Cement-free castables have attracted significant attention due to their superior thermal-mechanical properties and rapid dry-out in comparison to cement-bonded refractory castables.However,drying industrial-scale spec...Cement-free castables have attracted significant attention due to their superior thermal-mechanical properties and rapid dry-out in comparison to cement-bonded refractory castables.However,drying industrial-scale specimens can pose more challenges than lab-scale samples.In this study,the dry-out behavior and explosion resistance of microsilica-gel bonded nocement castables(NCCs)were investigated on both lab-and industrial-scale specimens,employing various drying agents.First,the fast dry-out mechanism was assessed using thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),and scanning electron microscopy(SEM)on lab-scale small samples.Then,the drying behavior of industrial-scale large samples(300 mm×300 mm×300 mm cubes,approximately 80 kg)was studied using a unique macro-thermo-balance(macro-TGA).The results showed that EMSIL-DRY^(®)reduced the temperature level for maximum dewatering rate and effectively prevented explosions during heat-up,compared to other polymer fibres.The use of a specialty drying agent(EMSIL-DRY^(®))significantly improved the explosion resistance,as demonstrated by the production of a perfect 400 kg block fired to 850℃at a rate of 50℃·h^(-1).This research contributes to the understanding and application of cement-free castables in industrial settings.展开更多
Microchannel flow boiling heat transfer has the advantages of strong heat dissipation capacity,good temperature uniformity,and compact structure.It is an excellent way to thermally manage electronic devices,but when t...Microchannel flow boiling heat transfer has the advantages of strong heat dissipation capacity,good temperature uniformity,and compact structure.It is an excellent way to thermally manage electronic devices,but when the heat flux exceeds CHF(Critical Heat Flux),the heat transfer performance deteriorates as the working fluid dries out.Non-azeotropic mixtures have the potential to effectively delay or avoid dry-out during the boiling process due to their temperature slide characteristics which causes the mass transfer resistance.To understand the influence of non-azeotropic mixtures on microchannel flow boiling,using the phase-change microchannel heat sink as the research object,the experiments on the flow boiling heat transfer performance of R245fa/R134a mixtures under different working conditions were carried out,and the characteristics of flow boiling heat transfer were obtained under the different working conditions,and comparison was developed with those of pure substance R245fa.The results demonstrated that a small amount of low-boiling-point components in the high-boiling-point working fluid inhibited boiling heat transfer to some extent,and lowered the average heat transfer coefficient under the non-dryout condition slightly lower than that of the pure substance;however,it also effectively delayed the onset of local dry-out and prevented significant deterioration in thermal transfer performance under the lower mass flow rate and higher heat flux,which could enhance the heat sink's stability.展开更多
文摘Cement-free castables have attracted significant attention due to their superior thermal-mechanical properties and rapid dry-out in comparison to cement-bonded refractory castables.However,drying industrial-scale specimens can pose more challenges than lab-scale samples.In this study,the dry-out behavior and explosion resistance of microsilica-gel bonded nocement castables(NCCs)were investigated on both lab-and industrial-scale specimens,employing various drying agents.First,the fast dry-out mechanism was assessed using thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),and scanning electron microscopy(SEM)on lab-scale small samples.Then,the drying behavior of industrial-scale large samples(300 mm×300 mm×300 mm cubes,approximately 80 kg)was studied using a unique macro-thermo-balance(macro-TGA).The results showed that EMSIL-DRY^(®)reduced the temperature level for maximum dewatering rate and effectively prevented explosions during heat-up,compared to other polymer fibres.The use of a specialty drying agent(EMSIL-DRY^(®))significantly improved the explosion resistance,as demonstrated by the production of a perfect 400 kg block fired to 850℃at a rate of 50℃·h^(-1).This research contributes to the understanding and application of cement-free castables in industrial settings.
基金supported by the National Natural Science Foundation of China(No.52076185)the Natural Science Foundation of Zhejiang Province(No.LZ19E060001)the Open Project of Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering(No.KF2019-02)。
文摘Microchannel flow boiling heat transfer has the advantages of strong heat dissipation capacity,good temperature uniformity,and compact structure.It is an excellent way to thermally manage electronic devices,but when the heat flux exceeds CHF(Critical Heat Flux),the heat transfer performance deteriorates as the working fluid dries out.Non-azeotropic mixtures have the potential to effectively delay or avoid dry-out during the boiling process due to their temperature slide characteristics which causes the mass transfer resistance.To understand the influence of non-azeotropic mixtures on microchannel flow boiling,using the phase-change microchannel heat sink as the research object,the experiments on the flow boiling heat transfer performance of R245fa/R134a mixtures under different working conditions were carried out,and the characteristics of flow boiling heat transfer were obtained under the different working conditions,and comparison was developed with those of pure substance R245fa.The results demonstrated that a small amount of low-boiling-point components in the high-boiling-point working fluid inhibited boiling heat transfer to some extent,and lowered the average heat transfer coefficient under the non-dryout condition slightly lower than that of the pure substance;however,it also effectively delayed the onset of local dry-out and prevented significant deterioration in thermal transfer performance under the lower mass flow rate and higher heat flux,which could enhance the heat sink's stability.
