Investigation Of Viscosity Charteristics And Flow Melting Charteristics In Mini-tubes Of Tbab Clathrate Hydrate Slurry

With the development of economy, the pressure from the imbalance between energy supply and energy demand become larger. The typical example is the large difference of electricity between peak and off-peak load. As we all know, air-conditioning consumes largest amount of electricity. The cold storage air conditioning has big advantage in energy-saving aspects. Tetra-n-butyl Ammonium Bromide clathrate hydrate slurry(TBAB CHS) has large energy storage densities and appropriate phase change temperature which can fit the temperature range of air conditioning system very well. And thus it is a promising cold storage material.In this paper, the forced flow and heat transfer characteristics of type A and type B TBAB CHS in mini-tubes with 2.0 mm and 4.5 mm in diameters were investigated.By analyzing the flow curves of TBAB CHS, both two types of TBAB CHS shows shear-thinning characteristics. Power-law model was applied to describe the flow behavior of TBAB CHS. The results of flow behavior index and fluid consistency coefficient show that both the solid fraction of TBAB CHS and tube diameter would have great influence on the fluidity of TBAB CHS. Considering TBAB CHS belongs to solid-liquid two phases fluid, the modified Reynold number was applied. On base of the modified Reynold number, Dodge-Metzner equation was selected to predict friction factors and the calculated results were compared with experimental data. Due to different crystal sizes and morphologies, the pressure drop type A TBAB CHS was larger than that of type B, which indicated that type B TBAB CHS is more appropriate for application.The local heat transfer coefficient of type A and type B TBAB CHS increases with flow velocity and inlet mass fraction. Heating power and mass fraction of TBAB CHS were the most important influential factors in laminar flow region while flow velocity was the most important influential factor in turbulent flow region. The results show that the homogeneous model, which was used to simulate the flow melting situation, can depict that behavior of TBAB in mini-tube more reasonably. When the thermal conditions were similar, the local heat transfer coefficient of type A was smaller than that of type B. For both type A and type B TBAB CHS, the heat transfer correlations were developed and the maximum deviation between experimental data and developed correlations is ±20%.The rheological properties of TBAB CHS are investigated using Brookfield R/S Rheomerter. Shear stress and shear rate of TBAB solution and TBAB CHS were measured with the mass fraction in the range of 0-25.0%. Power-law equation was used to describe the flow behavior of both two types of TBAB CHS. The results show that TBAB solution appeared as Newtonian fluid when the shear rate below 1000 s-1. And TBAB CHS shows shear-thinning characteristics. The flow behavior index and fluid consistency show good consistency with the results in previous results in 2.0 mm mini-tube.