Short-period thermal cyclic test device for large volumes of microencapsulated phase change materials using a Venturi injector

doi:10.1016/j.est.2021.103223

Journal of Energy Storage

Volume 43, November 2021, 103223

https://doi.org/10.1016/j.est.2021.103223 Get rights and content

Highlights

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A new type of short-period MPCM thermal cyclic test device is reported.
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Device improves heat exchanger rate by pumping MPCM slurry to Venturi injector.
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Optimal operation conditions were 25wt% MPCM slurry with 5 L/min flow rate.
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Prototype tested 5000 thermal cycles with 1 kg of MPCM and 47 s thermal cycle-period.
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Results show MPCM recovery rate was 96% without physical damage.

Abstract

Microencapsulated phase change material (MPCM), which has a large amount of heat capacity during phase change, has been used as a thermal storage medium as a building composite material. MPCM is broken by heat-induced volume changes, and hence, thermal cyclic tests must be performed to estimate their durability. Existing methods for thermal cyclic testing have limitations such as few samples that can be tested or long duration of test. This paper proposes a thermal cyclic test device with a Venturi injector designed to test a large number of samples rapidly. Results of the detailed tests on the pressure and flow rate change of the Venturi tube and the reliability assessment of the developed equipment are presented. MPCM slurry can be transported with up to 25% mass concentration of MPCM at a flow rate of 5 LPM. At 25wt%, MPCM slurry could change 100% of its phase within a straight line of a heat exchange pipe length of 0.61 m from 28 to 35 °C. One thermal cycle for 1 kg of MPCM capsules has a duration of 47 s. Finally, a 5000–thermal cycle test of MPCM was carried out, and it showed that using this equipment caused no broken capsules.

Section snippets

1. Introduction

Energy storage technology using phase change material (PCM) enhances energy efficiency by solving the temporal and spatial imbalances between energy supply and demand. A large amount of heat is released or stored during the melting and solidification of the PCM, without any temperature change [1]. Owing to these advantages of PCM, its application has grown gradually in various fields such as space, electronics, solar cooling and solar power plants, photovoltaic electricity systems, preservation

Theoretical background

Density, viscosity, and thermo-physical properties such as thermal conductivity and specific heat are important parameters for the design of MPCM slurry heat exchange systems. The physical properties of the MPCM slurry mainly depend on its mass concentration and MPCM properties. The density of the MPCM slurry depends on the MPCMs and carrier fluids such as water. The density of the MPCM slurry can be calculated using the following equation [23]: $ρ_{b} = \frac{ρ_{p} \cdot ρ_{f}}{w \cdot ρ_{f} + (1 - w) \cdot ρ_{p}}$ where w is the mass

Materials

The core material of the MPCM used in this study was n-octadecane (CH₃(CH₂)₁₆CH₃) and the shell material was polymethyl methacrylate (PMMA). n-octadecane is a paraffin-type substance with a melting temperature of 28 °C. The paraffin type of PCM has stable chemical and thermal properties and is of low cost, making it one of the most preferred core materials [24]. PMMA was used as the shell material owing to its good mechanical properties and for the protection of the environment [26]. The MPCM

Performance test of venturi injector

Depending on the pressure and flow rate at the inlet, the Venturi injector shows variations in the generated low pressure at its divergent structures. Because the injection flow rate depends on the intensity of the generated low pressure, the experiment must be carried out based on the pressure and flow rate of the Venturi inlet. The pressure at each part of the Venturi injector was measured at various inlet flow rates and pressure conditions. The pressure and flow rates are dependent

Conclusion

The thermal durability of an MPCM capsule is very important to enable its use in building materials or heat transfer fluids. Thermal cyclic tests are generally conducted to verify the durability of the MPCM capsules prior to being used as a building material. The traditional approach for the thermal cyclic test was conducted using DSC, which has good thermal conductivity, but only a small number of samples can be tested. A reliable device was needed to test faster and a larger number of

CRediT authorship contribution statement

Sunuk Kim: Writing – original draft, Investigation, Methodology, Validation, Data curation. Dong Ho Shin: Conceptualization, Investigation, Methodology, Validation. Youngyun Jung: Data curation. Han Seo Ko: Writing – review & editing, Supervision. Youhwan Shin: Writing – review & editing, Project administration, Supervision, Funding acquisition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

Funding: This work was supported by the Korea Institutes of Science and Technology [grant number 2E31234].

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Short-period thermal cyclic test device for large volumes of microencapsulated phase change materials using a Venturi injector

Highlights

Abstract

Section snippets

1. Introduction

Theoretical background

Materials

Performance test of venturi injector

Conclusion

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgments

Energy Convers. Manag.

Renew. Sustain. Energy Rev.

Renew. Sustain. Energy Rev.

Energy

Appl. Therm. Eng.

Appl. Therm. Eng.

Exp. Therm. Fluid Sci.

Int. J. Multiph. Flow

Renew. Sustain. Energy Rev.

Energy Build.

Energy Build.

Nano Struct. Nano Objects

Sol. Energy

Energy Convers. Manag.

Appl. Energy

Cem. Concr. Res.