An experimental study of freezing and melting of water inside spherical capsules used in thermal energy storage systems

Abstract This paper reports the results of an experimental study on the heat transfer during freezing (charging) and melting (discharging) of water inside a spherical capsule of the type often found in the beds of thermal (ice) storage systems used for the building air conditioning systems. Spherical capsules of different diameters and materials are tested. The aqueous solution of 35-wt% ethylene glycol is used as the heat transfer fluid (HTF). The major studied parameters are the size and material of the spherical capsule, the volume flow rate and temperature of the heat transfer fluid (HTF). The effects of these parameters on the time for complete charging/discharging, the solidified/melted mass fraction, the charging/discharging rate, the energy stored/regain, and the energy recovery ratio (ERR) are studied. The experimental results show that the energy recovery ratio is becoming better when using metallic capsules, increasing the capsule size and reducing the HTF volume flow rates.

[1]  Kambiz Vafai,et al.  Thermal charging and discharging of sensible and latent heat storage packed beds , 1991 .

[2]  K. Ismail,et al.  A parametric study on possible fixed bed models for pcm and sensible heat storage , 1999 .

[3]  Liwu Fan,et al.  Experimental and computational study of constrained melting of phase change materials (PCM) inside a spherical capsule , 2009 .

[4]  Ibrahim Dincer,et al.  Thermal modeling of a packed bed thermal energy storage system during charging , 2009 .

[5]  S. Iniyan,et al.  Experimental and analytical investigation of solidification and melting characteristics of PCMs inside cylindrical encapsulation , 2008 .

[6]  D. E. Beasley,et al.  Thermal response of a packed bed of spheres containing a phase-change material , 1989 .

[7]  I. Eames,et al.  Freezing and melting of water in spherical enclosures of the type used in thermal (ice) storage systems , 2002 .

[8]  Robert A. Rapp,et al.  Modeling of fixed bed heat storage units utilizing phase change materials , 1987 .

[9]  Y.-Z. Chen,et al.  Thermal effect of surface tension on the inward solidification of spheres , 2002 .

[10]  Jay M. Khodadadi,et al.  Effects of buoyancy-driven convection on melting within spherical containers , 2001 .

[11]  R. Velraj,et al.  Heat transfer and parametric studies of an encapsulated phase change material based cool thermal energy storage system , 2006 .

[12]  Kamal Abdel Radi Ismail,et al.  A parametric study on ice formation inside a spherical capsule , 2003 .

[13]  Ibrahim Dincer,et al.  Numerical heat transfer analysis of encapsulated ice thermal energy storage system with variable heat transfer coefficient in downstream , 2009 .

[14]  Kamal Abdel Radi Ismail,et al.  Solidification of pcm inside a spherical capsule , 2000 .

[15]  Eun-Pil Kim,et al.  Experimental study on freezing of water with supercooled region in a horizontal cylinder , 2001 .

[16]  Tarik Kousksou,et al.  Dynamic modelling of the storage of an encapsulated ice tank , 2005 .

[17]  I. Dincer,et al.  Performance assessment of some ice TES systems , 2009 .