In Vestigation Of Flow Melting Charteristics And Growth Process Of TBAB Clathrate Hydrate Slurry

The cool storage air conditioning is one of the main measures to move the electricityfrom the peak to the valley, which produces refrigeration power during off-peak periodand release the power in on-peak period to provide cooling for the building, and it hasbecome one the most important methods of overcoming the power crunch and cost saving.As a new kind of phase change material slurries (PCMS), Tetra-n-butyl-ammoniumbromide (TBAB) solution turns into clathrate hydrate slurry (CHS) when it is chilled inthe temperature range of0-12oC. Due to the high cold carry capacity and good flow andheat transfer performance, TBAB CHS is very promising to be used in air conditioning ordistrict cooling system for its energy-saving advantages.In this paper, the basic thermo-physical properties of TBAB CHS were introduced.On the basis of particular properties, the flow and heat transfer characteristics of TBABCHS in straight tube were investigated experimentally to let us have a further concept ofthe matter. The pressure drop and flow velocity of0~19.2wt%TBAB CHS was measured.It was found that TBAB CHS behaves as non-Newtonian fluid and can be described bypower-law model. The modified Reynolds number was recommended and theDodge-Metzner equation was determined as the suitable friction correlation for TBABCHS. The results showed that the constraint effect of tube wall on the flow of solidparticle in CHS had limited the flow, which resulted the amplification of friction factors.A heat transfer model was proposed based on the convection equation, momentumequation and continuity equation. The variation of the temperature along the tube was obtained.The inlet and outlet temperature, outer tube wall temperature and flow velocity of TBAB CHS inheated tube were measured. It was found that influence of heating flux on heat transfer was largerin smaller tube. The heat transfer coefficient increased with slurry fraction in laminar flow, whilethe heat transfer coefficient was influenced by flow velocity in turbulent flow. The empirical heattransfer correlation was proposed based on the experimental dates, and reports of ice slurry andmicroencapsulated phase change material (MPCM) slurry were used for reference.The crystallization and growth process of TBAB hydrate on copper surface has been investigated. The crystallization of the two types of TBAB hydrate were analyzed with thedigital photos and the temperature mutation due to the latent heat release during coolingprocess was interpreted. The growth velocity of the crystals is related to the texture of thecopper surface.