Freezing and melting of water in spherical enclosures of the type used in thermal (ice) storage systems Ian W. Eames a, * , Kamel T. Adref b a Department of Architecture, Institute of Building Technology, University of Nottingham, University Park, Nottingham, NG7 2RD, UK b Department of Mechanical Technology, College of Technology at Dammam, P.O. Box 7650, Dammam 31472, Saudi Arabia Received 30 September 2001; accepted 10 December 2001 Abstract This paper describes and evaluates the results of an experimental study aimed at the characterisation of the freezing and melting processes for water contained in spherical elements of the type often found in the beds of thermal (ice) storage systems used building air conditioning systems. The results include semi- empiricalequationsthatallowthemassoficewithinaspheretobepredictedatanytimeduringthefreezing ormeltingprocesses.Itisbelievedthattheseequationswillbeusefulinmodellingthedynamicbehaviourof thermal (ice) storage using spherical elements as phase change. The apparatus, method and results are described. A novel method which was used to measure the water–ice interface position during the freezing processisalsodescribed.Severalinterestingresultswereobtainedfromthisstudy. Ó 2002ElsevierScience Ltd. All rights reserved. Keywords: Energy storage; Latent heat storage; Ice; Melting; Freezing 1. Introduction Animportantaimwhendesigningathermal(ice)storeistoachievehighratesofheattransfer between the heat transfer fluid (HTF) and the encapsulated phase change medium during the meltingandfreezingprocessesastheseeffecttheenergydischargeandchargeratesofastore.For this reason, as well as the growing number of applications of thermal (ice) storage in air cooling systems, researchers have been encouraged to study the heat transfer process involved in the Applied Thermal Engineering 22 (2002) 733–745 www.elsevier.com/locate/apthermeng * Corresponding author. Tel.: +44-115-951-3132; fax: +44-115-951-3159. E-mail address: ian.eames@nottingham.ac.uk (I.W. Eames). 1359-4311/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S1359-4311(02)00026-1