| Facing the current situation of energy shortage,phase changing thermal storage materials can solve the contradiction of heat supply in space and time.This experiment conducted studies on low-temperature phase changing thermal storage material made up by crystalline hydrated salt,through preparing CaCl2·642O and Na2SO4·10H2O,and cold experiment for the analytical purity and industrial purity(blank group)samples.The improved group mixed appropriate coolant and thickening agent(according to the quality of the relative material),and repeated the fusion freezing experiment for 5 to 25 times to determine the cold degree,and select the suitable cold agent.Finally,the experiment conducted the heat performance test to testify the phase change latent heat and phase transition temperature of the required heat storage system,and conducted simulation to testify the heat storage effect.The experiment showed the followings:(1)For CaCl2·6H2O thermal storage system,the supercooling degree of analytical purity and industrial purity CaCl2·6H2O were 21.2? and 16.0?.Selected the dose of 1%CMC as thickener to phase separation;choose BaF2,BaCO3,Na2B4O7·10H2O,SrCl2·6H2O as refrigerant;melt-frozen temperature range was from-8? to 40?.The BaF2 has poor capability to maintain systematic temperature;BaCO3,Na2B4O7·10H2O,SrCl2·6H2O reduced supercooling degree to 9.4?,4.6?,3.3?,the blank groups respectively reduced by 41.3%,71.3%and 79.4%and determined optimum adding amount of Na2B4O7·10H2O was 2.3%,and the latent heat of the corresponding CaCl2·6H2O/Na2B4O7·10H2O was 127.6J/g;system transformation temperature was 28.5?;the melting peak temperature was 33.2?;after 25 times of circulation the latent heat was 124.3J/g;transformation temperature was 28.3?,the melting peak temperature was constant,the heat loss was 2.59%.Between 18? and 40? the average heat capacity was 2.74J/g·K.The experiment found SrCl2·6H2O optimum adding amount was 3.1%and 3.2%(3.1%);the corresponding CaCl2·6H2O/SrCl2·6H2O latent heat was 129.3J/g;system transformation temperature was 29.1 ?,the melting peak temperature was 33.5?.After circulation for 25 times of latent heat was 128.1J/g;transformation temperature was 28.9?;the melting peak temperature was constant,heat loss 0.93%;between 18? and 40? the average heat capacity was 2.81J/g·K.(2)For Na2SO4·10H2O thermal storage system,the supercooling degree of the analytical purity and industrial purity Na2SO4·10H2O was respective 12.8? and 13.7?.Selected the dose of 1%CMC as thickener to resist phase separation;selected of MgCl2·6H2O,Na2B4O7·10H2O,NH4B5O8·4H2O as refrigerant,and melt-frozen temperature range was from-12? to 40?.The MgCl2·6H2O,Na2B4O7·10H2O,NH4B5O8·4H2O reduced the supercooling degree to 9.4?,6.4?,7.6?,which decreased by 31.4%,53.3%and 44.5%respectively compared with the blank group.Figured out that the optimal amount of MgCl2·6H2O,Na2B4O7·10H2O,NH4B5O8·4H2O to add was 2.4%,3.3%and 2.2%-2.4%.The latent heat of the Na2SO4·10H2O/Na2B4O7·10H2O system was 167.7J/g;the phase change point was 32.1?;the melting peak temperature was 38.2?,and the latent heat of after circulation for 25 times was 163.2J/g;the phase change point was 32?;the melting peak temperature was 38.3?,and the heat loss was 2.68%;the average specific heat capacity in 18?-40? was 2.44J/g·K. |
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