Energy Storage in a Technical Grade Phase Change Material in a Horizontal Double Pipe Heat Exchanger: Part-I

Abstract

A tran,sient hvo-tlintensional numerical model was developed to investigcLte the melting characteristics oJ an impure phase-chcltge material (PCM) ewbedcled betv,een tw,o concentric circular horizontal cylinder.s. The mocleled transport equations were suitably non-dimensionalizecl and v)ere solvecl numericall,v in its primitive variables .form on a staggered grid arrangement employing q control-yolume /inite tlilference method. The selectecl PCM melts oyer a temperature range. To easily account the latter aspect in. the model, cm enthalpl;-porosity bctsed .firecl grid scheme tras used to solye the t:onvec:tion-dffision utrshlt region phase r:hange problem. The inner cylindrical tube v'crs lteated to a constont temperatL-rre by o lteat trans/br Jluicl while the outer tube tuas instrlated. Time+vise eyolutions o.f the teruperature distribtnions are pre,sented. Vorious quantities such as, the average lt{usselt nnmher over the inner tthe strfiace, the total meltJraction, ancl the tcttql cumulatiye stored energ,v, all as ofunction oJ the melting time are reported.for three inner wall temperatures and ./br an initially saturated solid PCM and also./or a sub-cooled conclitictn of 10"C ol'the PCM. The preclicted restilts shoy: tlta.t the melting rate increases rctpidly up to the melting time oJ.about 4I .I 8 ruin. AJier this time the melting rate increases but at a considerabllt slower rate. The ,\torage of thermal energ)., increases with the increase of'the inner wall temperature and initial temperahtre o;f the solicl PCM. The energ)) charged is greatly irfluenced by the change oJ'the inner tube w,all temperature compared to the change of the initial solicl PCIII temperature.