Energies

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15 pages, 4627 KiB

Open AccessArticle

An Experimental Investigation on the Size Distribution of Snow Particles during Artificial Snow Making

by Wei Zhao, Zheng Li, Hua Zhang, Mingxu Su, Zhenzhen Liu, Pengju Chen and Yaqian Han

Energies 2023, 16(21), 7276; https://doi.org/10.3390/en16217276 - 26 Oct 2023

Cited by 1 | Viewed by 2029

For artificial snowfall, snow particle size can have a direct impact on snow quality. The operating conditions of the snow-makers and environmental factors will influence the atomization and crystallization processes of artificial snow making, which consequently affect snow particle size. This paper investigates [...] Read more.

For artificial snowfall, snow particle size can have a direct impact on snow quality. The operating conditions of the snow-makers and environmental factors will influence the atomization and crystallization processes of artificial snow making, which consequently affect snow particle size. This paper investigates the size distribution of snow particles during artificial snow making under different operating conditions and environmental parameters. For this purpose, an environmental chamber is designed and structured. The laser scattering method was used to measure the size distribution of snow under different parameters in the room. The results show that the distribution of snow crystal particle size aligns closely with the Rosin–Rammler (R-R) distribution. The higher the height of the snowfall, the longer the snow crystals grow and the larger the snow crystal particle size. It has been found that a higher air pressure favors atomization, while the opposite is true for water pressure, which results in a higher air–water pressure ratio, producing smaller snow particle sizes. Additionally, an ambient temperature in the range of −5 °C to −15 °C contributes to the snow crystal form transforming from plates to columns and then back to plates; the snow particle size first decreases and then increases. Snow crystal particles at −10 °C have the smallest size. Outdoor snow-makers should be operated at the highest possible air–water pressure ratio and snow height, and at a suitable ambient temperature. Full article

(This article belongs to the Special Issue Phase Change Materials: The Ideal Solution for Thermal Management)

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24 pages, 10466 KiB

Open AccessArticle

Thermal Performance Analysis of Composite Phase Change Material of Myristic Acid-Expanded Graphite in Spherical Thermal Energy Storage Unit

by Ji Li, Weiqing Wang, Yimin Deng, Long Gao, Junchao Bai, Lei Xu, Jun Chen and Zhi Yuan

Energies 2023, 16(11), 4527; https://doi.org/10.3390/en16114527 - 5 Jun 2023

Cited by 7 | Viewed by 1956

Abstract

In order to improve energy storage efficiency and promote the early achievement of global carbon neutrality goals, this paper proposes a spherical thermal storage unit filled with a composite phase change material (CPCM) comprising myristic acid (MA) and expanded graphite (EG). The effects [...] Read more.

In order to improve energy storage efficiency and promote the early achievement of global carbon neutrality goals, this paper proposes a spherical thermal storage unit filled with a composite phase change material (CPCM) comprising myristic acid (MA) and expanded graphite (EG). The effects of EG content and Stefan number (Ste) on the melting performance were investigated through a combination of experiments and numerical simulations. The results show that an increase in EG content (especially for ≥4 wt.% EG) leads to a temperature profile that assumes a concentric ring shape, while the melting rate increases with an increase in both the EG mass fraction and the Ste number. Compared to pure MA, the time required to complete melting was reduced by 82.2%, 85.6%, and 88.0% at EG contents of 4 wt.%, 5 wt.%, and 6 wt.%, respectively. Notably, the Ste value has a greater effect on melting when the EG content is ≤3 wt.%. The optimal EG content in the spherical cell was determined to be 4 wt.%, and a dimensionless analysis established a general correlation between the liquid mass fraction and the Fo, Ste, and Gr numbers. Full article

(This article belongs to the Special Issue Phase Change Materials: The Ideal Solution for Thermal Management)

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13 pages, 4171 KiB

Open AccessArticle

A Low-Density Polyethylene-Reinforced Ternary Phase-Change Composite with High Thermal Conductivity for Battery Thermal Management

by Yueliang Yu, Hongmei Qin, Shusen Ran, Jinhui Song, Wenlai Xia, Shan Wang and Chuanxi Xiong

Energies 2023, 16(9), 3838; https://doi.org/10.3390/en16093838 - 29 Apr 2023

Cited by 3 | Viewed by 2215

Abstract

Paraffin phase change materials (PCMs) exhibit great potential in battery thermal management (BTM); nevertheless, their application has been hampered by the handicap of low thermal conductivity, leakage, and volume expansion during phase transition. In this work, ternary composite PCMs formed of paraffin, expanded [...] Read more.

Paraffin phase change materials (PCMs) exhibit great potential in battery thermal management (BTM); nevertheless, their application has been hampered by the handicap of low thermal conductivity, leakage, and volume expansion during phase transition. In this work, ternary composite PCMs formed of paraffin, expanded graphite (EG), and low-density polyethylene (LDPE) were developed for application in BTM. The structure and properties of the composite PCMs were characterized via X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, and thermal constant analysis. The result shows that EG can form a large-size graphite frame as heat conduction paths to improve the thermal conductivity of the composite PCM, and LDPE can form an interpenetrating network within the composite PCM to resist the internal stress of paraffin expansion and prevent deformation. The latent heat and thermal conductivity of the composite PCMs loaded with 10 wt% EG and 4 wt% LDPE can reach 172.06 J/g and 3.85 Wm⁻¹K⁻¹ with a relatively low leakage ratio of 6.2 wt%. Remarkably, the composite PCMs could reduce the temperature rise of the battery by 55.1%. In brief, this work provides a feasible route to develop high-performance PCMs for BTM. Full article

(This article belongs to the Special Issue Phase Change Materials: The Ideal Solution for Thermal Management)

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15 pages, 7894 KiB

Open AccessArticle

Influence of Copper Foam on the Thermal Characteristics of Phase Change Materials

by Xiaokuan You, Xiangxin Sun, Jie Huang, Zilong Wang and Hua Zhang

Energies 2023, 16(4), 1994; https://doi.org/10.3390/en16041994 - 17 Feb 2023

Cited by 3 | Viewed by 2402

Abstract

The phase change material is a hot research topic in solar thermal storage systems. However, the thermal conductivity of pure phase change materials is usually low, which hinders its application in facilities. In this study, copper foam is used to increase the thermal [...] Read more.

The phase change material is a hot research topic in solar thermal storage systems. However, the thermal conductivity of pure phase change materials is usually low, which hinders its application in facilities. In this study, copper foam is used to increase the thermal characteristics of the paraffin. Simulations are conducted to compare the melting characteristics of the pure paraffin and the paraffin/copper foam composite phase change material. A visualized experimental device was designed and built, and the copper foam composite phase change material, with a volume fraction of 15%, was prepared by filling part of the copper foam in the phase change material. The simulation results agree well with the experimental results. The root mean square errors of the temperature for the pure paraffin and the composite phase change material are 0.0223 and 0.0179, respectively. The experimental results show that the copper foam can enhance thermal conductivity and decrease melting time. It takes 870 s for the composite phase change material to melt, which is 3.44% less than that of the pure paraffin. This study deepens the understanding of the composite phase change material and provides a reference for the design of thermal energy storage devices. Full article

(This article belongs to the Special Issue Phase Change Materials: The Ideal Solution for Thermal Management)

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14 pages, 3979 KiB

Open AccessArticle

An Experimental Investigation on the Performance of a Water Storage Tank with Sodium Acetate Trihydrate

by Jie Huang, Fei Xu, Zilong Wang and Hua Zhang

Energies 2023, 16(2), 777; https://doi.org/10.3390/en16020777 - 9 Jan 2023

Cited by 2 | Viewed by 2013

Abstract

Phase change material (PCM) water tanks have a major influence on the efficiency improvement of solar energy systems. This article discusses the effects of PCM under various inlets in a tank based on related research. So as to research the performance of the [...] Read more.

Phase change material (PCM) water tanks have a major influence on the efficiency improvement of solar energy systems. This article discusses the effects of PCM under various inlets in a tank based on related research. So as to research the performance of the water storage tank, this paper built a set of water tank experimental systems using sodium acetate trihydrate. The thermal characteristics of two different water tanks were analyzed at 2, 6 and 10 L/min when the inlet temperature was 20 °C and the initial high temperature was 80 °C. The test results indicate that adding PCMs helps to provide an extra 1.4% of stored heat, prolong the hot water outlet time, and has a better thermal stratification, compared with ordinary water tanks. However, PCMs do not give off heat quickly at high flow rates. Besides the exergy efficiency (EE) gradually decreasing, the MIX number first decreases and then increases; the fill efficiency (FE) has the opposite trend with the flow increasing. FE has a max of 0.905 at 6 L/min. Full article

(This article belongs to the Special Issue Phase Change Materials: The Ideal Solution for Thermal Management)

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14 pages, 2414 KiB

Open AccessArticle

Simulation Study on the Performance of an Enhanced Vapor-Injection Heat-Pump Drying System

by Suiju Dong, Yin Liu, Zhaofeng Meng, Saina Zhai, Ke Hu, Fan Zhang and Dong Zhou

Energies 2022, 15(24), 9542; https://doi.org/10.3390/en15249542 - 15 Dec 2022

Cited by 1 | Viewed by 2149

Abstract

The performance of an enhanced vapor-injection heat-pump drying system was designed and theoretically studied in cold areas. According to the simulation findings, the ideal vapor-injection charge of the system ranges from 12.3 to 13.9%, and its ideal intermediate pressure is between 1.278 and [...] Read more.

The performance of an enhanced vapor-injection heat-pump drying system was designed and theoretically studied in cold areas. According to the simulation findings, the ideal vapor-injection charge of the system ranges from 12.3 to 13.9%, and its ideal intermediate pressure is between 1.278 and 1.498 MPa when the evaporation temperature is above 0 °C. The ideal vapor-injection charge of the system ranges from 13 to 20%, and its optimal intermediate pressure ranges from 1.078 to 1.278 MPa when the evaporation temperature is −15–0 °C. The ideal vapor-injection charge of the system ranges from 20 to 24%, and the intermediate pressure ranges from 0.898 to 1.078 MPa when the evaporation temperature is below −15 °C. The heat and humidity exhausted air source heat-pump drying (HHE–ASHPD) system has higher dehumidification efficiency than the closed heat-pump drying (CHPD) system under the same air temperature, humidity, and volume parameters. Full article

(This article belongs to the Special Issue Phase Change Materials: The Ideal Solution for Thermal Management)

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15 pages, 3955 KiB

Open AccessArticle

Experimental Performance Study of Solar-Assisted Enhanced Vapor Injection Air-Source Heat Pump System

by Zhengrong Li, Yongheng Du, Yuqin Pan, Fan Zhang, Zhaofeng Meng and Yanan Zhang

Energies 2022, 15(20), 7730; https://doi.org/10.3390/en15207730 - 19 Oct 2022

Cited by 3 | Viewed by 1784

Abstract

In this paper, a solar-assisted enhanced vapor injection air-source heat pump (SC-EVIHP) system was built to investigate its heating performance in cold regions. A typical-weather day in Harbin was selected for the experiment, and the heating characteristics of the SC-EVIHP system were explored [...] Read more.

In this paper, a solar-assisted enhanced vapor injection air-source heat pump (SC-EVIHP) system was built to investigate its heating performance in cold regions. A typical-weather day in Harbin was selected for the experiment, and the heating characteristics of the SC-EVIHP system were explored under variable working conditions. The experimental results showed that the system was greatly affected by solar radiation intensity. On typical-weather days in winter, the maximum values for the heating capacity and COP of the system appeared at the time of maximum radiation intensity. Compared with conventional enhanced vapor injection air-source heat pump systems (EVI-ASHPs), the heating capacity and COP were increased by 24.9% and 12.5% at most, respectively. The COP of the system increased by at most 11.1% under conditions where the outdoor temperature was −12 °C and the outlet hot air temperature of the solar air collector was 40 °C. The SC-EVIHP system works well in a low-temperature environment and can be widely applied in cold regions. Full article

(This article belongs to the Special Issue Phase Change Materials: The Ideal Solution for Thermal Management)

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24 pages, 5227 KiB

Open AccessArticle

Life Cycle Assessment of Dispersed Phase Change Material Heat Accumulators for Cooperation with Buildings in the District Heating System

by Michał Turski and Agnieszka Jachura

Energies 2022, 15(16), 5771; https://doi.org/10.3390/en15165771 - 9 Aug 2022

Cited by 8 | Viewed by 3103

Abstract

The wide use of energy-efficient district heating systems allows for decreased atmospheric pollution resulting from lower emissions. One of the ways to increase the efficiency of existing district heating systems, and a key element of new systems using renewable energy sources, is modern [...] Read more.

The wide use of energy-efficient district heating systems allows for decreased atmospheric pollution resulting from lower emissions. One of the ways to increase the efficiency of existing district heating systems, and a key element of new systems using renewable energy sources, is modern heat storage technology—the utilization of dispersed PCM heat accumulators. However, the use of different solutions and the inconsistency of selection methods make it difficult to compare the obtained results. Therefore, in this paper, using TRNSYS software, a standardization of the selection of dispersed PCM heat accumulators for cooperation with buildings in the DHS was proposed along with a Life Cycle Assessment. Life Cycle Assessment could be a good, versatile indicator for new developments in district heating systems. A new contribution to the research topic was the Life Cycle Assessment itself as well as the range of heat output of the substations up to 2000 kW and the development of nomograms and unitary values for the selection of individual parameters based on the relative amount of heat uncollected by buildings. The technical potential of heat storage value, %ΔQ_i_,st, was from 49.4% to 59.6% of the theoretical potential of heat storage. The increases in the active volume of the PCM heat accumulator, dV_PCM, and the mass of the required amount of PCM, dm_st, were, respectively, 0.8 × 10⁻²–4.0 m³/kW and 1.3–6.7 × 10⁻² kg/kW. Due to dispersed heat storage, an increase in system efficiency of 41% was achieved. LCA analysis showed that a positive impact on the environment was achieved, expressed as negative values of the Eco-indicator from −0.504 × 10⁻² to −6.44 × 10⁻² kPt/kW. Full article

(This article belongs to the Special Issue Phase Change Materials: The Ideal Solution for Thermal Management)

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