Preparation and properties of pentadecane microcapsule latent heat functional fluid

doi:10.19799/j.cnki.2095-4239.2022.0229

Abstract

Abstract:

To prevent the leakage of materials during the phase-change process, low-temperature phase-change microcapsules with pentadecane (Pen) as the core material and urea-formaldehyde resin (UF) as the wall material were prepared using insitu polymerization. The effect of heating rate, polymerization pH, and polymerization speed on the microcapsules preparation was studied. The morphology, chemical composition, thermodynamic properties, and the particle-size distribution of microcapsules were tested using SEM, FT-IR, DSC, and Malvern laser particle-size analyzer. A heating rate of 1.0 ℃/min, polymerization pH value of 3.5, and polymerization speed of 500 r/min are the optimal preparation conditions for pentadecane microcapsules. The microcapsules prepared under the above conditions have spherical morphology, smooth surface, a few UF particle adherence, and the particle-size distribution is uniform. The phase-change temperature and latent heat of the microcapsules are 8.20 ℃ and 115.3 J/g, respectively. The average particle size of the microcapsules is 50.0 μm, and the encapsulation rate reaches 77.3%. The experimental results show that the core and wall materials are held by physical forces. The microcapsules have good heat storage performance and thermal stability. Pentadecane microcapsules are dispersed with different mass fractions of ethanol solution as the base solution. A stable latent-heat functional fluid (LHFF) is obtained using a static experiment for 24 h. The LHFF is the most stable in the base solution with 70 wt% ethanol. The thermal conductivity and viscosity of the LHFF are tested and analyzed using a thermal conductivity tester and rotational viscometer. The thermal conductivity of the LHFF increases with an increase in temperature and decreases with an increase in the mass fraction of microcapsules. The viscosity of the LHFF decreases with an increase in temperature and increases with an increase in the mass fraction of microcapsules. As the secondary refrigerant of the air conditioning system, LHFF can improve the performance of the refrigeration unit, reduce the energy consumption of the pump, and improve the economy of cold storage of the air conditioning system.

Key words: pentadecane, phase change materials, microcapsules, in situ polymerization, latent heat functional fluids, phase change enthalpy

CLC Number:

TK 02

Yanghui CHANG, Zhigao SUN. Preparation and properties of pentadecane microcapsule latent heat functional fluid[J]. Energy Storage Science and Technology, 2022, 11(10): 3123-3132.

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试剂名称	纯度	生产厂家
尿素	≥99.0%	无锡市晶科化工有限公司
甲醛溶液	≥37.0%	上海联式化工试剂有限公司
三乙醇胺	≥98.0%	天津市恒兴化学试剂制造有限公司
十五烷	≥98.0%	上海阿拉丁生化科技股份有限公司
十二烷基硫酸钠(SDS)	≥98.0%	国药集团化学试剂有限公司
间苯二酚	≥99.0%	上海阿拉丁生化科技股份有限公司
氯化铵	≥99.5%	天津市致远化学试剂有限公司
冰乙酸	≥99.7%	上海阿拉丁生化科技股份有限公司
正辛醇	≥98.0%	天津博迪化工股份有限公司
无水乙醇	≥99.8%	无锡市晶科化工有限公司
去离子水	—	自制

仪器名称	型号	性能参数	厂家
电子天平	BSA224S	0～220 g，±0.01 mg	赛多利斯有限公司
数控超声波清洗器	KQ-100DE	功率100 W	昆山市超声仪器有限公司
电动搅拌器	JJ-1	0～2000 r/min	常州市西城新瑞仪器厂
循环水真空泵	SHZ-D(Ⅲ) ABS	-0.1～0 MPa	上海力辰邦西仪器有限公司
扫描电子显微镜(能谱)	Quanta FEG 250	放大倍数:14×～1 000 000×	美国FEI公司
鼓风干燥箱	DHG-9070A	RT+10～100 ℃	上海精宏实验设备有限公司
台式酸度计	pHS-3C	精度±0.05	上海仪电科学仪器有限公司
均质乳化机	XFJ300-S	100～20000 r/min	上海标本模型厂
差热热重联用仪	SDT2960	精度±0.001 ℃	美国TA公司
差示扫描量热仪	DSC2500	精度±0.05 ℃	美国TA公司
激光粒度仪	Mastersizer 3000	测试范围0.01～3 000 μm	英国马尔文仪器有限公司
旋转黏度计	NDJ-79	1～1×10⁶mPa·s	上海精密仪器仪表有限公司
导热系数测定仪	DRE-Ⅲ	0.001～100 W/(m·K)	湘潭湘仪仪器有限公司
低温恒温水槽	THD-2015	温控范围-20～99 ℃	宁波天恒仪器厂

样品编号	升温速率/(℃/min)	聚合pH值	聚合转速/(r/min)
T₁	0.8	3.5	500
T₂	1.0	3.5	500
T₃	1.4	3.5	500
T₄	1.0	3.0	500
T₅	1.0	4.0	500
T₆	1.0	3.5	300
T₇	1.0	3.5	700

样品名称	凝固温度^①/℃	凝固焓^①/(J/g)	凝固温度^②/℃	凝固焓^②/(J/g)	熔融温度^①/℃	熔融焓^①/(J/g)	熔融温度^②/℃	熔融焓^②/(J/g)	包裹率/%
十五烷	-5.78	37.69	7.34	151.80	-3.86	37.01	8.42	147.70	—
十五烷微胶囊	-8.23	31.29	7.02	112.00	-3.93	30.52	8.20	115.30	77.8

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