This paper analyzes the convective heat transfer enhancement mechanism of latent heat functionally thermal fluid. By using the proposed internal heat source model, the influence of each factor affecting the heat trans...This paper analyzes the convective heat transfer enhancement mechanism of latent heat functionally thermal fluid. By using the proposed internal heat source model, the influence of each factor affecting the heat transfer enhancement of laminar flow in a circular tube with constant heat flux is analyzed. The main influencing factors and the mechanisms of heat transfer enhancement are clarified, and the influences of the main factors on the heat transfer enhancement are quantitatively analyzed. A modified Nusselt number for internal flow is introduced to describe more effectively the degree of heat transfer enhancement for latent functionally thermal fluid.展开更多
The latent heat of the microencapsulated phase change material(MPCM)increases the effective ther-mal capacity of latent functionally thermal fluid.However,researchers found that the heat transfer performance of such f...The latent heat of the microencapsulated phase change material(MPCM)increases the effective ther-mal capacity of latent functionally thermal fluid.However,researchers found that the heat transfer performance of such fluids was diminished due to the reduction of the low thermal conductivity of MPCM.For this reason,the nanoparticle enhanced latent functionally thermal fluids were formulated and the heat transfer behaviors of these fluids in a vertical circular tube at the laminar regime were conducted.The result showed that slurries containing 0.5% TiO2 nanoparticles by mass and 5%―20% MPCM by mass exhibited improved heat transfer rates in comparison with the conventional latent functionally thermal fluid and that the enhancement increased with the increasing MPCM concentration and up to 18.9% of the dimensionless wall temperature was reduced.展开更多
The heat transfer of latent functionally thermal fluid in three kinds of tubes with coaxially inserted cylindrical bars is numerically researched using equivalent spe- cific heat model, and the flow fields are analyze...The heat transfer of latent functionally thermal fluid in three kinds of tubes with coaxially inserted cylindrical bars is numerically researched using equivalent spe- cific heat model, and the flow fields are analyzed with field synergy field. It is found that in the tubes with coaxially inserted cylindrical bars, the heat transfer effects of functionally thermal fluid become more and more pronounced with the Ste de- creasing. This is similar to be case of functionally thermal fluid flowing in smooth straight tubes. Compared with the results receiving from smooth straight tubes, the heat transfer of functional thermal fluid in tubes with coaxially inserted cylindrical bars has been significantly enhanced. And this effect becomes more apparent as the diameter of coaxially inserted cylindrical bars increases meanwhile, however, energy consuming of the tubes shows the same trend.展开更多
In this paper, a new model to analyze laminar forced convective enhanced heat transfer in latent function-ally thermal fluid is developed. The main characteristics of the model are: i) a new formula of the specific he...In this paper, a new model to analyze laminar forced convective enhanced heat transfer in latent function-ally thermal fluid is developed. The main characteristics of the model are: i) a new formula of the specific heat at con-stant pressure is used; ⅱ) a real heat transfer process is considered; that is, heat transfer processes occur not only between working fluid and microcapsules, but also between the mixture and tube wall; ⅲ) the new method, which com-bines the newly developed axisymmetrical dual reciprocity boundary element method (DRBEM) with finite difference method (FDM), is used to solve the control equations of this problem. The new model is validated by experimental data. Some new physical results on the variational characteristics of the specific heat at constant pressure with space and time during phase-change process, the time-marching history of the phase-change interfaces and so on are obtained. Several main physical factors that affect enhanced heat transfer in latent functionally thermal fluid are numerically analyzed. Some new understandings for the mechanism of enhanced heat transfer in the functionally fluid are obtained.展开更多
Latent functionally thermal fluids (LFTF) are a novel kind of heat storage and heat transfer fluids that in- clude phase change microcapsule slurry and phase change emulsion (PCE). They have much greater apparent spec...Latent functionally thermal fluids (LFTF) are a novel kind of heat storage and heat transfer fluids that in- clude phase change microcapsule slurry and phase change emulsion (PCE). They have much greater apparent specific heats and higher heat transfer abilities in the phase change temperature range than conventional single-phase heat transfer fluids such as water. Thus they are advantageous in the field of the convective heat transfer enhancement and energy transport. In this paper, some thermal physical prop- erties such as viscosity, fusion heat and apparent specific heat (cp) are measured, and the influences of some factors (such as selection of surfactants, preparation method, temperature, mixing ratio of surfactants and mass concentration of phase change material) on them are discussed. The study shows that: 1) the viscosity of the PCE prepared in the present work is lower than that reported in the literature; 2) its ap- parent specific heat value for the phase change temperature region is high and proportionally increases with the concentration of phase change material.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.50076020)the Key Projects of Basic Research and Development of China(Grant No.G2000026309)the Excellent Young Faculty Foundation of the Ministry of Education of China.
文摘This paper analyzes the convective heat transfer enhancement mechanism of latent heat functionally thermal fluid. By using the proposed internal heat source model, the influence of each factor affecting the heat transfer enhancement of laminar flow in a circular tube with constant heat flux is analyzed. The main influencing factors and the mechanisms of heat transfer enhancement are clarified, and the influences of the main factors on the heat transfer enhancement are quantitatively analyzed. A modified Nusselt number for internal flow is introduced to describe more effectively the degree of heat transfer enhancement for latent functionally thermal fluid.
基金Supported by the National Natural Science Foundation of China(Grant No. 50076020)
文摘The latent heat of the microencapsulated phase change material(MPCM)increases the effective ther-mal capacity of latent functionally thermal fluid.However,researchers found that the heat transfer performance of such fluids was diminished due to the reduction of the low thermal conductivity of MPCM.For this reason,the nanoparticle enhanced latent functionally thermal fluids were formulated and the heat transfer behaviors of these fluids in a vertical circular tube at the laminar regime were conducted.The result showed that slurries containing 0.5% TiO2 nanoparticles by mass and 5%―20% MPCM by mass exhibited improved heat transfer rates in comparison with the conventional latent functionally thermal fluid and that the enhancement increased with the increasing MPCM concentration and up to 18.9% of the dimensionless wall temperature was reduced.
基金Supported by the Key Project of National Natural Science Foundation of China (Grant No. 50436020)
文摘The heat transfer of latent functionally thermal fluid in three kinds of tubes with coaxially inserted cylindrical bars is numerically researched using equivalent spe- cific heat model, and the flow fields are analyzed with field synergy field. It is found that in the tubes with coaxially inserted cylindrical bars, the heat transfer effects of functionally thermal fluid become more and more pronounced with the Ste de- creasing. This is similar to be case of functionally thermal fluid flowing in smooth straight tubes. Compared with the results receiving from smooth straight tubes, the heat transfer of functional thermal fluid in tubes with coaxially inserted cylindrical bars has been significantly enhanced. And this effect becomes more apparent as the diameter of coaxially inserted cylindrical bars increases meanwhile, however, energy consuming of the tubes shows the same trend.
文摘In this paper, a new model to analyze laminar forced convective enhanced heat transfer in latent function-ally thermal fluid is developed. The main characteristics of the model are: i) a new formula of the specific heat at con-stant pressure is used; ⅱ) a real heat transfer process is considered; that is, heat transfer processes occur not only between working fluid and microcapsules, but also between the mixture and tube wall; ⅲ) the new method, which com-bines the newly developed axisymmetrical dual reciprocity boundary element method (DRBEM) with finite difference method (FDM), is used to solve the control equations of this problem. The new model is validated by experimental data. Some new physical results on the variational characteristics of the specific heat at constant pressure with space and time during phase-change process, the time-marching history of the phase-change interfaces and so on are obtained. Several main physical factors that affect enhanced heat transfer in latent functionally thermal fluid are numerically analyzed. Some new understandings for the mechanism of enhanced heat transfer in the functionally fluid are obtained.
基金the National Natural Science Foundation of China(Grants No.50076020, 50436020)the National Key Basic Research Special Fund Project(Grant No.G2000026309).
文摘Latent functionally thermal fluids (LFTF) are a novel kind of heat storage and heat transfer fluids that in- clude phase change microcapsule slurry and phase change emulsion (PCE). They have much greater apparent specific heats and higher heat transfer abilities in the phase change temperature range than conventional single-phase heat transfer fluids such as water. Thus they are advantageous in the field of the convective heat transfer enhancement and energy transport. In this paper, some thermal physical prop- erties such as viscosity, fusion heat and apparent specific heat (cp) are measured, and the influences of some factors (such as selection of surfactants, preparation method, temperature, mixing ratio of surfactants and mass concentration of phase change material) on them are discussed. The study shows that: 1) the viscosity of the PCE prepared in the present work is lower than that reported in the literature; 2) its ap- parent specific heat value for the phase change temperature region is high and proportionally increases with the concentration of phase change material.
