Thermal Storage And Rejection Of Solid Phase-Change Materials

Thermal storage system is an efficient way to solve the matching problem in time and strength between energy supply and consumption and to reduce the environmental pollution. The phase-change thermal storage has larger heat stored density and higher thermal efficiency. It is more compact and easy to be controlled and match with process system as compared with the other thermal stored ways. The phase-change thermal storage gradually becomes a preferred heat stored technique and has a widely applied prospect.In this thesis, the experimental investigations were conducted on the heat stored and rejected performance in the wax thermal storage with coil pipe, the GALISOL Ba(OH)2(8H2O thermal storage, and the packing bed of Pentaerythritol particles. The heat-rejected behaviors of solid-solid phase-change in the packing bed with PG particles were numerically predicted. The remarkably conclusions are drawn as follows.(1) The experimental results for the wax thermal storage with coil pipe shows that in the process of heat stored, the temperature profile in thermal storage becomes more uneven as the increase of heating time. The addition of the copper powder and silicon powder leads to the increase of effective thermal conductivity of wax and makes the temperature profile to become more uniform in the thermal storage. In these wax thermal storages, the one with stainless steel ribbons has the most uniform temperature profile. In the heat-rejected process, the temperature of water at outlet decreases most rapidly for the thermal storage with pure wax, secondly for the one with wax and copper powder, and then for the one with wax and silicon powder. At fixed water flow rate and inlet temperature, the thermal storage with wax and stainless steel ribbons has most water outlet temperature in these thermal storages.(2) The experimental results of the GALISOL thermal storage with Ba(OH)2(8H2O indicates that in the heat-stored stage, the temperatures on the surface of the encapsulation chamber of the phase-change material is uniform and the GALISOL thermal storage can keep high water at the outlet for a longer time. The heat-stored capacity unit volume and the heat-rejected strength of the GALISOL thermal storage is the largest in these thermal storages.The experimental results of the GALISOL thermal storage with Ba(OH)2(8H2O indicates that in the heat-stored stage, the temperatures on the surface(3) of the encapsulation chamber of the phase-change material is uniform and the GALISOL thermal storage can keep high water temperature at the outlet for longer time. The heat-stored capacity unit volume and the heat-rejected strength of the GALISOL thermal storage is the largest in these thermal storages. (4) The experimental investigations for the heat-stored and heat-rejected PE solid particle packing bed show that it spends nearly 4 hours to reject well all the thermal storage in the packing bed. During experiments, the sublimation phenomena can be obviously observed. After experiments, a portion of the heat-stored material has been lost.(5) The numerically computed results for the heat-rejected behavior of PG solid particles packing bed show that in the heat-rejected stage, the air temperature at the outlet gradually decreases as the heat-rejected time increasing. At the same time, the air temperature at the outlet is higher for the smaller particle size (5mm) than for the larger one (6mm).