Experimental Study On Promoting Hydrate Formation With Solid Surface

With the development of economy,the demand for electricity is increased gradually.The ratio of building energy consumption to total energy consumption has increased when air-conditioning is used more and more widely.The load of power grid becomes unbalanced due to unsynchronized use of air-conditioning.Cold storage air-conditioning can make full use of off-peak power to reduce the peak demand.As a kind of cold storage medium,hydrate has been studied widely,mainly due to its advantages such as suitable cold storage temperature and large cold storage density.However,it also has some shortcomings such as long induction time of hydrate formation and low production quantity.How to overcome these shortcomings has become the key research field of hydrate cold storage.Based on the nucleation mechanism of hydrate,solid materials were added into the hydrate system to study the effect of solid surface on hydrate formation,which is mainly divided into the following contents:(1)The effects of solid type,surface area and shape on tetrahydrofuran(THF)hydrate formation were investigated.The experimental results show that copper mesh has the best promoting effect on hydrate formation.The induction time of hydrate formation decreases with the increase of solid surface area.(2)Copper mesh and surfactant SDS were added separately or simultaneously to study the formation of hydrate.The results show that 40 mesh copper mesh has better effect on THF hydrate formation than that of 80 mesh copper mesh.The induction time of THF hydrate formation decreases with the number of copper mesh layers increases and the reduction of experimental temperature.Compared with the cylindrical copper mesh,the induction time of THF hydrate formation is relatively stable in the presence of W-shape copper mesh.There is no significant promoting effect on HCFC-141 b hydrate by adding40 mesh rectangular copper mesh.Adding SDS separately has no promoting effect on hydrate.The induction time of THF hydrate formation is the shortest,about 84 min when400ppm SDS and 40 mesh cylindrical copper mesh were added simultaneously,and the induction time of HCFC-141 b hydrate is the shortest with 800 ppm SDS and 40 mesh rectangular copper mesh.The average temperature rise of HCFC-141 b hydrate formation is the highest when 1000 ppm SDS and 40 mesh rectangular copper mesh were added simultaneously.(3)Carboxylated multi-walled carbon nanotubes(MWCNT-COOH)were dispersed indistilled water to study their effect on the formation of HCFC-141 b hydrate.The experimental results show that MWCNT added separately or in combination with1000 ppm SDS has no significant promoting effect.MWCNT at a mass concentration of40 ppm has the best promoting effect on hydrate when MWCNT nanofluid and 40 mesh rectangular copper mesh were added simultaneously.The randomness of hydrate formation is reduced when MWCNT nanoemulsion and 40 mesh rectangular copper mesh were added simultaneously,and 40 ppm MWCNT is the best addition.(4)The cold storage densities of HCFC-141 b hydrate in the systems of copper mesh+SDS,copper mesh+nanofluid and copper mesh+nanomulsion were measured by the mixing calorimetry,which are 157.2kJ/kg,180.6kJ/kg and 110.8kJ/kg,respectively.