# Macro-Encapsulated PCM Cylinder Module Based on Paraffin and Float Stones

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Experimental

#### 2.1. The Used PCM

#### 2.2. Improvement of the Comprehensive Thermal Conductivity

^{−1}·K

^{−1}. Being the same as other organic PCM, this will definitely hinder the thermal charging and discharging rates of the PCM. Instead of relatively expensive materials like expanded graphite, sulfonated grapheme, and metal materials, we used float stones to improve the thermal conductivity of the PCM. They were immersed in the melted PCM in a cylinder for a day to make the liquid PCM fully occupy its porous structure. Experimental float stones were from a company in Dalian, China. Detailed information can be achieved from the material sheet of the supplier. The constituents of the selected float stone is presented in Table 1. The density for the float stone is 520 Kg/m

^{3}, porosity $\phi $ = 50%, and thermal conductivity is 0.326 W·m

^{−1}·K

^{−1}.

^{−1}·K

^{−1}. The thermal conductivity of the composite PCM is assessed to be 0.72 W·m

^{−1}·K

^{−1}. The whole module is composed of the composite PCM area and single PCM area. Consequently, the PCM module can be seen as composite PCM granules dispersed in PCM. Then, it is able to obtain ${\lambda}_{\mathrm{equ}}$ by using Equation (3) [25], where ${\psi}_{\text{p}}$ is the volume ratio of composite PCM granules to the whole volume, and S is a structural parameter:

^{−1}·K

^{−1}. Adding in float stones make the thermal conductivity of the thermal storage medium increase by 126%. There are also disadvantages for using float stones. Fewer PCM was contained in the PCM cylinder module and the latent heat loss is considerable (25.0%). The volume of PCM occupies 75.8% of the whole space and the comprehensive latent heat is 105.1 KJ/Kg. The used float stones and the immersed composite PCM is shown in Figure 2.

#### 2.3. Preparation of the PCM Cylinder Module

#### 2.4. Test Arrangement

## 3. Numerical Simulations

#### 3.1. Governing Equations

_{mush}is a constant for fuzzy zone of liquid and solid state; ν is the implicated speed.

#### 3.2. Model in the CFD Software

#### 3.3. Boundary and Initial Conditions

## 4. Results and Discussion

#### 4.1. Microstructure Analyses and Leakage Analysis

#### 4.2. Validation of the Simulation

#### 4.3. Simulation Cases of Different Cylinder Diameters with Float Stones

#### 4.4. Experimental Cases with and without Float Stones

## 5. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 2.**The used float stones and the immersed composite PCM: (

**a**) float stones, and (

**b**) immersed composite PCM.

**Figure 3.**The produced container and PCM cylinder modules: (

**a**) PET plastic container; (

**b**) module without float stones; (

**c**) module with float stones.

**Figure 6.**SEM pictures of the float stones and composite PCM: (

**a**) float stones; and (

**b**) float stones immersed by PCM.

**Figure 7.**Simulated melting process of PCM cylinder modules (diameter is 40 mm, water temperature is 55 °C): (

**a**) 17 min; (

**b**) 34 min; (

**c**) 51 min; (

**d**) 68 min.

**Figure 8.**Experimental and numerical results of middle temperatures of PCM cylinder modules when the diameter is 20 mm.

**Figure 9.**Experimental and numerical results of middle temperatures of PCM cylinder modules when the diameter is 40 mm.

**Figure 10.**PCM cylinder module melting times for different diameters when the hot water temperature is 50 °C.

**Figure 11.**PCM cylinder module melting times for different diameters when the hot water temperature is 55 °C.

**Figure 12.**PCM cylinder module melting times for different diameters when the hot water temperature is 60 °C.

**Figure 13.**Comparison of melting time between PCM cylinder modules with and without float stones when the diameter is 40 mm.

**Figure 14.**Comparison of melting time between PCM cylinder modules with and without float stones when the diameter is 20 mm.

Constituent | SiO_{2} | CaO | MgO | Fe_{2}O_{3} | FeO | Al_{2}O_{3} | TiO_{2} | K_{2}O | Na_{2}O |
---|---|---|---|---|---|---|---|---|---|

Ratio (%) | 53.82 | 8.36 | 2.46 | 9.08 | 1.12 | 16.89 | 0.06 | 2.30 | 2.55 |

Number | Hot Water Temperature | Module Diameter | Remarks |
---|---|---|---|

Number 1 | 55 °C | 20 mm | Each case include PCM cylinder modules with and without float stones. |

Number 2 | 60 °C | 20 mm | |

Number 3 | 55 °C | 40 mm | |

Number 4 | 60 °C | 40 mm |

© 2016 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**

Huang, K.; Liang, D.; Feng, G.; Jiang, M.; Zhu, Y.; Liu, X.; Jiang, B.
Macro-Encapsulated PCM Cylinder Module Based on Paraffin and Float Stones. *Materials* **2016**, *9*, 361.
https://doi.org/10.3390/ma9050361

**AMA Style**

Huang K, Liang D, Feng G, Jiang M, Zhu Y, Liu X, Jiang B.
Macro-Encapsulated PCM Cylinder Module Based on Paraffin and Float Stones. *Materials*. 2016; 9(5):361.
https://doi.org/10.3390/ma9050361

**Chicago/Turabian Style**

Huang, Kailiang, Dong Liang, Guohui Feng, Mingzhi Jiang, Yuhua Zhu, Xin Liu, and Bian Jiang.
2016. "Macro-Encapsulated PCM Cylinder Module Based on Paraffin and Float Stones" *Materials* 9, no. 5: 361.
https://doi.org/10.3390/ma9050361