# The Impact of Heat Exchangers’ Constructions on the Melting and Solidification Time of Phase Change Materials

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## Abstract

**:**

## 1. Introduction

## 2. Basics of Heat Transfer in LHTES

#### 2.1. The Influence of HTF Inlet Parameters

#### 2.2. The Application of Multiple PCMs

## 3. Types of Heat Exchangers Used in LHTES Systems

#### 3.1. Plate Heat Exchangers

#### 3.2. Helical-Coil Heat Exchangers

#### 3.3. Double-Tube Heat Exchangers

#### 3.4. Triple-Tube Heat Exchangers

#### 3.5. Multi-Tube Heat Exchangers

#### 3.6. Heat Exchangers with Encapsulated PCMs

^{2}, respectively. Therefore, the melting time was reduced by 35.6%. However, Wu et al. [127] also reduced the capsules’ diameter from 100 to 60 mm and the reduction of melting and solidification time was only 6.4% and 8%, respectively. A possible explanation of the differences in results achieved by those two research groups, i.e., Karthikeyan et al. [128] and Wu et al. [127], could be as follows. The decrease in capsules’ diameter results not only in an enlarged heat transfer surface area but also in a decreased porosity of a packed bed. The porosity of the packed bed can be defined as the ratio of the volume of voids to the total volume of a packed bed [126,129]. Thus, as the porosity decreases, a larger amount of PCM is in the heat exchanger, which might extend the phase change time, which was reported by Wu et al. [36], who investigated the influence of packed bed porosity on the PCM’s solidification time. It was concluded that as the porosity decreased from 0.55 to 0.35, the solidification time increased, but the authors did not report the exact value of the solidification time extension. A similar finding was reported by Raul et al. [130], who investigated the phase change time of PCM packed beds with porosities 0.6, 0.7, 0.8, and 0.9. It was found that when the porosity decreased from 0.9 to 0.6, the melting and solidification time increased by 73% and 9%, respectively. Additionally, the capsules’ diameter also affects the mechanism of heat transfer inside the capsules, which was reported by Bellan et al. [22]. They concluded that the natural convection in small capsules was insignificant; thus, the difference between the melting and solidification time was slight. But, as the diameter increased, the convective heat transfer was augmented and an increasing difference between the melting and solidification time was observed.

#### 3.7. Enclosure-Type Heat Exchangers

#### 3.8. Other Types of Heat Exchangers

## 4. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Nomenclature

DTHX | double-tube heat exchanger |

HCHX | helical-coil heat exchanger |

HTF | heat transfer fluid |

HX | heat exchanger |

LHTES | latent heat thermal energy storage |

MTHX | multi-tube heat exchanger |

PCM | phase change material |

TES | thermal energy storage |

TTHX | triple-tube heat exchanger |

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**Figure 1.**Heat exchanger with multiples phase change materials (PCMs) [46]: (

**a**) Horizontal descending arrangement; (

**b**) horizontal descending arrangement; (

**c**) vertical descending arrangement; (

**d**) vertical ascending arrangement. T

_{m}—melting temperature.

**Figure 3.**Plate heat exchanger with upward heat transfer fluid (HTF) flow. D

_{c}—coil diameter, D

_{t}—tube diameter.

**Figure 4.**The new type of helical-coil heat exchanger (HX): (

**a**) Side view, (

**b**) front view [72]. s—spacing between flat spiral tubes.

**Figure 5.**Vertical double-tube HX: (

**a**) Cylinder model with downward HTF flow direction, (

**b**) pipe model with upward HTF flow direction.

**Figure 6.**Cross-section of: (

**a**) Concentric; (

**b**) non-concentric Double-Tube Heat Exchanger (DTHX) [16].

**Figure 7.**Cross-sections of the cylinder model DTHX: (

**a**) Circular inner tube, (

**b**) horizontal ellipse inner tube, (

**c**) vertical ellipse inner tube [77].

**Figure 8.**The double-tube helical-coil HX [81].

**Figure 11.**Triple- or triplex-tube heat exchangers (TTHXs) with: (

**a**) Horizontal ellipse inner tube; (

**b**) vertical ellipse inner tube; (

**c**) circular inner tube [77].

**Figure 12.**Cross-section of a TTHX with a possible arrangement of longitudinal fins [112].

**Figure 13.**Cross-section of the TTHX: (

**a**) Two horizontal inner tubes; (

**b**) two vertical inner tubes; (

**c**) four inner tubes; (

**d**) four inner tubes with the modified arrangement; (

**e**) horizontal elliptical outer tube and two inner tubes; (

**f**) vertical elliptical outer tube and two inner tubes; (

**g**) horizontal elliptical outer tube and four inner tubes; (

**h**) vertical elliptical outer tube and four inner tubes [21].

**Figure 14.**The length and arrangement of fins: (

**a**) Equal-length fins; (

**b**) fins moved down, the length of fin 2 and 3 reduced by 50% and 75%, respectively, compared to fin 1 [26].

**Figure 18.**Cross-section of the heat exchanger with heat–pipe–shell and inclination angle of the HTF U-pipes: (

**a**) 0, (

**b**) 90° [151].

Reference | Number of PCMs | Type of PCM | Melting Temperature of PCM, (°C) | Ratio of PCMs | Type of Research | Investigated Process |
---|---|---|---|---|---|---|

Elfeky et al. [24] | 3 | MgCl_{2}–KCl–NaCl | 505 | 1:1:1 (volume) | Numerical | Melting Solidification |

MgCl_{2}–NaCl | 440 | |||||

Li_{2}CO_{3}–K_{2}CO_{3} | 382 | |||||

Sunku Prasad et al. [31] | 3 | KOH | 360 | 1:1:1 (volume) | Numerical | Melting Solidification |

KNO_{3} | 335 | |||||

NaNO_{3} | 306 | |||||

Wang et al. [41] | 3 | Not available | Not available | 1:1:1 16:6:8 (mass) | Numerical | Melting |

Aldoss and Rahman [43] | 2, 3 | Not available | 42–44 | 1:1 1:1:1 (volume) | Numerical | Melting Solidification |

50–52 | ||||||

60–62 | ||||||

Mohammadnejad and Hossainpour [44] | 3 | KOH | 378–380 | Not available | Numerical | Solidification |

KNO_{3} | 333–336 | |||||

NaNO_{2} | 277–304 | |||||

Wang et al. [45] | 3 | NaCl-MgCl_{2} | Not available | 1:1:1 (mass) | Numerical | Solidification |

Kurnia et al. [46] | 3 | Not available | 46–48 | Not available | Numerical | Melting Solidification |

26–28 | ||||||

36–38 | ||||||

Gong and Mujumdar [48] | 2, 3, 5 | Not available | Not available | Not available | Numerical | Melting Solidification |

Xu et al. [49] | 3 | Li_{2}CO_{3}–K_{2}CO_{3} | 488 | Not available | Numerical | Melting Solidification |

NaNO_{3} | 307 | |||||

NaNO_{3}–KNO_{3} | 220 | |||||

Tao et al. [50] | 2 | LiF–CaF_{2} | 767 | 1:1 (volume) | Numerical | Melting |

LiF–MgF_{2} | 746 | |||||

Ezra et al. [55] | 2–180 | Not available | Not available | 1:1 (mass) | Numerical | Melting |

Cheng and Zhai [56] | 3 | PCM1 ^{1} | 13 | 1:1:1 (volume) | Numerical Experimental | Solidification |

PCM2 ^{1} | 14.5 | |||||

PCM3 ^{1} | 17 | |||||

Li et al. [57] | 3 | K_{2}CO_{3}–Na_{2}CO_{3} | 710 | 5:4:3 3:4:5 2.5:4:5.5 (volume) | Numerical | Melting |

Li_{2}CO_{3}–Na_{2}CO_{3}–K_{2}CO_{3} | 550 | |||||

Li_{2}CO_{3}–K_{2}CO_{3}–Na_{2}CO_{3} | 397 | |||||

Li et al. [58] | 3 | HS-W1 | 5.3 | ^{2} | Numerical Experimental | Solidification |

HS-W2 | 6.5 | |||||

Paraffin C_{15} | 10.0 | |||||

Ahmed et al. [59] | 3 | Galactitol | 187 | 1:8:1 2.5:5:2.5 4:2:4 (volume) | Numerical | Melting Solidification |

D-mannitol | 165 | |||||

Mixture of galactitol and d-mannitol | 153 | |||||

Zhao et al. [60] | 3 | NaNO_{3} | 100 | 1:1:1 (mass) | Experimental | Melting |

NaNO_{3}–Ca(NO_{3})_{2} | 200 | |||||

NaNO_{3}–KNO_{3}–LiNO_{3} | 300 | |||||

Yuan et al. [61] | 3 | Li2CO3–K2CO3 3 | 500 | 1:1:1 (volume) | Experimental | Melting Solidification |

Li2CO3–K2CO3 4 | 484 | |||||

Li2CO3–K2CO3–Na2CO3 | 422 | |||||

Peiró et al. [62] | 2 | Hydroquinone | 165–172 | Not available | Experimental | Melting |

D-mannitol | 155–162 |

^{1}Mixtures of capric–lauric–oleic acid. Mole fractions of oleic acid: 10%, 6%, and 2% for PCM1, PCM2, and PCM3, respectively.

^{2}Investigated volume ratios: 1:2:3, 1:3:2, 2:1:3, 1:1:1, 2:3:1, 3:1:2, 3:2:1, 0:1:0.

^{3}Weight fractions of Li

_{2}CO

_{3}and K

_{2}CO

_{3}: 34.83% and 65.17%.

^{4}Weight fractions of Li

_{2}CO

_{3}and K

_{2}CO

_{3}: 46.59% and 53.41%.

Reference | PCM | HTF | Type of Research | Investigated Process | HX Orientation | Flow Direction | Parameters Influencing or Heat Transfer Enhancement Technique |
---|---|---|---|---|---|---|---|

Johnson et al. [12] | KNO_{3}–NaNO_{3} | Mobiltherm 603 | Numerical Experimental | Solidification | Vertical | Not available | HTF inlet temperature |

HTF flow rate | |||||||

The addition of heat transfer structures | |||||||

Medrano et al. [23] | Rubitherm RT35 | Water | Experimental | Melting Solidification | Not available | Not available | Types of HXs |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Saeed et al. [40] | Hexadecane | Water | Experimental | Melting Solidification | Not available | Not available | Number of plates |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Gürel [63] | RT35 N-octadecane | Water | Numerical | Melting | Horizontal | Downward | Number of plates |

HTF inlet temperature | |||||||

PCM layer thickness | |||||||

Hoseinzadeh et al. [64] | CaCl_{2}∙6H_{2}O RT25 | Air | Numerical | Melting | Horizontal | - | Multiple PCMs |

Geometrical parameters of HX | |||||||

HTF inlet temperature | |||||||

HTF inlet velocity | |||||||

Liu et al. [65] | Not available | Glycol | Numerical | Melting | Not available | Not available | HTF inlet temperature |

HTF flow rate | |||||||

Dimensions of the HX | |||||||

Vogel et al. [66] | KNO_{3}–NaNO_{3} | Thermal oil | Numerical Experimental | Melting | Vertical | Downward (melting) Upward (solidification) | Dimensions of the HX |

Jmal and Baccar [67] | Paraffin C_{18} RT27 | Air | Numerical | Solidification | Horizontal | - | Number of fins |

Elbahjaoui and El Qarnia [68] | RT42 RT50 RT60 | Water | Numerical | Melting Solidification | Vertical | Downward | Number of PCM slabs |

HTF flow rate |

Reference | PCM | HTF | Type of Research | Investigated Process | HX Orientation | Flow Direction | Parameters Influencing or Heat Transfer Enhancement Technique |
---|---|---|---|---|---|---|---|

Kabbara et al. [13] | Dodecanoic acid | Water (solidification) Water–glycol (melting) | Experimental | Melting Solidification | Vertical | Downward (solidification) Upward (melting) | HTF inlet temperature |

HTF flow rate | |||||||

Anish et al. [14] | Erythritol Xylitol | Therminol-55 | Experimental | Melting Solidification | Vertical | Downward Upward | Type of a PCM |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Saydam et al. [18] | Paraffin wax | Ethylene glycol–water mixture | Experimental | Melting Solidification | Vertical | Upward Downward | HTF inlet temperature |

HTF flow rate | |||||||

HTF flow direction | |||||||

Korti and Tlemsani [19] | Refined paraffin wax Semi-refined paraffin wax Classical paraffin wax | Water | Experimental | Melting Solidification | Vertical | Downward | HTF inlet temperature |

HTF flow rate | |||||||

Type of a PCM | |||||||

Anish et al. [20] | Erythritol | Therminol-55 | Experimental | Melting Solidification | Vertical | Downward Upward | HTF inlet temperature |

HTF flow rate | |||||||

Rahimi et al. [69] | RT-35 | Water | Experimental | Melting | Horizontal | - | HTF inlet temperature |

Helical-coil diameter | |||||||

Mahdi et al. [73] | Paraffin wax | Water | Experimental | Melting | Vertical | Upward | Coil geometry |

HTF inlet temperature | |||||||

Mahdi et al. [38] | Paraffin wax | Water | Experimental | Melting Solidification | Vertical | Upward | HTF inlet temperature |

HTF flow rate | |||||||

Salyan et al. [28] | D-mannitol D-mannitol with gallium | Therminol 55 | Experimental | Melting Solidification | Vertical | Not available | Addition of metal inserts |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Yang et al. [32] | RT54HC/expanded graphite | Water | Numerical Experimental | Melting | Vertical | Not available | HTF inlet temperature |

HTF flow rate | |||||||

Chen et al. [37] | Paraffin with expanded graphite | Water | Numerical Experimental | Melting | Horizontal | - | HTF inlet temperature |

HTF flow rate | |||||||

Helical-coil diameter | |||||||

Du et al. [39] | Paraffin Paraffin with copper nanoparticles | Water | Numerical Experimental | Melting | Vertical | Downward | Nano-enhanced PCM |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Rahimi et al. [70] | RT35 | Water | Experimental | Melting | Horizontal | - | Helical-coil diameter |

HTF inlet temperature | |||||||

Ahmadi et al. [71] | RT50 | Water | Numerical | Melting | Horizontal | - | Helical-coil diameter |

Tube diameter | |||||||

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Ardahaie et al. [72] | RT35 | Water | Numerical | Melting | Horizontal 45° Vertical | Upward | Helical-coil geometry |

Inclination angle | |||||||

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Zhang et al. [74] | RT54 with 3 wt.% of carbon fiber | Water | Experimental | Melting Solidification | Vertical | Not available | HTF inlet temperature |

HTF flow rate | |||||||

Tayssir et al. [75] | Paraffin wax | Water | Experimental | Melting | Vertical | Not available | HTF inlet temperature |

HTF flow rate | |||||||

Ling et al. [76] | Mannitol | Thermal oil (melting), Water (solidification) | Experimental | Melting Solidification | Vertical | Not available | HTF inlet temperature |

HTF flow rate |

Reference | PCM | HTF | Type of Research | Investigated Process | HX Orientation | HTF Location, (Flow Direction) | Parameters Influencing or Heat Transfer Enhancement Technique |
---|---|---|---|---|---|---|---|

Kousha et al. [15] | RT35 | Water | Numerical Experimental | Melting Solidification | 0–90° | Inner tube, (not available) | Inclination angle |

HTF inlet temperature | |||||||

Kadivar et al. [16] | N-eicosane RT31 RT35 RT44HC | ^{1} | Numerical | Melting Solidification | Horizontal | Inner tube, (-) | Inner tube eccentricity |

PCM type | |||||||

The ratio of the shell to tube diameter | |||||||

Mehta et al. [82] | Stearic acid | Water | Numerical Experimental | Melting Solidification | Horizontal Vertical | Inner tube, (upward) | Inclination angle |

HTF inlet temperature | |||||||

Karami and Kamkari [29] | Lauric acid | Water | Experimental | Melting | Vertical | Inner tube, (upward) | Fins |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Mahdi et al. [89] | Paraffin wax | Water | Numerical Experimental | Melting | Horizontal Vertical | Inner tube, (not available) | Fins |

Inclination angle | |||||||

HTF flow rate | |||||||

HTF inlet temperature | |||||||

Al Siyabi et al. [80] | RT35 | Water | Numerical Experimental | Melting | Horizontal Vertical 45° | Inner tube, (not available) | Inclination angle |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Chen et al. [77] | RT50 | Water | Numerical Experimental | Melting Solidification | Horizontal | Inner tube Annulus, (-) | PCM location |

HX shape | |||||||

Han et al. [78] | Solar salt | Air | Numerical | Melting | Horizontal Vertical | Inner tube Annulus, (downward and upward) | PCM location |

Inclination angle | |||||||

HTF flow direction | |||||||

Mahdi et al. [79] | RT50 | ^{1} | Numerical | Melting Solidification | Horizontal | Inner tube Annulus, (-) | PCM location |

HTF inlet temperature | |||||||

Mahdi et al. [81] | RT50 | Water | Numerical | Melting | Vertical | Not available | Shape of HX |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Mehta et al. [83] | Stearic acid | Water | Experimental | Melting | 0–90° | Inner tube, (upward) | Inclination angle |

Li et al. [84] | RT27 | Water | Numerical | Melting | Horizontal | Inner tube, (-) | Inner tube eccentricity |

Inner tube diameter | |||||||

HTF inlet temperature | |||||||

Seddegh et al. [85] | RT60 | Water | Numerical Experimental | Melting Solidification | Vertical | Inner tube, (not available) | Geometric design |

Sodhi et al. [86] | NaNO_{3} | Air | Numerical | Melting Solidification | Horizontal | Inner tube, (-) | Shape of HX |

HTF inlet temperature | |||||||

HTF velocity | |||||||

Fins | |||||||

Agyenim et al. [87] | Erythritol | Silicon oil | Experimental | Melting Solidification | Horizontal | Inner tube, (-) | Fins |

Scharinger-Urschitz et al. [88] | Sodium nitrate | Thermal oil | Experimental | Melting Solidification | Vertical | Inner tube, (upward) | Fins |

Deng et al. [91] | Lauric acid | ^{1} | Numerical | Melting | Horizontal | Inner tube, (-) | Fin arrangement |

Fin number | |||||||

Fin length | |||||||

HTF inlet temperature | |||||||

Nie et al. [92] | Lauric acid | ^{1} | Numerical | Melting Solidification | Horizontal | Inner tube, (-) | Fin arrangement |

Fin number | |||||||

Fin length | |||||||

Deng et al. [90] | Lauric acid | ^{1} | Numerical | Melting | Horizontal | Inner tube, (-) | Fin arrangement |

Fin length | |||||||

HTF inlet temperature | |||||||

Caron-Soupart et al. [93] | RT35-HC | Water | Experimental | Melting Solidification | Vertical | Inner tube, (downward-melting; upward-solidification) | Fins |

Pu et al. [94] | RT35 | Water | Numerical | Melting | Vertical | Inner tube, (downward) | Fin number |

Fin length | |||||||

Fin arrangement | |||||||

Aly et al. [95] | Formic acid | ^{1} | Numerical | Solidification | Horizontal | Inner tube, (-) | Fin shape |

Zhang et al. [96] | Lauric acid | ^{1} | Numerical | Melting Solidification | Horizontal | Inner tube, (-) | Fin shape |

Luo and Liao [97] | Lauric acid | ^{1} | Numerical | Melting | Vertical | Inner tube, (-) | Fin shape |

Sheikholeslami et al. [98] | Water Water with copper nanoparticles | ^{1} | Numerical | Solidification | Not available | Inner tube, (-) | Fin shape |

Mahdavi et al. [100] | RT55 | Not available | Numerical | Melting Solidification | Vertical | Inner tube, (upward) | Number of heat pipes |

Pizzolato et al. [101] | Not available | ^{1} | Numerical | Melting Solidification | Horizontal | Inner tube, (-) | Fin shape |

Kalapa and Devanuri [102] | Lauric acid | Not available | Numerical | Melting | Vertical | Inner tube, (downward) | HTF inlet parameters |

HX dimensions |

^{1}The HTF was substituted by the constant temperature of the heat transfer surface.

Reference | PCM | HTF | Type of Research | Investigated Process | HX Orientation | HTF Location, (Flow Direction) | Parameters Influencing or Heat Transfer Enhancement Technique |
---|---|---|---|---|---|---|---|

Al-Abidi et al. [104] | RT82 | Water | Experimental | Melting Solidification | Horizontal | Inner and outer tube, (-) | HTF inlet temperature |

HTF flow rate | |||||||

Chen et al. [77] | RT50 | Water | Numerical Experimental | Melting Solidification | Horizontal | Middle tube, (-) | HX shape |

Yang et al. [103] | Ba(OH)_{2}∙8H_{2}O | Water | Numerical | Melting | Not available | Inner and outer tube, (not available) | HTF inlet temperature |

HTF flow rate | |||||||

Gorzin et al. [105] | RT50 | Not available | Numerical | Solidification | Not available | Middle tube, (-) | HX shape |

HTF inlet temperature | |||||||

Shahsavar et al. [106] | RT35 | Water | Numerical | Melting Solidification | Vertical | Inner tube (upward), outer tube (downward) | HX shape |

Abdulateef et al. [109] | RT82 | Water | Numerical Experimental | Melting Solidification | Not available | Inner and outer tube, (-) | Number of fins |

Fin length | |||||||

Fin thickness | |||||||

Abdulateef et al. [110] | RT82 | Not available | Numerical Experimental | Solidification | Horizontal | Inner and outer tube, (-) | Fin shape |

HTF flow rate | |||||||

Alizadeh et al. [111] | Water | Not available | Numerical | Solidification | Not available | Inner and outer tube, (not available) | Fin length |

Fin thickness | |||||||

Shape of fins | |||||||

Al-Abidi et al. [113] | RT82 | Water | Numerical | Melting | Horizontal | Inner and outer tube, (-) | Number of fins |

Fin length | |||||||

Fin thickness | |||||||

Mat et al. [112] | RT82 | Water | Numerical | Melting | Horizontal | Inner tube Outer tube Inner and outer tube, (-) | Fin arrangement |

Fin length | |||||||

HTF inlet temperature | |||||||

Mahdi and Nsofor [107] | RT82 | Water | Numerical | Melting | Horizontal | Inner and outer tube, (-) | Fin length |

Fin thickness | |||||||

HTF inlet temperature | |||||||

Mahdi and Nsofor [108] | RT82 | Water | Numerical | Solidification | Horizontal | Inner and outer tube, (-) | Fin length |

Fin thickness | |||||||

Mahdi et al. [114] | RT82 | Not available | Numerical | Melting | Horizontal | Inner and outer tube, (-) | Number of fins |

Fin length | |||||||

Fin arrangement | |||||||

Zarei et al. [115] | RT82 | Water | Numerical | Solidification | Horizontal | Inner and outer tube, (-) | Fin arrangement |

Eslamnezhad et al. [116] | RT82 | Water | Numerical | Melting | Horizontal | Inner and outer tube, (-) | Fin arrangement |

Eccentricity of the inner tube | |||||||

Mahdi and Nsofor [117] | RT82 | Water | Numerical | Melting | Horizontal | Inner and outer tube, (-) | Copper foam porosity |

HTF inlet temperature | |||||||

Mahdi and Nosfor [118] | RT82 | Water | Numerical | Solidification | Horizontal | Inner and outer tube, (-) | Copper foam porosity |

Reference | PCM | HTF | Type of Research | Investigated Process | HX Orientation | HTF Location, (Flow Direction) | Parameters Influencing or Heat Transfer Enhancement Technique |
---|---|---|---|---|---|---|---|

Esapour et al. [17] | RT35 | Water | Numerical | Melting Solidification | Horizontal | Inner tubes and space between outer and middle tubes, (-) | Number of tubes |

Arrangement of tubes | |||||||

Copper foam | |||||||

Copper foam porosity | |||||||

Pourakabar and Rabienataj Darzi [21] | N-eicosane | Not available | Numerical | Melting Solidification | Horizontal | Inner tubes, (-) | The shape of the shell |

Number of tubes | |||||||

Arrangement of tubes | |||||||

Copper foam | |||||||

Anish et al. [33] | Erythritol | Therminol-55 | Experimental | Melting Solidification | Horizontal | Inner tubes, (-) | HTF inlet temperature |

HTF flow rate | |||||||

Esapour et al. [124] | RT35 | Water | Numerical | Melting | Not available | Inner tubes and space between outer and middle tubes, (-) | Number of tubes |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Esapour et al. [121] | RT35 | Water | Numerical | Melting | Horizontal | Inner tubes and space between outer and middle tubes, (-) | Number of tubes |

Arrangement of tubes | |||||||

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Kousha et al. [119] | RT35 | Water | Experimental | Melting Solidification | Horizontal | Inner tubes, (-) | Number of tubes |

HTF inlet temperature | |||||||

Sodhi et al. [120] | Sodium nitrate | Not available | Numerical | Melting Solidification | Not available | Inner tubes, (not available) | Number of tubes |

Kuboth et al. [122] | RT42 | Water | Numerical | Solidification | Vertical | Inner tubes, (downward) | Fin arrangement |

Bhagat et al. [123] | A164 | Hytherm 600 | Numerical Experimental | Melting Solidification | Vertical | Inner tubes, (downward) | Number of fins |

Fin thickness | |||||||

Fin height | |||||||

Raul et al. [125] | A164 | Hytherm 600 | Experimental | Solidification | Vertical | Inner tubes, (downward) | HTF inlet temperature |

HTF flow rate |

Reference | PCM | HTF | Type of Research | Investigated Process | Capsule Diameter, (mm) | HTF Flow Direction | Parameters Influencing or Heat Transfer Enhancement Technique |
---|---|---|---|---|---|---|---|

Bellan et al. [22] | Sodium nitrate | Therminol 66 | Numerical | Melting Solidification | 10 15 20 25 | Upward | Capsule diameter |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Tank length and diameter | |||||||

Karthikeyan et al. [128] | Paraffin wax | Air | Numerical | Melting | 60–100 | Upward | Capsule diameter |

HTF inlet temperature | |||||||

HTF flow rate | |||||||

Wu and Fang [35] | Myristic acid | Water | Numerical | Solidification | 50 | Upward | HTF inlet temperature |

HTF flow rate | |||||||

Wu et al. [36] | Paraffin wax | Water | Numerical | Solidification | 50 | Upward | HTF inlet temperature |

HTF flow rate | |||||||

Packed bed porosity | |||||||

Wu et al. [127] | N-tetradecane | The aqueous ethylene glycol solution | Numerical | Melting Solidification | 60–150 | Downward | HTF inlet temperature |

HTF flow rate | |||||||

Packed bed porosity | |||||||

Capsule diameter | |||||||

Li et al. [129] | A mixture of Li_{2}CO_{3}–K_{2}CO_{3}–Na_{2}CO_{3} | Air | Numerical Experimental | Melting Solidification | 15–40 | Downward (melting) Upward (solidification) | HTF inlet temperature |

HTF flow rate | |||||||

Capsule diameter | |||||||

Raul et al. [130] | A164 | Hytherm 600 | Numerical Experimental | Melting Solidification | 21 31 41 51 | Downward | HTF inlet temperature |

HTF flow rate | |||||||

Capsule diameter | |||||||

Packed bed porosity | |||||||

Mawire et al. [131] | Sn–Pb | Sunflower oil | Experimental | Melting Solidification | 50 | Downward | HTF inlet temperature |

HTF flow rate |

Reference | PCM | Type of Research | Investigated Process | Parameters Influencing or Heat Transfer Enhancement Technique |
---|---|---|---|---|

Joshi and Rathod [26] | Lauric acid | Numerical | Melting | Fin length |

Fin arrangement | ||||

Tiari et al. [27] | RT55 | Experimental | Melting Solidification | Heat pipe |

HTF flow rate | ||||

HTF inlet temperature | ||||

Motahar and Khodabandeh [141] | N-octadecane | Experimental | Melting Solidification | Heat pipe |

Heat source temperature | ||||

Yang et al. [30] | NaNO_{3} | Numerical | Melting | HTF flow conditions (laminar/turbulent) |

Heat pipe | ||||

HTF type | ||||

Ren et al. [134] | N-eicosane | Numerical | Melting | Fin shape |

Fin length | ||||

Fin thickness | ||||

Heat source temperature | ||||

Inclination angle | ||||

Duan et al. [144] | N-octadecane | Numerical | Melting | Heat source location |

Kamkari and Amlashi [135] | Lauric acid | Numerical Experimental | Melting | Inclination angle |

Heat source temperature | ||||

Kamkari and Groulx [136] | Lauric acid | Experimental | Melting | Number of fins |

Inclination angle | ||||

Karami and Kamkari [137] | Lauric acid | Numerical | Melting | Inclination angle |

Number of fins | ||||

Abdi et al. [138] | Lauric acid | Numerical | Melting | Heat source temperature |

Number of fins | ||||

Fin length | ||||

Ji et al. [139] | RT42 | Numerical | Melting | Fins inclination angle |

Fin length | ||||

Ladekar et al. [140] | Paraffin wax | Experimental | Melting Solidification | Heat pipe |

Copper rods | ||||

HTF flow rate | ||||

Wu et al. [142] | Paraffin with expanded graphite | Experimental | Melting | Heat pipe |

Jiang and Qu [143] | Not available | Numerical Experimental | Melting Solidification | Heat pipe |

Robak et al. [145] | N-octadecane | Experimental | Melting Solidification | Fins |

Heat pipe | ||||

Sharifi et al. [146] | NaNO_{3} | Numerical | Melting | Heat pipe |

Sharifi et al. [147] | N-octadecane | Numerical Experimental | Melting Solidification | Copper rods |

Aluminum foil | ||||

Heat pipe |

Reference | PCM | HTF | Type of Research | Investigated Process | HX Orientation | Parameters Influencing or Heat Transfer Enhancement Technique |
---|---|---|---|---|---|---|

Youssef et al. [25] | Paraffin A16 | Glycol–water mixture | Numerical Experimental | Melting Solidification | Vertical | HTF flow rate |

HTF inlet temperature | ||||||

Khan and Khan [34] | RT44HC | Water | Experimental | Melting | Vertical | HTF inlet temperature |

HTF flow rate | ||||||

Lin et al. [148] | Paraffin/expanded graphite | Water | Numerical | Solidification | Vertical | Tubes diameter |

Fins | ||||||

Baffle configuration | ||||||

Lin et al. [149] | Paraffin/expanded graphite | Water | Numerical Experimental | Melting Solidification | Vertical | HTF flow rate |

Khan et al. [150] | Paraffin | Water | Numerical | Melting | Not available | Number of tubes |

Fin length | ||||||

Fin thickness | ||||||

HTF inlet temperature | ||||||

Ebrahimi et al. [151] | RT35 | Water | Numerical | Melting | Horizontal | Heat pipe |

Number of tubes | ||||||

Inclination angle of the HTF tubes | ||||||

Khan and Khan [152] | RT44HC | Water | Experimental | Solidification | Vertical | HTF inlet temperature |

HTF flow rate | ||||||

Khan and Khan [153] | RT44HC | Water | Experimental | Melting Solidification | Vertical | HTF inlet temperature |

HTF flow rate | ||||||

Besagni and Croci [154] | RT26 | Water | Experimental | Melting Solidification | Not available | HTF inlet temperature |

HTF flow rate | ||||||

HTF inlet arrangement | ||||||

Pakalka et al. [155] | RT82 | Water | Experimental | Melting Solidification | Horizontal | Diameter and thickness of tubes |

Number of fins | ||||||

Fins thickness | ||||||

Talukdar et al. [156] | Water | Refrigerant | Numerical Experimental | Melting Solidification | Horizontal | Number of fins |

Amagour et al. [157] | Not available | Water | Experimental | Melting Solidification | Not available | HTF flow rate |

**Table 10.**Types of heat exchangers for PCMs and the main possibilities of phase change time reduction.

Heat Exchanger Type | Schematic Drawing | Improvement | Base Case | Maximum Melting Time Reduction, (%) | Maximum Solidification Time Reduction, (%) |
---|---|---|---|---|---|

Plate-heat exchanger | The addition of zigzag structures into the PCM | HX without additional structures | Not available | 44 | |

Helical-coil heat exchanger | Increasing the coil diameter in the case of horizontally oriented HX | Smaller helical-coil diameter | 73 | Not available | |

Decreasing the distance between the coils in the lower part of the vertically oriented HX | Horizontally oriented HX with coils distributed equally | 30 | Not available | ||

Coil with a large diameter at the bottom and a small diameter at the top of the vertically oriented HX | Traditional coil | 22 | Not available | ||

Double-tube heat exchanger | Moving down the inner tube in the case of pipe model horizontally oriented HX | The tubes arranged concentrically | 86 | 342 (extension) | |

Horizontal cylinder model DTHX | Horizontal pipe model DTHX | 58 | 77 (extension) | ||

Horizontal ellipse inner tube in the cylinder model DTHX | Circular inner tube | 10 | 11 | ||

Double-tube helical-coil HX | Straight DTHX | 60 | Not available | ||

The diameter of the outer tube small at the bottom and large at the top of the vertical HX | Straight outer tube | 12 | Not available | ||

The diameter of the outer tube decreasing along with the HTF flow in the horizontal HX | Straight outer tube | 17 | 28 | ||

Longitudinal fins | Non-finned HX | 59 | 15 | ||

Circular fins | Non-finned HX | 78 | Not available | ||

Fractal Y-shaped or corrugated fins | HX with straight longitudinal fins | 37 | 66 | ||

Triple-tube heat exchanger | Elliptical inner and outer tubes | Circular inner and outer tubes | 41 | 59 | |

Wavy tubes | Straight tubes | 50 | 48 | ||

Moving down the inner tube in the case of pipe model horizontally oriented HX | Concentric tubes | 18 | Not available | ||

Metal foam | HX without metal foam | 89 | 96 | ||

Fins | HX without fins | 65 | 55 | ||

Multi-tube heat exchanger | Increasing the number of tubes | HX with one inner tube | 74 | 50 | |

Changing the arrangement of tubes | - | 72 | 34 | ||

Metal foam | HX without metal foam | 92 | 95 | ||

Elliptical shell | Circular shell | 21 | 38 | ||

Heat exchanger with encapsulated PCMs | Decreasing the diameter of capsules | A larger diameter of the capsules | 36 | 8 | |

Enclosure-type heat exchanger | Vertically oriented HX (heating from bottom) | Horizontally oriented HX (heating from side wall) | 57 | Not available | |

Fins | HX without fins | 68 | Not available | ||

Heat pipe | HX without heat pipe | 94 | Not available | ||

Other types of heat exchangers | Increasing the number of tubes | - | 49 | 50 | |

Heat pipe | HX without heat pipe | 91 | Not available | ||

Fins | HX without fins | Not available | 50 |

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Radomska, E.; Mika, L.; Sztekler, K.; Lis, L. The Impact of Heat Exchangers’ Constructions on the Melting and Solidification Time of Phase Change Materials. *Energies* **2020**, *13*, 4840.
https://doi.org/10.3390/en13184840

**AMA Style**

Radomska E, Mika L, Sztekler K, Lis L. The Impact of Heat Exchangers’ Constructions on the Melting and Solidification Time of Phase Change Materials. *Energies*. 2020; 13(18):4840.
https://doi.org/10.3390/en13184840

**Chicago/Turabian Style**

Radomska, Ewelina, Lukasz Mika, Karol Sztekler, and Lukasz Lis. 2020. "The Impact of Heat Exchangers’ Constructions on the Melting and Solidification Time of Phase Change Materials" *Energies* 13, no. 18: 4840.
https://doi.org/10.3390/en13184840