To offer a potentially low-cost and high-efficiency option for once-through applications,the unglazed transpired solar collector was studied. The semi-empirical correlation of overall heat exchange effectivenessε for...To offer a potentially low-cost and high-efficiency option for once-through applications,the unglazed transpired solar collector was studied. The semi-empirical correlation of overall heat exchange effectivenessε for UTC with circular holes was proposed to verify whether it being fit for this kind of absorber with slit-like perforations. The results show that in certain parameters,the predicted values of ε are very close to measured values,and the root mean square difference in betweens about 0.10,so the modle is suitable. Based on experimental results,this kind of absorber is proved to be feasible,with highest value of ε,up to 0.81. In addition,with the increase of γ,overall heat exchange effectiveness ε will decrease,i.e.,the value of ε will decrease with the increase of suction velocity vs or the decrease of wind velocity uw. However,the actual value of solar radiation intensity G and ambient temperature T∞ have little influence on ε.展开更多
A density functional theory is applied to calculating the local density profiles of colloids confined in a slit-like pore as well as the radial distribution functions of bulk colloids. The interaction between the coll...A density functional theory is applied to calculating the local density profiles of colloids confined in a slit-like pore as well as the radial distribution functions of bulk colloids. The interaction between the colloidal particles is described using a hard-core Yukawa model. The excess Helmholtz energy functional is a combination of the modified fundamental measure theory of Yu and Wu （2002） for the hard-core contribution and a corrected mean-field theory for the attractive contribution. Comparison with the results from the Monte Carlo simulations shows that the corrected theory improves the density profiles of colloids in the vicinity of contact over the original mean-field theory. Both the present corrected theory and simulations suggest that there are depletion and desorption for the colloid with strong attraction between particles at low temperature.展开更多
基金Project (2006BAJ04B01-3) supported by the National Science and Technology Pillar Program during the 11th Five-year Plan Period of Chinaproject(09JCZDJC24600) supported by Natural Science Foundation of Tianjin City of China
文摘To offer a potentially low-cost and high-efficiency option for once-through applications,the unglazed transpired solar collector was studied. The semi-empirical correlation of overall heat exchange effectivenessε for UTC with circular holes was proposed to verify whether it being fit for this kind of absorber with slit-like perforations. The results show that in certain parameters,the predicted values of ε are very close to measured values,and the root mean square difference in betweens about 0.10,so the modle is suitable. Based on experimental results,this kind of absorber is proved to be feasible,with highest value of ε,up to 0.81. In addition,with the increase of γ,overall heat exchange effectiveness ε will decrease,i.e.,the value of ε will decrease with the increase of suction velocity vs or the decrease of wind velocity uw. However,the actual value of solar radiation intensity G and ambient temperature T∞ have little influence on ε.
基金This work is sponsored by the National Natural Science Foun’ dation of China(Grant No．20376037) the National Basic Research Pr0gram of China(Grant No．2003CB61 5700)
文摘A density functional theory is applied to calculating the local density profiles of colloids confined in a slit-like pore as well as the radial distribution functions of bulk colloids. The interaction between the colloidal particles is described using a hard-core Yukawa model. The excess Helmholtz energy functional is a combination of the modified fundamental measure theory of Yu and Wu （2002） for the hard-core contribution and a corrected mean-field theory for the attractive contribution. Comparison with the results from the Monte Carlo simulations shows that the corrected theory improves the density profiles of colloids in the vicinity of contact over the original mean-field theory. Both the present corrected theory and simulations suggest that there are depletion and desorption for the colloid with strong attraction between particles at low temperature.
