Thermal Transfer Model Research Articles

Interfacial separation in CRTS Ⅱ type slab track structure subjected to continuous high temperatures: Thermal and moisture effects

To investigate the formation mechanism of cracking in track slab-CA mortar layers under continuous high-temperature conditions, a thermal and moisture coupling deformation theory was used to analyze interlayer damage in ballastless track structures. Firstly, the thermal and moisture coupling deformation and interlayer damage model of the CRTS Ⅱ type slab track structure was established by integrating the thermal and moisture coupling transfer model with the cohesive force damage model through the use of equivalent temperature differentials. The accuracy of the model was verified by setting up an indoor test bench. Secondly, based on the coupled heat and humidity transfer model of the slab-type ballastless track, the distribution characteristics of the temperature and capillary pressure fields were calculated and analyzed using COMSOL Multiphysics® software and the summer meteorological data in Hangzhou, China. The results indicate that the influence depth of drying rapidly developed to 20 mm on day 1, and expanded to 60 mm on day 6; the expansion rate gradually slowed until it reached 120 mm on the 25th day and finally 150 mm on the 40th day. Finally, based on this, the finite element software ABAQUS was used to comparatively analyze the thermal deformation and coupling deformation of both thermal and moisture effects, as well as interlayer damage in the CRTS Ⅱ type slab track structure in the unit state and longitudinal connection state. The results indicate that drying shrinkage can hinder upward arch displacement and damage to the track slab based on the temperature gradient, while significantly worsening upward warping displacement and damage to the track slab. The upward arch displacement decreased by 21.24 % in the unit state and 22.67 % in the longitudinally connected state on the 40th day, while the upward warping displacement increased by 62.17 % and 32.22 %, respectively. Therefore, it is crucial to investigate how moisture deformation impacts the cracking of the track slab-CA mortar layer, as a significant research factor.

Model Optimization of Ice Melting of Bridge Pylon Crossbeams with Built-In Carbon Fiber Electric Heating

This paper aims to improve the deicing performance and energy utilization of bridge pylon crossbeams with built-in carbon fiber electric heating (BPB–CFEH). Therefore, a three-dimensional thermal transfer model of BPB–CFEH with one arrangement is established. Two ice-melting regions and two ice-melting stages were set up according to the characteristics of the icing of the crossbeam. The effects of wind speed and ambient temperature on the paving power required to reach the complete melting of the icicles within 8 h were analyzed. The effects of the laying spacing and rated voltage of the carbon fiber heating cable on the melting ice sheet and the thermal exchange of the two regions of the icicle after heating for 8 h were compared. Additionally, its effect on energy utilization of the process from the ice sheet melting stage to the ice column melting stage was analyzed. Ice-melting experiments verified the applicability and reasonableness of the simulated ice-melting calculation formula. The results show that under ambient temperature of −10 °C and wind speed of 4.5–13.5 m/s, the proposed paving power is 817.5–2248.12 W/m2. Increasing the rated voltage and shortening the spacing increases the thermal exchange capacity of the two melting regions. The shortening of the spacing improves the energy utilization rate of the melting stage of the ice sheet to the melting stage of the icicle processes. The difference between the melting time obtained from the formula proposed by numerical simulation and the melting time obtained from indoor tests is about 10 min. This study provides a design basis for the electrothermal ice melting of bridge pylon crossbeams.

A reduced-order model for nonlinear radiative transfer problems based on moment equations and POD-Petrov-Galerkin projection of the normalized Boltzmann transport equation

A data-driven projection-based reduced-order model (ROM) for nonlinear thermal radiative transfer (TRT) problems is presented. The TRT ROM is formulated by (i) a hierarchy of low-order quasidiffusion (aka variable Eddington factor) equations for moments of the radiation intensity and (ii) the normalized Boltzmann transport equation (BTE). The multilevel system of moment equations is derived by projection of the BTE onto a sequence of subspaces which represent elements of the phase space of the problem. Exact closure for the moment equations is provided by the Eddington tensor. A Petrov-Galerkin (PG) projection of the normalized BTE is formulated using a proper orthogonal decomposition (POD) basis representing the normalized radiation intensity over the whole phase space and time. The Eddington tensor linearly depends on the solution of the normalized BTE. By linear superposition of the POD basis functions, a low-rank expansion of the Eddington tensor is constructed with coefficients defined by the PG projected normalized BTE. The material energy balance (MEB) equation is coupled with the effective gray low-order equations which exist on the same dimensional scale as the MEB equation. The resulting TRT ROM is structure and asymptotic preserving. A detailed analysis of the ROM is performed on the classical Fleck-Cummings (F-C) TRT multigroup test problem in 2D geometry. Numerical results are presented to demonstrate the ROM's effectiveness in the simulation of radiation wave phenomena. The ROM is shown to produce solutions with sufficiently high accuracy while using low-rank approximation of the normalized BTE solution. Essential physical characteristics of supersonic radiation wave are preserved in the ROM solutions.

Optimization of MTI structure based on material characteristics under extreme aerodynamic heating environment

Thermal insulation structure is a key factor to protect a high-speed aircraft to work safely and complete various tasks. The multilayer thermal insulation (MTI) structure has attracted much attention because of its light weight and good thermal insulation effect. The performance of an MTI structure is not only related to its physical sizes, but also closely related to the material optimization and temperature influences. A transient nonlinear thermal transfer model of the MTI structure is established, and a numerical solution strategy of the nonlinear thermal transfer model is proposed. Considering material selection, introducing the temperature influence of materials, and taking the geometric dimensions and equivalent mechanical properties of the MTI structures as constraints, an optimization frame of the MTI structures is established. Then two intelligent methods are adopted to solve the problem. Using the aerodynamic heating environment of X-43 flight trajectory, the results of a typical high-speed aircraft show that the proposed optimization framework can reduce the structural mass density from 13.95 kg‧m−2 to 9.10 kg‧m−2 by about 34.8 %. The temperature effect analysis shows that the temperature variation has an important influence on the optimization results. If the temperature effect on material properties is not considered, the optimized design scheme may not meet the temperature design constraints (The maximum temperature of the inner surface is 410 K, far exceeding the maximum allowable temperature of 320 K) which further leads to structural failures. Finally, the reliability and rationality of the optimization scheme are verified by a finite element model (FEM). The equivalent modulus of the optimized MTI structure is 146 GPa and the mass area density of the MTI structure is 7.7 kg‧m−2. The optimization design method of an MTI structure proposed in the current paper provides a technical support and lays a foundation for the overall design of a high-speed aircraft.

Improving Critical Frequency of the Electrothermal V-Shaped Actuator Using the Particle Swarm Optimization Algorithm

This paper presents a thermal transfer model and optimization of a V-beam dimension to improve the critical frequency fC (i.e., expanding the effective working frequency range) of an electrothermal V-shaped actuator (EVA). The obtained results are based on applying the finite difference model, a method for calculating the critical frequency, as well as conditions to ensure the mechanical stability and thermal safety of EVA. The influence of beam dimensions (i.e., length L, width w , and incline angle θ of the beam) on the variation of critical frequency fC is investigated and evaluated. Moreover, the particle swarm optimization (PSO) algorithm is used to figure out the optimal beam dimensions aiming to increase the critical frequency while satisfying conditions such as mechanical stability, thermal safety, and suitable displacement of EVA. With the optimal dimensions of V-beam (L = 679 µm, w = 4 µm, and θ = 1.8°), the critical frequency of the V-shaped actuator can be achieved up to 136.22 Hz at a voltage of 32 V (average increment of fC is 33.1% with the driving voltage changing from 16 V to 32 V) in comparison with the nonoptimal structure (fC is only 102.34 Hz at 32 V).

Microwaving Mimas, Enceladus, Tethys, Dione, Rhea, Iapetus and Phoebe: Insights into the regolith properties and geological history of Saturn's icy satellites

While Saturn's main airless moons are all composed largely of water ice, their respective thermal histories and near environments have led to different regolith compositions and structures. Part of this history is recorded in their subsurface which can be probed by microwaves. Using a combined thermal and radiative transfer model, we here investigate all distant observations acquired in the passive mode of the RADAR on board the Cassini spacecraft (2004–2017) at 2.2-cm wavelength. The joint analysis of the derived disk-integrated emissivities and published radar albedos provides new insights into the purity and maturity of the regolith of Saturn's icy moons. We find that satellite-to-satellite variations and large-scale regional anomalies in microwave signatures primarily reflect different degrees of contamination of the regolith by non-ice compounds. To a lesser extent, they may also point to different concentrations of scatterers in the subsurface; these scatterers must be made of ice and/or void rather than of non-ice contaminants. Enceladus appears to have the cleanest regolith likely due to the geological youth of its surface. Observations also suggest that the current heat flux emanating from this moon is not confined to the South Pole Terrain. In the inner system, the degree of purity of the satellites' regoliths decreases from Enceladus outward likely due to the decrease of the E-ring influx. In the outer system, Phoebe's ring mantles Iapetus' leading hemisphere with a decimetric layer of optically-dark and microwave-absorbent dust. Dione is surprisingly less radar-bright and more emissive than expected from both the observed general trend and the current understanding of its geological history. Another question remains outstanding: why are Saturnian moons, and to a lesser extent Jovian moons, so radar-bright at centimetric wavelengths? Current models assuming purely-random scattering in their subsurface fail to simultaneously reproduce active and passive microwave observations, especially for Saturn's inner moons. This may be due the presence of organized and especially efficient backscattering structures in their subsurface. The challenge is now to identify structures that are geologically plausible.

Thermal Infrared Radiance Transfer Modeling of the Urban Landscape at Ultrahigh Spatial Resolution

The land surface temperature (LST) of urban is a key factor in the field of urban environmental monitoring, and thermal infrared (TIR) remote sensing is an efficient method to obtain it. An important assumption of the traditional thermal radiance transfer model is that the land surface is flat, which has now proven difficult to hold under the urban landscape. Most of the existing urban thermal radiance transfer models have been developed for remote sensing images with a spatial resolution of tens of meters. Currently, airborne TIR sensors have the observation capability to acquire remote sensing images with an ultra-high spatial resolution (1 cm to 1 m), and the model needs to be improved. This paper proposed a new ultra-high spatial resolution urban thermal radiance transfer model (UHURT) after analyzing the transfer processes within the urban canopy at ultra-high spatial resolution. Various radiance components, the emitted radiance, reflected atmospheric downward radiance, and adjacent radiance, were modeled separately. The results of the traditional model and the UHURT model were compared with the results of a ray-tracing computer simulation model, which showed that the new model successfully quantifies the multiple scattering and adjacent effects, and obtained images closer to the computer simulation images. Besides, the LST retrieval of the computer-simulated images was performed using the traditional model and the UHURT model, and the proposed model successfully reduced the errors of the retrieval results and weakened the spatial correlation between the residual distribution and the geometric characteristics of the urban landscape.

Mathematical modeling of vibration drying process taking into account the longitudinal movement of grain material

Purpose. Construction of a mathematical model of non-stationary thermal mass transfer in the drying process in the vibration equipment, taking into account the longitudinal movement of the grain material. Methods. Mathematical modeling methods based on a formalized description in the form of two nonlinear inhomogeneous differential equations of the non-stationary process of drying grain material in a vibrating dryer taking into account longitudinal movement. Results. A mathematical description of the process of drying grain material in a vibrating grain dryer has been formed, taking into account the longitudinal movement of grain in the form of a diffusion mathematical model for determining the distribution of moisture content and material temperature along the length of the vibration transporting support surface. Two-step identification of model parameters based on experimental data is applied. Conclusions. A mathematical description of the nonstationary drying process of grain material in a vibrating dryer taking into account longitudinal displacement is formulated, in the form of two linear inhomogeneous differential equations that can be used to optimize the regime parameters of existing grain dryers. Keywords: drying, grain material, mathematical model, diffusion displacement, moisture content, temperature, speed.

Evolution of temperature and damage in rock mass after heat shock

Heat shock is a feasible means to break rock mass in engineering duo to the large additional thermal stress caused by thermal expansion. This paper established a coupled thermal transfer and rock deformation model based on the energy conservation and the elastic deformation theory of rock. In the model, the failure and damage of rock are judged according to the Drucker-Prager criterion. A finite element method of COMSOL Multiphysics to study the characteristics of temperature, stress distribution and damage zone on a rock surface is proposed. Results show that the failure of rock mass occurs at the cusps of the heater first duo to stress concentration and then grows at both sides of the heater greatly.

Comparative analysis between constant and variable solar radiation reflectivity for exterior walls in the hot-summer and cold-winter zone

Abstract The thermal and optical performance in coating material of exterior walls affected the thermal action from the outdoor thermal environment indirectly, but there was the contrary thermal requirement in winter and summer, which could not be met by the constant-reflectivity coating. To overcome this drawback, the variable-reflectivity coating was analyzed and evaluated by taking three constant-reflectivity coatings as the references. The thermal transfer model with dynamic radiation reflectivity was built to simulate the thermal process of exterior walls in the whole year. Numerical results showed that the constant-reflectivity coating had poor seasonal adaptability with the best performance in some certain months and the poorest behavior in other months, while the variable-reflectivity coating had the better seasonal adaptability to dampen the heat gain in summer and promote the heat gain in winter. Although the variable-reflectivity coating could not show the optimal in all months, its overall performance played the best in the whole year. And compared with constant-reflectivity coating with radiation reflectivity of 90%, 50% and 10%, the variable-reflectivity coating could reduce the annual heating and cooling loads by 2.45%, 16.67% and 46.46%, respectively, in the studied Nanjing City of China.

Emissions from a Domestic Wood Heating Appliance: Experimental Measurements and Numerical Study Using an Equivalent Reactor Network (ERN) Approach Coupled with a Detailed Chemical Mechanism

Dwindling fossil fuel reserves and global climate change drive researchers to discover and develop new strategies to derive energy from renewable sources, such as biomass, including wood. However, when poorly controlled, wood burning can be a source of atmospheric pollution. With the ultimate purpose of better controlling pollutant emissions from domestic small combustion installations, this paper follows two objectives. First, temperature and pollutant measurements obtained at the chimney outlet of a domestic inset fed with wood logs and working under nominal operating conditions are presented. Measured pollutants include CO, CO 2 , nitrogen oxides (NOx), monoaromatic, carbonyl, and phenolic compounds, as well as polycyclic-aromatic hydrocarbons (PAHs) and sugars with measurement made using different types of wood. Second, this paper describes a first attempt of modeling based on a detailed chemistry and tests it for simulating the measured pollutants. The model includes a previously developed detailed chemical kinetic mechanism and a simplified model of thermal transfer in the wood log. A network of ideal reactors (equivalent reactor network (ERN)), for which simulations using the detailed kinetic model are feasible, is proposed to represent both the primary pyrolysis and the combustion of the emitted gaseous species. With only adjusting the parameters used in the model in order to simulate the smoke temperature and the CO 2 mole fraction for a single batch well, simulations give a reasonably good order of magnitude for all of the measured pollutants for the seven used wood batches. A sensitivity analysis of the used parameters and of the structure of the ERN model is also presented.

Numerical Solution of Energy Equation in Porous Channels under Effects of Radiation Field

In this paper, we built a mathematical model for convection and thermal radiation heat transfer of fluid flowing through a vertical channel with porous medium under effects of horizontal magnetic field (MF) at the channel. This model represents a 2-dimensional system of non-linear partial differential equations. Then, we solved this system numerically by finite difference methods using Alternating Direction Implicit (ADI) Scheme in two phases (steady state and unsteady state). Moreover, we found the distribution and behaviour of the heat temperature inside the channel and studied the effects of Brinkman number, Reynolds number, and Boltzmann number on the heat temperature behaviour. We solved the system by building a computer program using MATLAB.

Nonlinear iterative projection methods with multigrid in photon frequency for thermal radiative transfer

This paper presents nonlinear iterative methods for the fundamental thermal radiative transfer (TRT) model defined by the time-dependent multifrequency radiative transfer (RT) equation and the material energy balance (MEB) equation. The iterative methods are based on the nonlinear projection approach and use multiple grids in photon frequency. They are formulated by the high-order RT equation on a given grid in photon frequency and low-order moment equations on a hierarchy of frequency grids. The material temperature is evaluated in the subspace of lowest dimensionality from the MEB equation coupled to the effective grey low-order equations. The algorithms apply various multigrid cycles to visit frequency grids. Numerical results are presented to demonstrate convergence of the multigrid iterative algorithms in TRT problems with large number of photon frequency groups.

THERMAL PERFORMANCE EVALUATION AND ANALYSIS OF THE EFFICIENT and SUSTAINABILITY SHELL AND TUBE HEAT EXCHANGER SYSTEM

Shell and tube heat exchanger (STHE) is one of the most attractive heat exchanger types and widely used in many industrial processes, power generation, and chemical process industries because of the STHE suits the high-pressure applications and harsh environment. STHE porotype consists of a shell with a bundle of tubes and several baffles inside it. The objective of the study is to model and analysis of thermal performance and heat transfer in the advanced STHE system by using ANSYS Fluent along with the experiment. The advanced computational simulation tool, ANSYS Fluent, and AutoCAD were used to model the STHE system along with the one shell (8” diameter), five tubes (1” diameter) and four baffles. In this study, steel was selected for shell materials, copper and brass was compared to select better performance materials for tubes. The constructed STHE model has meshed and analyzed under two mediums (water and biogas) with different thermal conditions. Besides, the experiment results from the STHE prototype were used to investigate conversion efficiency and analyze heat transfer. The analysis of variance (ANOVA) method was used to analyze the significant effect of hot water flow rate and inlet temperature on heat transfer of the STHE prototype. Results from simulation and Karen’s method indicated the heat release of the brass is lower than the copper in the system. Under various operating conditions, experimental results showed the conversion efficiency of the lab-scale STHE is a high range of 0.80-0.86. In addition, ANOVA results indicated that the hot water inlet temperature has a significant effect on heat transfer of STHE prototype.

On the optimization of building energy, material, and economic management using soft computing

This paper provides energy and economic analysis relevant to the cooling season in building enclosures. For a whole year, an Energy Plus thermal transfer model has been created and simulated. Simulations were made from the cities in five different areas of climate in China using weather data files. Energy savings were done from natural cold (e.g., outdoor air), and electricity reductions were performed from air-conditioning electricity devices. This research has investigated the relationship between the cost and building energy while finding a strong and positive correlation. This study has used the Artificial Intelligence (AI) model as Extreme Learning Machine (ELM) and Teaching Learning Based Optimization (TLBO) to calculate the accurate measurement. Three regression models as Pearson correlation coefficient (r), root mean square (RMSE), and coefficient of determination (R2) was used to calculate the results. Following the results of (R2) and RMSE, ELM has shown its higher performance in predicting the strength, energy, and cost of building materials. Based on the simulation results, for office buildings situated in cold areas, the energy savings resulting from phase change materials (PCM) are more prevalent. The test findings demonstrate that the energy savings from PCM applications for the cool area and hot summers and cold winter office buildings were increased. Simple payback time indicated that PCMBs in inhabited buildings could be used costeffectively in a mild temperature environment.

Geometry and adjacency effects in urban land surface temperature retrieval from high-spatial-resolution thermal infrared images

Urban land surface temperature (ULST) is a key surface feature parameter in urban heat island studies. However, the geometry and adjacency effects are usually neglected in conventional land surface temperature (LST) retrieval methods. In this study, considering the geometry and adjacency effects, a new urban canopy multiple-scattering thermal radiative transfer (UCM-RT) model and an urban temperature-emissivity separation (UTES) algorithm were developed for ULST retrieval from Chinese GaoFen-5 (GF-5) satellite thermal infrared (TIR) images. The UCM-RT model and the UTES algorithm incorporate multiple scattering within the urban building canopy and consider the thermal radiance contribution from adjacent pixels and the atmosphere. Two schemes were designed to evaluate the geometry and adjacency effects quantitatively in this study: (1) evaluating their impact on ground temperature and top of atmosphere (TOA) brightness temperature for GF-5 four TIR bands from the simulation dataset, and (2) comparing the retrieval temperature difference between the UTES algorithm and conventional temperature-emissivity separation (TES) algorithm (without considering geometry and adjacency effects). For a specific simulation situation, the magnitude of the geometric effects on urban ground temperatures were found to be approximately 3.2 K, 4.2 K, 4.0 K, and 3.9 K for the four GF-5 TIR bands, while the effects on the TOA brightness temperature reached 2.4 K, 3.3 K, 3.3 K, and 3.0 K for those bands, respectively. The results show that the geometry effects have a significant influence on the thermal radiative transfer process. The temperature error of the UTES algorithm was generally up to 0.8 K, much lower than that of the conventional TES algorithm (~2.2 K) in urban surface. The results indicate that the UTES algorithm is suitable for ULST retrieval, and the retrieval temperature difference between the UTES algorithm and conventional TES algorithm ranges from 0.1 K to 2.1 K, especially for dense building pixels. Additionally, the thermal radiation from adjacent pixels in high-spatial-resolution TIR images has significant influence on ULST retrieval. The comparison between the ULST algorithm for urban land surface and the conventional TES algorithm for the flat surface indicated that the three-dimensional structure inside the pixel has a significant influence on the ULST retrieval. The findings of this study indicate that the geometry and adjacency effects must be considered in ULST retrieval for highly accurate results.

Automated extraction of physical parameters from experimentally obtained thermal profiles using a machine learning approach

Computational modeling is playing an increasingly important role in designing novel experiments and enhancing existing ones. However, these models require input parameters that are sufficiently accurate in order for the predictions to be quantitatively reliable. Frequently, some of these parameters are not directly measurable or have a large uncertainty. We propose a machine learning approach to automatically extract these uncertain or unknown parameters indirectly from experimental measurements that depend on the combination of parameters in a complex manner. The algorithm iteratively refines the possible range of each parameter based on the mean and standard deviation of the sampling simulations that are at the 10th percentile or lower in error until the convergence criteria is met, which is followed by a multivariate quadratic fit and minimization. To demonstrate its applicability, we apply the algorithm to determine physical parameters during the fitting of temperature profiles extracted from in situ synchrotron measurements of an optical floating zone furnace used for high-temperature crystal growth. We built a thermal transfer model in COMSOL Multiphysics® software that considers an Al2O3 sample that is heated by a power source and thermal conduction and cooled due to natural air convection and thermal radiation. A set of experimentally measured steady-state temperature profiles of a heated Al2O3 sample is used as training data to determine the parameter set using the algorithm, which resulted in a close match. Using this parameter set, we also simulated the time-dependent temperatures, which yielded good agreement to the corresponding experimental measurement. We conclude that the steady-state temperature profiles suffice as training data, eliminating the need for additional in situ measurements of the dynamic experimental state for robust model parameterization.

Inclination angles on the thermal behavior of Phase-Change Material (PCM) in a cavity filled with copper foam partly

In this study, the influence of the inclination angle was analyzed on the thermal behavior of PCM in the cavity filled with copper foam fins. Twelve inclination angles from 0° to 360° were studied for the thermal storage unit, while the two-temperature equation thermal transfer model was built. The liquid fraction, the temperature response rate, and the average heat flow were employed as evaluation parameters. Numerical results displayed the inclination angle had the great influence on the PCM thermal performance and by optimizing the inclination angle, the whole phase-change time was shortened by 43.16% with the inclination angle from 0° to 180°. In melting and freezing processes, the inclination angle had the opposite rules and affected the thermal performance difference obviously. With the inclination angle from 0° to 180°, the difference values were reduced from 17904s, 712 w/m2 and 0.00867 °C/s to 1709s, 31 w/m2 and 0.00051 °C/s for full phase-change time, the average heat flow and temperature response rate, respectively. And the optimum inclination angle was 180° in the view of a melting and freezing period and the reasonable inclination angle could be selected according to thermal storage and release rules in the engineering application.

A novel model of fractional thermal and plasma transfer within a non-metallic plate

While in several publications the thermo-viscoelastic properties of solids have been documented, no attempt has been made to examine the action of coupled thermal and plasma wave in viscoelastic materials. In this paper, a new mathematical model for thermal and plasma transfer in an organic semiconductor was constructed with a time-fractional derivative of order

The performance analysis on a novel purified pv-trombe wall for electricity, space heating, formaldehyde degradation and bacteria in activation

On the one hand, PV-Trombe wall is a combined solar system that meets dual functions of space heating and electricity output, but the utilization on the recovered solar heat by PV-Trombe wall is very limited. On the other hand, thermal catalytic oxidation and thermal sterilization are two advanced air purification technologies and both they have huge application potential with solar heat. Therefore, a novel purified PV-Trombe wall for electricity, space heating, formaldehyde degradation and bacteria inactivation was proposed. Firstly, the system thermal and mass transfer model was established and verified by experimental data. Secondly, the comprehensive performance with the PV coverage ratio of 0 was analyzed. Finally, the effect of PV coverage ratio on the system performance was investigated. Accordingly, the main results were: ① Under PV coverage ratio of 0, the average daily air thermal efficiency and formaldehyde single-pass ratio were 0. 46 and 0. 35, respectively. Meanwhile, the total generated volume of clean air by formaldehyde degradation was 93. 4 m3 . Five kinds of bacteria were fully thermal inactivated for several hours. Accordingly, the total generated volume of clean air were 188. 3, 173. 0, 201. 4, 189. 9 and 200. 2 m3 for E. coli, L. monocytogenes, L. plantarum, S. Senftenberg and S. cerevisiae, respectively. ② The PV coverage ratio played a different role on the system comprehensive performances. For specific performances, the PV coverage ratio only had a positive influence on electrical performance and had negative effect on other performances such as thermal, formaldehyde degradation and bacteria inactivation performances. However, considering the system comprehensive performances, the electrical energy was the additional product and the low PV coverage ratio was suggested. ③ The works could provide possible support to the prevention and control of COVID-19. © 2021, Editorial Department of Journal of University of Science and Technology of China. All rights reserved.