Application Of Photocatalytic Degradation In The Heating Mode Of Trombe Wall

Recently,more and more attention has been paid to indoor environment and building energy saving.With the increasing populality of interior decoration,the problem of indoor air pollution has become seriously.Formaldehyde is one of the representative indoor air pollutants.This article combines indoor formaldehyde degradation with building heating.Photocatalytic degradation technology is applied to the heating mode of the Trombe wall,and the performance of the photocatalytic Trombe wall is studied.In this paper,the photocatalyst Degussa P25 was sprayed on the borosilicate glass cover plate by spray coating under laboratory conditions.Sodium metasilicate nonahydrate(Na2SiO3·9H2O)was used as a binder and a large number of spraying experiments were carried out to explore the optimal mass ratio of binder and photocatalyst.The results showed that when the mass ratio of binder and photocatalyst was 1:40,the formaldehyde degradation rate of the film was highest and the film was uniform.2.2 g of photocatalyst was loaded on two glass cover plates(0.5 m × 0.5 m × 0.003 m)and the average film thickness was 44 ?m.The visible and ultraviolet transmittance of the glass cover plate coated with the photocatalyst was tested,and the value was 77.8%and 5%,respectively.An experimental test platform for photocatalytic and traditional Trombe wall was built in Hefei,and comparative experiments were conducted to explore the formaldehyde degradation and heating performance of the photocatalytic Trombe wall.The results showed that photocatalytic Trombe wall could degrade formaldhyde while traditional Trombe wall had no formaldhyde degradation function.When formaldehyde inlet concentration was from 0.7 to 1.2 ppm,the photocatalytic Trombe wall(solar irradiation accepting area of 0.5 m2)had a single-pass degradation rate ranging from 0.2 to 0.4 and a degradation rate ranging from 0.006 to 0.019 ppb·m·s-1.The amount of hourly generated clean air and total generated air could reach 5?10 m3/h and 56 m3 respectively.The thermal performance of photocatalytic Trombe wall was lower than that of traditional Trombe wall.The total heat gain and daily average thermal efficiency of photocatalytic Trombe wall reached 1.14 kW·h and 0.27 respectively.By fitting the instantaneous thermal efficiency of the two systems through polynomials,it was found that the time of the maximum instantaneous thermal efficiency of photocatalytic Trombe wall was delayed compared to the traditional Trombe wall.A theoretical simulation study of the photocatalytic Trombe wall was carriedout.The Trombe wall heat transfer equation and the indoor formaldehyde transfer equation were established,and the influence of different parameters on the performance of the system was studied.The results showed that with higher solar irradiation,higher ambient temperature and lower inlet temperature,the instantaneous thermal efficiency of the photocatalytic Trombe wall was higher.Under the condition of lower inlet formaldehyde concentration,smaller ventilation coefficient,smaller room area to be treated and greater CADR,the equilibrium formaldehyde concentration of the treated room was lower and the required equilibrium time was shorter.Compared with air purifiers and air conditioners,using photocatalytic Trombe wall(per square meter)for heating and indoor air purification could save electricity of 19.3 kW·h per month or standard coal of 2.4 kg per month.