Experimental and Numerical Investigation of Integration of Cooled-ceiling, Nocturnal Sky Radiative Cooling and MPCM Slurry Thermal Storage

In recent years, new type phase change materials (PCM), microencapsulated phase change materials (MPCM) slurry, are investigated to be used as the thermal storage medium for building cooling applications to achieve the purpose of peak load shifting and energy saving. This study aims to investigate the thermal properties of MCPM slurry and develop proper MPCM slurry for air conditioning system combined with natural cooling source applications.;Firstly, latent heat of fusion, melting and solidification temperatures and supercooling degree of the material of PCM and MPCM slurry were investigated by using differential scanning calorimeter (DSC). An experimental test device with whole hybrid air conditioning system was also set up to measure the dynamic heat transfer performance of hybrid system combined with cooled ceiling system and MPCM slurry storage under the practical operation scheme. Supercooling and its effect on effective latent heat of MPCM slurry with different experimental conditions were also calculated and evaluated. Empirical equations were obtained to describe the relationship between the effective latent heat and the charging temperature.;Afterwards, carbon nanotube (CNT) was used as the nucleating agent for prevention of supercooling. Stable and homogenous dispersion of CNT in organic liquid was attained through surface modification plus the addition of surfactant. Thermal analysis of the n-hexadecane with well dispersed CNT particles indicated that the supercooling of n-hexadecane was significantly decreased with the concentration of 0.1% and 0.5% but only slightly with the concentrations over 1.0%. It appears that well dispersed nanoparticles provided stable foreign nuclei of proper size to promote the heterogeneous nucleation process and accelerate crystallization process.;At the end of the thesis, a mathematical model of the combined system of MPCM slurry, nocturnal sky radiator and cooled ceiling was built. The cooling energy consumption and the effect of energy-free nocturnal radiation application were simulated using the energy simulation code ACCURACY and MATLAB model based on hour-by-hour calculations. It can be drawn that MPCM slurry appears to be a good medium for the combined application of passive cooling technology and the nocturnal radiation in air conditioning system due to its relatively high working temperature.