logo

SCIENCE CHINA Technological Sciences, Volume 60 , Issue 5 : 668-677(2017) https://doi.org/10.1007/s11431-016-9001-x

Thermal performances of non-equidistant helical-coil phase change accumulator for latent heat storage

More info
  • ReceivedDec 1, 2016
  • AcceptedJan 11, 2017
  • PublishedApr 10, 2017

Abstract

Helical-coil is a common structure of heat exchanger unit in phase change heat accumulator and usually has the equal coil pitch between adjacent coils. Its thermal performances could be improved by improving the uniformity of the phase change material (PCM) temperature distribution. Thus, a novel non-equidistant helical-coil structure was proposed in this study. Its coil pitch decreased along the flow direction of heat transfer fluid, which made the heat exchange area in unit volume increase to match the decreasing temperature difference between the heat transfer fluid and PCM. The structure was optimized using numerical simulation. An experimental system was developed and the experiment results indicated that the proposed non-equidistant helical-coil heat accumulator was more effective than equidistant helical-coil for latent heat storage. The uniformity of the temperature distribution was also confirmed by simulation results.


Acknowledgment

This work was supported by the National Natural Science Foundation of China (Grant No. 51576187) and Fundamental Research Funds for the Central Universities (Grant No. WK2090130016).


References

[1] Farid M M, Khudhair A M, Razack S A K, et al. A review on phase change energy storage: Materials and applications. Energy Conv Manag, 2004, 45: 1597-1615 CrossRef Google Scholar

[2] Pereira da Cunha J, Eames P. Thermal energy storage for low and medium temperature applications using phase change materials—A review. Appl Energ, 2016, 177: 227-238 CrossRef Google Scholar

[3] Zhang H L, Baeyens J, Degrève J, et al. Latent heat storage with tubular-encapsulated phase change materials (PCMs). Energy, 2014, 76: 66-72 CrossRef Google Scholar

[4] Rathod M K, Banerjee J. Thermal performance enhancement of shell and tube Latent Heat Storage Unit using longitudinal fins. Appl Thermal Eng, 2015, 75: 1084-1092 CrossRef Google Scholar

[5] Jegadheeswaran S, Pohekar S D. Performance enhancement in latent heat thermal storage system: A review. Renew Sust Energ Rev, 2009, 13: 2225-2244 CrossRef Google Scholar

[6] Nomura T, Zhu C, Nan S, et al. High thermal conductivity phase change composite with a metal-stabilized carbon-fiber network. Appl Energ, 2016, 179: 1-6 CrossRef Google Scholar

[7] Xu B, Li Z. Paraffin/diatomite composite phase change material incorporated cement-based composite for thermal energy storage. Appl Energ, 2013, 105: 229-237 CrossRef Google Scholar

[8] Zhao C Y, Wu Z G. Heat transfer enhancement of high temperature thermal energy storage using metal foams and expanded graphite. Sol Energ Mater Sol Cells, 2011, 95: 636-643 CrossRef Google Scholar

[9] Li M. A nano-graphite/paraffin phase change material with high thermal conductivity. Appl Energ, 2013, 106: 25-30 CrossRef Google Scholar

[10] Huang Z, Gao X, Xu T, et al. Thermal property measurement and heat storage analysis of LiNO3/KCl—Expanded graphite composite phase change material. Appl Energ, 2014, 115: 265-271 CrossRef Google Scholar

[11] Xiao X, Zhang P, Li M. Preparation and thermal characterization of paraffin/metal foam composite phase change material. Appl Energ, 2013, 112: 1357-1366 CrossRef Google Scholar

[12] Alam T E, Dhau J S, Goswami D Y, et al. Macroencapsulation and characterization of phase change materials for latent heat thermal energy storage systems. Appl Energ, 2015, 154: 92-101 CrossRef Google Scholar

[13] Zhang P, Xiao X, Ma Z W. A review of the composite phase change materials: Fabrication, characterization, mathematical modeling and application to performance enhancement. Appl Energ, 2016, 165: 472-510 CrossRef Google Scholar

[14] Liu L, Su D, Tang Y, et al. Thermal conductivity enhancement of phase change materials for thermal energy storage: A review. Renew Sust Energ Rev, 2016, 62: 305-317 CrossRef Google Scholar

[15] Dzyubenko B V. Influence of flow twisting on convective heat transfer in banks of twisted tubes. Heat Trans Res, 2005, 36: 449-460 CrossRef Google Scholar

[16] Yakimenko R I, Dzyubenko B V. Efficiency of heat transfer surfaces using the method of effective parameters. Heat Trans Res, 2001, 32: 8 CrossRef Google Scholar

[17] Tay N H S, Belusko M, Castell A, et al. An effectiveness-NTU technique for characterising a finned tubes PCM system using a CFD model. Appl Energ, 2014, 131: 377-385 CrossRef Google Scholar

[18] Lamberg P. Approximate analytical model for two-phase solidification problem in a finned phase-change material storage. Appl Energ, 2004, 77: 131-152 CrossRef Google Scholar

[19] Velraj R, Seeniraj R V, Hafner B, et al. Experimental analysis and numerical modelling of inward solidification on a finned vertical tube for a latent heat storage unit. Sol Energ, 1997, 60: 281-290 CrossRef Google Scholar

[20] Castell A, Solé C, Medrano M, et al. Natural convection heat transfer coefficients in phase change material (PCM) modules with external vertical fins. Appl Thermal Eng, 2008, 28: 1676-1686 CrossRef Google Scholar

[21] Li Y Q, He Y L, Song H J, et al. Numerical analysis and parameters optimization of shell-and-tube heat storage unit using three phase change materials. Renew Energ, 2013, 59: 92-99 CrossRef Google Scholar

[22] Li W, Kong C C. Numerical study on the thermal performance of a shell and tube phase change heat storage unit during melting process. Adv Mech Eng, 2014, 6: 360283 CrossRef Google Scholar

[23] Mao Q, Zhang L, Wu H, et al. Design and calculation of a new storage tank for concentrating solar power plant. Energy Conv Manag, 2015, 100: 414-418 CrossRef Google Scholar

[24] Agyenim F, Hewitt N, Eames P, et al. A review of materials, heat transfer and phase change problem formulation for latent heat thermal energy storage systems (LHTESS). Renew Sust Energ Rev, 2010, 14: 615-628 CrossRef Google Scholar

[25] Mori Y, Nakayama W. Study on forced convective heat transfer in curved pipes. Int J Heat Mass Transfer, 1967, 10: 681-695 CrossRef Google Scholar

[26] Guo Z Y, Zhou S Q, Li Z X, et al. Theoretical analysis and experimental confirmation of the uniformity principle of temperature difference field in heat exchanger. Int J Heat Mass Transfer, 2002, 45: 2119-2127 CrossRef Google Scholar

[27] Shan R K, Joshi S D. Handbook of Single-Phase Convective Heat Transfer (Chapter 5). New York: Wiley-Interscience, 1987. Google Scholar

[28] Nomura T, Tsubota M, Oya T, et al. Heat storage in direct-contact heat exchanger with phase change material. Appl Thermal Eng, 2013, 50: 26-34 CrossRef Google Scholar

[29] Colella F, Sciacovelli A, Verda V. Numerical analysis of a medium scale latent energy storage unit for district heating systems. Energy, 2012, 45: 397-406 CrossRef Google Scholar

[30] Lorente S, Bejan A, Niu J L. Phase change heat storage in an enclosure with vertical pipe in the center. Int J Heat Mass Transfer, 2014, 72: 329-335 CrossRef Google Scholar

[31] Zipf V, Neuhäuser A, Willert D, et al. High temperature latent heat storage with a screw heat exchanger: Design of prototype. Appl Energ, 2013, 109: 462-469 CrossRef Google Scholar

[32] Li M, Wu Z, Tan J. Heat storage properties of the cement mortar incorporated with composite phase change material. Appl Energ, 2013, 103: 393-399 CrossRef Google Scholar

[33] Rathod M K, Banerjee J. Experimental investigations on latent heat storage unit using paraffin wax as phase change material. Exp Heat Transfer, 2014, 27: 40-55 CrossRef Google Scholar

  • Figure 1

    (Color online) Schematic diagram of the helical-coil phase change heat accumulator.

  • Figure 2

    Variation of the temperature difference and the heat transfer area per length during the charging process.

  • Figure 3

    Liquid fraction of different helical-coil tubes with different coil number proportion.

  • Figure 4

    Grid of the helical-coil heat accumulator used for the simulations.

  • Figure 5

    Comparisons of the outlet temperature and the liquid fraction obtained from the two grids. (a) Outlet temperature; (b) liquid fraction.

  • Figure 6

    Comparisons of the temperature distribution between the equidistant helical-coil phase change heat accumulator and the non-equidistant one in the simulation.

  • Figure 7

    Comparison of the heat storage capacity between the equidistant helical-coil phase change heat accumulator (unoptimized) and the non-equidistant one (optimized) in the simulation.

  • Figure 8

    (Color online) Main structure of the experimental system.

  • Figure 9

    (Color online) Locations of the thermocouples and the structures of the equidistant and non-equidistant helical-coil phase change heat accumulator.

  • Figure 10

    Comparison of the structure between these two kinds of helical-coil tube. (a) Equidistant helical-coil tube; (b) non-equidistant helical-coil tube.

  • Figure 11

    Temperature variation of the equidistant heat accumulator (a) and the non-equidistant heat accumulator (b).

  • Figure 12

    Temperature distributions of the two kinds of the helical-coil heat accumulator and comparison of heat storage capacity.

  • Table 1   Thermophysical properties of the paraffin in this study

    Thermophysical properties

    Value

    Density ρ (kg/m3)

    800

    Thermal conductivity k (W/(m K))

    0.2

    Heat capacity cp (kJ/(kg K))

    1.25

    Dynamic viscosity μ (Pa S)

    0.008

    Latent heat Q (J/kg)

    12500

    Thermal expansion coefficient (K−1)

    0.002

  • Table 2   Locations of the thermocouples (unit: cm)

    Thermocouple

    Location

    Thermocouple

    Location

    Thermocouple

    Location

    T1

    (3,27)

    T6

    (5,27)

    T11

    Inlet

    T2

    (3,21)

    T7

    (5,21)

    T12

    Outlet

    T3

    (3,15)

    T8

    (5,15)

    T4

    (3.9)

    T9

    (5,9)

    T5

    (3,3)

    T10

    (5,3)

  • Table 3   Different kinds of working conditions

    Temperature of the hot fluid (°C)

    Flow rate of the hot fluid (L/h)

    70

    20

    30

    40

    75

    20

    30

    40

    80

    20

    30

    40

  • Table 4   Degree of the optimization

    Flow rate L/h

    T(°C)

    70

    75

    80

    20

    68.2%

    30.5%

    28.6%

    30

    59.1%

    24.0%

    15.4%

    40

    27.0%

    20.6%

    12.0%

Copyright 2020 Science China Press Co., Ltd. 《中国科学》杂志社有限责任公司 版权所有

京ICP备17057255号       京公网安备11010102003388号