| On one hand,conventional Trombe wall has the advantages of the single construction,the low maintain cost and the low energy consumption.However,it also exists the disadvantages of the single function,the low energy utilization efficiency and the large heat loss at nighttime in winter.On the other hand,human beings have paid more and more focus on the indoor air pollution in recent years.Photocatalytic oxidation(PCO)purification technology and thermal catalytic oxidation(TCO)purification technology are two advanced active air purification technologies.Photocatalytic oxidation purification technology is a technology that the UV light drives the photocatalytical degradation of indoor pollutants over the common photocatalysts TiO2.And thermal catalytic oxidation purification technology is a technology that the thermal energy drives the thermal catalytical degradation of indoor pollutants over the thermal catalysts.Both the catalytic oxidation technologies have the huge potential on the combination application with solar energy.Therefore,this thesis combined the photocatalytic oxidation technology and the thermal catalytic oxidation technology with Trombe wall space heating technology and proposed a novel photocatalytic-thermal-catalytic-Trombe(PTC-Trombe)wall system.Based on the structures of conventional Trombe wall system,the photocatalytic glass and thermal catalytic layer replaces the glazing cover and the absorber plate,respectively.The combined system can realize dual functions of space heating and air purification,which realizes the solar gradient utilization.Under solar radiation,the UV light is absorbed by the photocatalytic layer of the photocatalytic glass,then the photocatalytic oxidation reaction is motivated.The rest visible light and infrared light parts are absorbed by the thermal catalytic layer.Then the temperature of the thermal catalytic layer increases and the thermal catalytic oxidation reaction is started when the thermal catalysts approach the light-off temperature.At the same time,the thermal catalytic layer heats the air in the air flow channel and conductes the heat to the massive wall,then the function of space heating is realized.This thesis conducted a series of studies on the PTC-Trombe wall system,which are as follows:1.This thesis conducted the feasibility analysis of Trombe wall hot air driven the thermal catalytic oxidation of formaldehyde over the thermal catalysts MnOx-CeO2.Firstly,transition metal oxides MnOx-CeO2 were selected as the experimental thermal catalysts and the kinetics of the thermal catalytic oxidation of indoor formaldehyde under different concentrations of 300?4300 ppb and thermal catalytic temperature levels of 20?100 ? were conducted.The experimental results showed that the selected thermal catalysts had excellent catalytic activity under the experimental conditions.The formaldehyde single-pass conversion ratio could approach 30%?60%when the catalytic temperature and formaldehyde concentration were 40?80 ? and 300 ppb,respectively.Then the experimental kinetic data were fitted and the fitting results showed that the thermal catalytic reaction rate considering two factors of formaldehyde concentration and thermal catalytic temperature fitted the modified bimolecular L-H model.Secondly,the experimental set-up of Trombe wall hot air driven the thermal catalytic oxidation of formaldehyde was built and the feasibility was investigated.The experimental results showed that this system could make the formaldehyde concentration all approach to Chinese IAQ standard(80 ppb)in 1 h under three typical indoor concentrations of 289 ppb,587 ppb and 1374 ppb.2.This thesis designed and fabricated thermal-catalytic-Trombe(TC-Trombe)wall system and built an experimental measuring set-up.Firstly,a full-day experiment was conducted to investigate the performances of air heating and formaldehyde degradation in TC-Trombe wall system.Secondly,the system thermal model was established and the system comprehensive performance was evaluated from the point of view of the thermal performance.Thirdly,the system energy saving potential was preliminarily evaluated in heating seasons in Hefei based on the established thermal model.Finally,this thesis proposed a novel comprehensive thermal catalytic mechanism to the formaldehyde degradation in TC-Trombe wall system.The experimental results showed that TC-Trombe wall had the excellent performances of air heating and formaldehyde degradation.Under the experimental total solar radiation energy of 7.89 MJ,the daily air heating efficiency,the total generated volume of the fresh air and the total degradation mass of formaldehyde were 41.3%,249.2 m3/(m2·day)and 208.4 mg/(m2 day),respectively.The energy saving calculation results showed that the total saving energy applied in Hefei could be up to 97.4 kWh/m2.Furthermore,this thesis proposed a novel hybrid tripartite catalytic mechanism integrated the photothermal conversion mechanism,the thermal catalytic oxidation mechanism and the solar photoactivation mechanism,which was responsible for the excellent catalytic activity for the formaldehyde degradation under solar radiation in TC-Trombe wall system.3.This thesis established a coupled thermal and mass transfer model of TC-Trombe wall verified by the experimental data.Using the climate data in heating seasons in Hefei,the effect of the thermal storage by the massive wall and the performance comparisons with conventional Trombe wall were investigated.Based on the analytical results,this thesis proposed a TC-Trombe wall with the sandwich structure.The results showed that due to the thermal storage by the massive wall,the total generated volume of the fresh air and the thermal load reduction by heating the air in the air flow channel in TC-Trombe wall system had the reductions of 24.9%and 15.8%,respectively.Compared with the conventional Trombe wall,the total thermal load reduction both from the air heating in the air flow channel and the thermal conduction by the massive wall had a reduction of 28.3%.However,TC-Trombe wall system could generate the total volume of the fresh air of 8328.7 m3/m2.TC-Trombe wall with the sandwich structure could effectively reduce the indoor thermal fluctuations.Compared with TC-Trombe wall system,the total generated volume of the fresh air and the total thermal load reduction in TC-Trombe wall system with the sandwich structure increased by 20.9%and 34.9%,respectively.The thermal performance in TC-Trombe wall system with the sandwich structure was comparable with that of in conventional Trombe wall system.4.The commercial photocatalysts TiO2(P25)were used as the experimental photocatalysts.This thesis designed and fabricated photocatalytic Trombe(PC-Trombe)wall system and built an experimental measuring set-up.Firstly,the experiments were conducted to investigate the performances of air heating and formaldehyde degradation.Secondly,this thesis established a coupled thermal and mass transfer model of PC-Trombe wall verified by the experimental data.Using the climate data in heating seasons in Hefei,the system energy saving potential was evaluated based on the established model.Under the experimental average solar radiation intensity of 631 W/m2 and average ambient temperature of 20.5 ?,the daily air heating efficiency,the total generated volume of the fresh air and the total degradation mass of formaldehyde were 35.1%,164.0 m3/(m2·day)and 100 mg/(m2 day),respectively.The energy saving calculatons showed that compared with the conventional Trombe wall system,the thermal load reduction from the air heating in the air flow channel and the total thermal load reduction from the thermal conduction by the massive wall in PC-Trombe wall system decreased by 23.9%and increased by 45.6%,respectively.This was because the adding of TiO2 layer decreased both the transmittance and the emissivity of the glazing cover.In the daytime,less solar radiation reached on the surface of the massive wall.While in the nighttime,less heat was lost into the ambient.Furthermore,PC-Trombe wall system could generate the total volume of the fresh air of 4764.9 m3/m2 in heating seasons.5.Based on the experimental and theoretical results of TC-Trombe wall and PC-Trombe wall,this thesis established a thermal and mass transfer model of PTC-Trombe wall system.Using the climate data in heating seasons in Hefei,the performances of space heating and formaldehyde degradation were evaluated based on the established model.Results showed that PTC-Trombe wall system could generate the total volume of the fresh air of 9482.2 m3/m2 in heating seasons,which was far greater than that of both in PC-Trombe wall and TC-Trombe wall.This is because PTC-Trombe wall system could fully use the solar radiation for the degradation of formaldehyde.UV was for photocatalytic degradation of formaldehyde and the rest of solar radiation was for solar thermal driven thermal catalytic degradation of formaldehyde.PTC-Trombe wall system could save the thermal load up to 296.1 MJ/m2,which was close to that of in PC-Trombe wall and far greater than that of in TC-Trombe wall.6.This thesis proposed a novel multifunctional photocatalytic-PV/T(PC-PV/T)system,which could realize the electricity generation,air purification,space heating and hot water supply.Based on the established thermal and mass transfer model,the effect of TiO2 coating density on the system performance including the thermal performance,electrical performance and formaldehyde degradation was investigated.In addition,the comparisons of PC-PV/T system with other two conventional PV/T systems were also been conducted.The results showed that the TiO2 coating density had an important effect on the system performance.The thermal performance and electrical performance decreased with the TiO2 coating density,while the performance of formaldehyde degradation increased with the TiO2 coating density.The electrical efficiencies of PC-PV/T system,PV/T air and water system,and PV/T air system were 0.125,0.144 and 0.143,respectively.However,the electrical efficiency of PC-PV/T system approached 0.174 when considering the saving electricity by degrading formaldehyde.The comprehensive thermal and electrical efficiencies of three PV/T systems were 0.644,0.696 and 0.677,respectively. |
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