Indoor Heat Sources Research Articles

Simulation of indoor space thermal energy circulation in architectural environment design detail features based on visual object tracking algorithm

The heat circulation of interior space plays a crucial role in the design of the built environment, affecting energy efficiency and residential comfort. With the development of science and technology, visual target tracking algorithm provides a new possibility for optimizing thermal energy cycle. The purpose of this paper is to study the simulation method of indoor space thermal energy cycle based on visual target tracking algorithm to improve the efficiency of thermal energy management in building environment design and ensure indoor comfort. The research uses laboratory Settings, combined with high-performance cameras and advanced visual target tracking algorithms, to monitor indoor heat source distribution and personnel movement in real time. Through data acquisition and analysis, the indoor heat cycle model was constructed and simulated by computational fluid dynamics (CFD) software to evaluate the influence of different design parameters on the heat cycle. Through the optimization of the design scheme, the efficiency of indoor heat use is significantly improved, and the comfort score of residents is significantly improved. Therefore, the simulation of indoor space thermal energy cycle based on visual target tracking algorithm provides an effective tool for building environment design, which can realize efficient energy management and improve living comfort.

Study on the optimal layout of roof vents and rooftop photovoltaic of the industrial workshop

Roof vents are crucial for facilitating natural ventilation within industrial workshops. However, their substantial size and height can limit available roof space and create extensive shadow areas, thereby impeding the installation of photovoltaic (PV) systems on industrial roofs. This study quantitatively assesses the influence of roof vent positioning, morphology, and roof architecture on the natural ventilation efficiency of workshops with varying indoor heat sources. Subsequently, the study evaluates how different vent configurations affect the installable area for rooftop solar panels. Findings suggest that shifting from traditional roof ridge vents directly above a heat source to north-side vents inclined towards the roof can marginally decrease the ventilation flow rate by approximately 5 %, translating to a minor temperature rise of around 0.46 °C within the occupied zone. Nonetheless, the Predicted Mean Vote (PMV) thermal comfort indices remain consistent across scenarios. Notably, adopting north-side vents, either flush with the roof or inclined, can enhance the annual energy yield of the rooftop PV system by 15.49 % and 22.67 %, respectively, under equivalent solar irradiation. Thus, strategic adjustments to vent positioning, form, and roof design can substantially boost the photovoltaic system's power output without compromising the workshop's natural ventilation performance.

Indoor thermal nonuniformity of atrium-centered public building: Monitoring and diagnosis for energy saving

Heating ventilation and air conditioning system accounts for over one third of building energy usage, especially for public buildings due to large indoor heat source and high ventilation and thermal comfort requirement compared to residential buildings. Natural ventilation shows high application potentials in public buildings because of its high-efficient ventilation effect and energy saving potential for indoor heat dissipation. In this paper, the building design is conducted for a science museum and library with atrium-centered natural ventilation consideration. The floor layout, building orientation and internal structure are optimized to make full use of natural ventilation for space cooling under local climatic conditions. A natural ventilation model is established through building field tests to evaluate the air flow and thermal environment under indoor and outdoor pressure differences. The preliminary results show that Building A's courtyard exhibited overheating issues, likely attributed to outdoor solar radiation, whereas Building B's courtyard experienced localized cooling, possibly due to indoor air conditioning system controls. Addressing these concerns necessitates modifications in courtyard design and structure. Moreover, both courtyards displayed vertical temperature gradients, emphasizing the need for effective management of outdoor heat influx and enhancements in indoor ventilation and shading strategies. To mitigate these issues, the study proposed three distinct roof design models and more refined indoor air conditioning system control strategies. The optimization of architectural design can achieve a maximum energy-saving rate of 46.54 %. Furthermore, aligning functional zones with thermal comfort areas was recommended to enhance overall building thermal comfort. The findings and proposed solutions from this study are anticipated to contribute to the enhancement of thermal comfort, energy efficiency, and vertical temperature distribution in large public buildings, catering to user requirements while reducing energy consumption. This research holds significant implications for advancing sustainability and environmental preservation in the realm of architecture.

Natural Ventilation for Cooling Energy Saving: Typical Case of Public Building Design Optimization in Guangzhou, China

Heating ventilation and air conditioning systems account for over one-third of building energy usage, especially for public buildings, due to large indoor heat sources and high ventilation and thermal comfort requirements compared to residential buildings. Natural ventilation shows high application potential in public buildings because of its highly efficient ventilation effect and energy-saving potential for indoor heat dissipation. In this paper, a building design is proposed for a science museum with atrium-centered natural ventilation consideration. The floor layout, building orientation, and internal structure are optimized to make full use of natural ventilation for space cooling under local climatic conditions. The natural ventilation model is established through computational fluid dynamics (CFD) for airflow evaluation under indoor and outdoor pressure differences. The preliminary results show that such an atrium-centered architectural design could facilitate an average air exchange rate over 2 h−1 via the natural ventilation effect. Moreover, indoor thermal environment simulation results indicate that the exhaust air temperature can be about 5 °C higher than the indoor air mean temperature during the daytime, resulting in about 41.2% air conditioning energy saving ratio due to the free cooling effect of natural ventilation. This work can provide guidance and references for natural ventilation optimization design in public buildings.

Experimental investigation on thermal performance of underground refuge chamber under natural convection and ventilation

Thermal performance of densely populated underground buildings is normally influenced by various factors, including the surrounding rock (SR), ventilation, and indoor heat sources. It is recognized that little experimental studies on thermal control for the above building was reported. In this article, a full-size 50-person mine refuge chamber (MRC) was newly constructed to test the thermal performance under natural convection and ventilation. The heat ducts were used to simulate the heat released from human body. Experimental results indicated that: (1) the intensity of the heat transfer between rock and air increases with the rise in heat source rate and ventilation temperature (VT), while it decreases as the initial surrounding rock temperature (ISRT) increases; (2) when considering the joint temperature control of pre-cooled SR, it is recommended to reduce the VT linearly during the evacuation period in order to ensure the thermal safety of personnel. During the non-refuge period, the cold amount should be stored as far as possible into the shallow SR body to make full use of it; (3) to ensure the thermal safety of an MRC with a capacity of 30 people for 96 h, cooling measures are required when the ISRT exceeds 21.3 °C. In addition, when the ISRT reaches 27.6 °C, the per capita ventilation is 0.19 m3/min, and the temperature is 26 °C, which can also meet the requirements. This study provides experimental verification as a basis for future research on underground space temperature control considering the influence of SR.

Various disturbances propagation analysis of district heating system based on the standardized thermal resistance method

AbstractVarious heating disturbances and faults in the heating network are necessary to be controlled and handled by some intelligent heating strategies with the increasing complexity of the heating network. This paper constructed the dynamic modeling of the heating system using standard thermal resistance and obtained a dynamic heat current model of the heating system. On this basis, we analyzed the heat transfer performance of the heating system. Five disturbances are selected, including the behavior of users, indoor heat source, heat exchanger heat transfer performance deterioration, pipe blockage, and pipe leakage. The effects of different disturbances on the overall system and user side water supply temperature were obtained by establishing a dynamic model for segmented heating pipelines. Feasible control methods for the heating network and load side are sorted out, mainly changing the water supply's temperature and the water supply's flow rate to reduce the water supply's fluctuation. Five specific control strategies are proposed for five types of disturbances. Comparing the case without control and the case with control, the results show that the fluctuation of water supply temperature is significantly reduced, and the control strategies can reduce the impact of disturbances on the heat network system and customers and improve the comfort of customers in the presence of disturbances. under the disturbance of pipeline leakage, the method proposed in this article reduces the temperature fluctuation amplitude by 75% and the fluctuation duration by 60%.

CFD modeling of room airflow effects on inactivation of aerosol SARS-CoV-2 by an upper-room ultraviolet germicidal irradiation (UVGI) system

Ultraviolet germicidal irradiation (UVGI) systems inactivate microorganisms indoors. Upper-room UVGI systems use wall- or ceiling-mounted fixtures to create an air disinfection zone above the occupied zone. The performance of upper-room UVGI systems varies with indoor airflow patterns induced by mechanical ventilation and thermal plumes from indoor heat sources. Little information is available on the effects of ventilation strategies on upper-room UVGI system performance for the control of viral aerosols in occupied spaces. This study simulated the effects of ventilation system characteristics in an office space on the ability of an upper-room UVGI system to inactivate viral aerosols with UV-C susceptibility representative of coronaviruses. UVGI reduced viral aerosol concentration by two orders of magnitude relative to the concentration without UVGI. Air change rates and air distribution strategy (mixing vs. displacement) had notable effects on the effectiveness of the UVGI system. For mixing ventilation, as the recirculation airflow rate increased from 0 to 5.3 h−1 for a room volume of 108 m3 with a fixed outdoor air change rate of 0.7 h−1, UVGI inactivation increased by 96.7%. Mixing ventilation with 100% outdoor air of 0.7 h−1 yielded airborne virus inactivation that was double that of displacement ventilation, due to enhanced air mixing.

Analysis of the Ventilation Performance of a Solar Chimney Coupled to an Outdoor Wind and Indoor Heat Source

The effects of different solar radiation intensities, heat flow density of indoor heat sources, outdoor wind speed, and the relative location of indoor heat sources on the natural ventilation performance of solar chimneys are investigated through three-dimensional numerical simulations. The mechanism of the mutual coupling of the solar chimney effect with the outdoor wind and indoor heat source heat plume is explored. The results of the study show that when the structural parameters of the solar chimney are the same, the heat flow density on the surface of the indoor heat source, the outdoor wind speed and the solar radiation intensity all have a gaining effect on the ventilation performance of the solar chimney and the effects of the three on the ventilation of the solar chimney promote each other, when the solar radiation intensity is 200 W/m2, the outdoor wind speed is 1.0 m/s, and the indoor heat source heat flow density increases from 0 to 1 500 W/m2, the solar chimney ventilation volume increases from 0.393 m3/s to 0.519 m3/s, the maximum value of the increase is 32.1%. In the other two cases, the maximum increase in solar chimney ventilation is 176.7% and 33.1%, respectively. Under the same conditions, solar chimney ventilation is optimal when the heat source is in the middle of the room. The presence of outdoor wind, however, affects the optimum design parameters of the solar chimney. Compared to the case where no outdoor wind is taken into account, the optimum inlet width of 0.2–0.3 m for the solar chimney no longer applies with outdoor wind, with the optimum value rising to 0.5 m.

COVID-19 바이러스의 확산에 대한 에어컨 기류의 영향 분석

This study analyzed the transmission mechanism of viruses according to operating conditions of air conditioners in small restaurants using CFD based on the actual occurrence situation. COVID-19 virus (SARS-CoV-2) is known to be spread through droplets. However, in a closed environment, after some period of time, droplets become dry and fine particles (aerosols) that can be transmitted in air. The spread of virus-laden aerosols with or without air-conditioner operation was analyzed by three-dimensional CFD simulation taking into account the heating effect of human body and thermal effect of an indoor heat source (e.g., food in a heated pot). Results showed that air currents of air-conditioners diffused virus-laden aerosols indoors and the return airflow of air-conditioner re-diffused the contaminated air throughout the room. Especially, when the airflow hit a structure, it created a vortex and built up high concentrations of pollutants due to accumulation. On the other hand, pollutant concentrations were low around areas of fresh air inflow (infiltration). These results imply the importance of ventilation.

Study on ventilation performance of inclined solar chimney coupled with indoor heat source

The study of ventilation air distribution of the building with built-in heat source and set inclined solar chimney is carried out through 3D numerical simulation. The synergistic effect of thermal plume formed by internal heat source and solar chimney effect is analyzed. The effects of different solar radiation intensity I, heat flow density W at the surface of the internal heat source and structural parameters (including the height of the internal heat source from the ground h and the mezzanine inlet spacing b) on the indoor natural ventilation performance of the building are investigated.

Simulation of thermal and humid environment of rural residence envelope inner surface during the plum rains season in Changsha China

The Plum Rains Season (PRS) has the typical characteristics of outdoor air temperature dramatic changes and high air humidity in the hot summer and cold winter region in China. Even if the indoor heat source and moisture production is constant, when the outdoor air temperature rises rapidly during high air humidity PRS, the building envelope temperature heats up much more slower than the indoor air temperature and therefore the wall surface temperature is lower than the indoor air dewpoint which leads to condensation phenomenon, resulting in deterioration of insulation performance, mouldy walls, deterioration of indoor air quality. At present, there is a lack of research on the factors affecting condensation in rural residence during PRS. This paper evaluates the impact of occupants’ habit of window opening modes and building construction parameters on the building envelope surface condensation in Changsha during PRS. Using Designer'Simulation Toolkit (DeST) simulated and analysed the impact of key parameters such as window-to-wall ratio, exterior wall reflectivity, window opening mode (open/close), and external wall insulation on the building indoor thermal and humid environment. The condensation risk X is proposed to evaluate the condensation possibility on the building envelope's inner surface. The results show that from the perspective of anti-condensation: The rural residential building in Changsha should balance the window-wall ratio against better natural lighting; Keeping windows closed during PRS can effectively alleviate the condensation problem while the insulation in the external wall layer could aggravate the condensation.

A transfer function model of lighting heat dissipation for detecting time-delay effect and dynamic cooling demand during the real-time operation of buildings

Monitoring real-time heat dissipation of lighting, a major indoor heat source, is essential for determining the dynamic cooling demand of buildings, and it provides a reliable basis for sizing air-conditioning systems and saving energy. Contemporary models cannot be used to obtain the accurate real-time heat dissipation of lighting or the time-delay effect, because of which these models have critical limitations in precisely detecting dynamic cooling demand of buildings. To address this problem, a transfer function model is proposed for calculating the real-time heat dissipation of lighting in this paper. First, the model structure is determined according to the energy conservation law, heat transfer principles, and so on. Second, an experiment is conducted using a nearly adiabatic test chamber. Third, parameter identification and order reduction analyses are performed, and the real-time heat dissipation model of lighting is determined as a third-order transfer function. Experimental data of the same and different types of lighting are employed to verify the proposed model, and the maximum mean absolute percentage error (MAPE) is 7.83%. Comparing with the fixed ratio method, the proposed transfer function model not only reduces MAPE by 66.05% within 1 h after lighting is turned on but also describes a time-delay effect in the stability of lighting heat dissipation. The results of this study exhibit the promising applicability for accurately determining the cooling demand of a building during real-time operation, thus improving the indoor thermal environment and reducing energy consumption.

Analytical expression of dynamic cooling load of non-uniform environment considering the thermal mass of convective boundaries

Conventionally, the cooling load of an indoor environment is calculated using a lumped model. For non-uniform environment, previous research has revealed how steady-state cooling load is influenced but currently, no theory on the dynamic cooling load of a non-uniform environment has been conducted because of the thermal mass of convective boundaries. To establish the analytical expression of dynamic cooling load of non-uniform environment, the inner surface temperature of convective boundaries is used as an intermediate variable in this study. The relationship between the convective heat gain and the inner surface temperature of convective boundaries, indoor heat sources has been built. After solving the transient heat transfer of building thermal mass by differential method, the inner surface temperature of convective boundaries, as well as the dynamic local cooling load can be obtained. The dynamic cooling loads of different airflow patterns and target zones are compared through case studies at last. The results show that: 1) when the flow field is fixed, there exists linear relationship between convective heat gain and setpoint of the local zone, temperature of other convective boundaries, and indoor heat sources, and three indices such as equivalent heat transfer coefficient , contribution of other convective boundary and contribution of heat source are proposed correspondingly to reflect the effect of each factor; 2) the proposed indices are constant for a specific airflow pattern when the flow field and location of the target zone are fixed, and the equivalent heat transfer coefficient of the external wall is 4.2 and 2.9 W/(m 2 ·K) as an example for the cases of mixing ventilation and displacement ventilation , respectively; 3) the thermal mass of the building envelope has a significant effect on the dynamic convective heat, and the fluctuation of the cooling load could be overestimated through steady-state calculation, as shown in the displacement ventilation case, the peak value of the dynamic cooling load is 76.8% of that obtained through steady-state calculation. • Convective heat of boundary is calculated by the temperature of target zone. • Temperature of other boundary and indoor heat source contribute to the convective heat of a boundary. • Theoretical expression for dynamic cooling load in a non-uniform environment is derived. • Thermal mass has a significant effect on the local cooling load of non-uniform environment. • Peak heat gain of advanced airflow pattern is 76.8% of the mixing ventilation.

Development of a second-order dynamic model for quantifying impact of thermal mass on indoor thermal environment

Indoor thermal environment can be significantly influenced by thermal mass, which is not considered quantitatively in building thermal design due to the lack of a simple and accurate calculation model. For this reason, a temperature elastic coefficient (TEC) is proposed to characterize the dynamic heat transfer between inner surfaces of external walls (ISEW) and indoor air, and an effective thermal capacity (ETC) is used to characterize thermal mass. A second-order dynamic model is thus developed to efficiently evaluate the impact of thermal mass on indoor thermal environment by employing the TEC and ETC. The results show that both the TEC and the ETC are affected by the insulation position, wall thermal resistance, air change rate and window-wall ratio (WWR), but independent of the outdoor air temperature, indoor heat source intensity and solar radiation. Furthermore, the combination of the second-order dynamic model and the database models of ETC and the TEC are determined by using multiple nonlinear regression analysis, and can help policy makers and building thermal designers to estimate the impact of thermal mass on the indoor thermal environment quickly and accurately.

Experimental study on indoor thermal environment of industrial building spaces enclosed by fabric membranes

Nowadays with the development of science, many new technologies are being introduced to the fabric membrane material fields. Membrane structures have been widely used in industrial storage buildings to reduce the dust pollution from open storage depots. But the thermal environment of these buildings is poor due to its light weight and low thermal resistance. It is worth exploring appropriate measures to study this problem. Therefore, a monitoring platform was established in order to study the indoor thermal environment of the industrial storage building with membrane structure. The solar radiation heat model was established using MATLAB program based on the theory of thermal transfers. And studied the impact of the outdoor temperature and solar radiation intensity in the heat transfer characteristics of membrane material. The indoor air temperature distribution of the buildings was also analyzed. The results show that solar radiation has a significant effect on the surface temperature of the fabric membrane material. The solar radiation of different intensities incident on the surface of the fabric membrane causes its surface temperature to fluctuate rapidly and significantly. Without indoor heat source, the indoor thermal environment is mainly affected by the solar radiation heat exchange of the fabric material.

Comparison of space cooling/heating load under non-uniform indoor environment with convective heat gain/loss from envelope

The indoor parameters are generally non-uniform distributed. Consequently, it is important to study the space cooling/heating load oriented to local requirements. Though the influence of indoor set point, heat sources, and ambient temperature of convective thermal boundary on cooling/heating load has been investigated in the uniform environment in previous research, the influence of these factors, particularly the convective heat gain/loss through a building envelope, on cooling/heating load of non-uniform environment has not yet been investigated. Therefore, based on the explicit expression of indoor temperature under the convective boundary condition, the expression of space cooling/heating load with convective heat transfer from the building envelope is derived and compared through case studies. The results can be summarized as follows. (1) The convective heat transferred through the building envelope is significantly related to the airflow patterns: the heating load in the case with ceiling supply air, where the supply air has a smaller contribution to the local zone, is 24% higher than that in the case with bottom supply air. (2) The degree of influence from each thermal boundary to the local zone of space cooling cases is close to that of a uniform environment, while the influence of each factor, particularly that of supply air, is non-uniformly distributed in space heating. (3) It is possible to enhance the influence of supply air and heat source with a reasonable airflow pattern to reduce the space heating load. In general, the findings of this study can be used to guide the energy savings of rooms with non-uniform environments for space cooling/heating.

Thermal Performance of Phase Change Material Wallboard with Typical Structure: Artificial Controlled Condition Experimental Investigation

Phase change material (PCM) integrated with building envelopes could enhance thermal storage performance of building envelopes significantly. Due to the variable physical property of PCM, the thermal performance of PCM envelopes is different from traditional envelopes such as clay brick and concrete wall. In the present paper, the thermal performance of PCM envelopes are experimentally investigated in an artificial climate chamber. The experimental PCM wallboard is made by PCM layer, concrete layer and insulation layer, which could reflect the real envelopes structure in typical office buildings in Western China. The thermal performance of the wallboard with different material layer locations is compared, and the thickness of PCM layer is optimized. During the experiments, the PCM wallboard is under double-sides heat effect, including periodic outdoor air temperature fluctuation and indoor heat source. Two indicators named thermal inertia index and coefficient of heat accumulation of interior surface are introduced as the key parameters to evaluate the thermal storage performance of the PCM envelopes. The results show that, under double-sides periodic thermal effect, the indoor air temperature is mainly affected by the coefficient of heat accumulation of interior surface of the PCM wallboard. However, the increment of the thermal inertia index of the whole wallboard has little influence on the indoor thermal environment under double-sides periodic thermal effect.

High-Resolution CFD and In-Situ Monitoring Based Validation of an Industrial Passive Air Conduction System (PACS)

Natural driven ventilation is a widely used technique in hot and arid climate, but it is rarely known that it can lead to significant energy saving in a moderate climate too. In this paper, an existing building is presented that was designed with a passive air conduction system (PACS), where wind and buoyancy effects induce air to be exchanged without external energy needs. The aim is to show that the design methodology, using numerical simulation to give accurate results, is able to use them in further developments. Due to this design process, the specific building possesses numerous special properties, including airflow accelerating elements, solar-heated “chimneys”, and the indoor heat sources coming from the industrial technology. As the building has been constructed and was equipped with around 750 sensors (integrated and manual), it is possible to analyze the ongoing physical phenomenon in a highly detailed way and to collect the experienced dataset for further investigations. The current study carries out a complex validation of the design and the used numerical methods to give general design rules for further PACS design and support following investigations, e.g., occupant comfort prediction or latent heat storage calculation. The experiences showed that the developed computational fluid dynamics technique gives a below 99% accuracy in the velocity and the temperature field, and approximately 85% accuracy in the volume flow values, resulting in a good prediction for aerodynamic characterization of buildings, i.e., passive ventilation air exchange rate.

Implementation of demand-oriented ventilation with adjustable fan network

Airflow patterns are essential for heating, ventilation and air conditioning (HVAC) systems. Traditional HVAC systems are predesigned and operated using a fixed airflow pattern. However, the indoor occupancy and heat source always vary and therefore, the fixed flow pattern cannot efficiently maintain the required indoor environment conditions. In this study, a novel Adjustable Fan Network (AFN) for improving airflow pattern manoeuvrability is proposed. It integrates multiple small and adjustable axial fans into an AFN, enabling it to change the airflow pattern based on the actual demand with only one set of equipment. Further, the outflow characteristics of two types of axial fans were measured using a quad-view colour sequence particle streak velocimetry (CSPSV) in a test chamber. The ventilation system was then designed based on typical scenarios. Finally, the performance of the AFN was evaluated under different scenarios using a quad-view CSPSV. Based on the results, it was evident that the AFN can provide a better direct supply of air to the occupied zone under different scenarios. With the growing demand for personal thermal comfort and energy-saving in HVAC systems, the novel AFN system has a great potential to be a highly controllable terminal for demand-oriented ventilation.

Comparison and analyses of two thermal performance evaluation models for a public building

Abstract Recently, investigations on building thermal inertia are mainly involved with the materials of the building envelope. Usually, other influencing factors are ignored, such as room ventilation, indoor heat storage, indoor cold source, indoor heat source and human behavior. In this paper, two models based on thermodynamics are given to evaluate building thermal performance. One is thermal mass model, and the other one is thermal reserve coefficient model. Based on thermal response testing data in a non-heating season, the thermal mass model was adopted to classify the envelope type, and the delay rules between the indoor temperature and the outdoor meteorological parameters are analyzed. In a heating season, the delay rules among the outdoor temperature, indoor temperature and supply water temperature are obtained by changing the supply water temperature. Thermal performance of the targeted building is evaluated with the thermal reserve coefficient model. For the same public building, two evaluation models tend to be consistent. These two evaluation models presented in this paper can be applied for the optimal design of buildings envelope.