCMs in 1988. Recently, Cabeza et al. [81–84] studiedcorrosi<strong>on</strong> resistance of five comm<strong>on</strong> metals (aluminium, brass, copper, steel and stainless steel) inc<strong>on</strong>tact <strong>with</strong> molten salt hydrates (zinc nitrate hexahydrate, sodium hydrogen phosphate dodecahydrate,calcium chloride hexahydrate, sodium carb<strong>on</strong>ate, potassium hydrogen carb<strong>on</strong>ate,potassium chloride, water, sodium acetate trihydrate, and sodium thiosulphate pentahydrate) inan immersi<strong>on</strong> corrosi<strong>on</strong> test.Some investigati<strong>on</strong>s have been c<strong>on</strong>cerned <strong>with</strong> corrosi<strong>on</strong> of molten salts at high temperature.Already in 1980, Heine et al. [21] studied the corrosi<strong>on</strong> performance of six molten salts meltingbetween 235 and 857 °C vs. four metals used at these temperatures.2.3.3. Encapsulati<strong>on</strong> of the <strong>materials</strong>The encapsulati<strong>on</strong> of the PCM has developed interest in several researchers. Advantages anddisadvantages of different geometries of PCM encapsulati<strong>on</strong> <strong>with</strong> different <strong>materials</strong> and theircompatibility was discussed by Lane [3]. The freezing and melting processes of water c<strong>on</strong>tained inspherical elements was studied experimentally by Eames et al. [85], proposing semi empiricalequati<strong>on</strong>s that allow the mass of ice <strong>with</strong>in a sphere to be predicted at any time during the freezingor melting processes. Earlier, Bedecarrats et al. [86,87] and All<strong>on</strong>cle [88], studied the crystallizati<strong>on</strong>process of an organic eutectic in a spherical encapsulati<strong>on</strong>.For the use of PCM in buildings applicati<strong>on</strong>s, an encapsulati<strong>on</strong> of PCM (50–80%) <strong>with</strong>unsaturated polyester matrix (45–10%), and water (5–10%) was studied by Morikama et al.[89]. Polymerisati<strong>on</strong> of PCMs has been also studied for other applicati<strong>on</strong>s, like insulati<strong>on</strong><strong>materials</strong> for use in clothing or bedding articles [90]. In the same area, Inaba [91] and Lee andChoi [92] propose using the <strong>storage</strong> substance integrated <strong>with</strong> the building <strong>materials</strong> <strong>with</strong>outencapsulati<strong>on</strong> (‘‘Shape-stabilised paraffin’’: 74% paraffin þ 26% high-density polyethylene(HDPE)). Structural stability is achieved using HDPE which retains the paraffin when in liquid<strong>phase</strong>.Revankar et al. studied the presence of c<strong>on</strong>centrated voids in encapsulated PCM use for spacebasedheat ex<strong>change</strong>rs [93].For many applicati<strong>on</strong>s, PCMs are microencapsulated, and this has been studied by severalresearchers [94] and developed by companies like BASF[95]. Nevertheless, the potential use ofmicroencapsulated PCMs in various <strong>thermal</strong> c<strong>on</strong>trol applicati<strong>on</strong>s is limited to some extent by