Building Indoor Thermal Environment Research Articles

Performance evaluation and multi-objective optimization of a tubular indirect evaporative cooler integrated with moisture-conducting fibers

Indirect evaporative cooling (IEC) technology is an energy-efficient approach for regulating the indoor thermal environment of buildings. The conventional tubular indirect evaporative cooler (TIEC) may have a relatively low cooling efficiency due to poor wettability issues. The application of moisture-conducting fibers provides a feasible way to solve the above problem. However, the integration of moisture-conducting fibers with TIEC is still in the exploratory stage. This study proposed a novel moisture-conducting fiber-assisted TIEC and conducted a multi-objective optimization. An experimental facility and theoretical model of the proposed moisture-conducting fiber-assisted TIEC were developed. Based on the numerical model validated by experiments and response surface methodology (RSM), the regression models for performance prediction of the cooler were established. Eight input parameters including inlet air parameters, operating parameters and geometric parameters were selected, and four performance evaluation indicators were chosen as output responses. The parameter sensitivity of the regression models was analyzed. The multi-objective optimization was performed by considering the influence of different relative weights assigned to the output responses. Furthermore, the performance of the optimized cooler applied in different climate zones was predicted. The results showed that the product air temperature drop could achieve 8.8–11.3 °C after cooling by the cooler. The established regression models can predict the performance of the moisture-conducting fiber-assisted TIEC conveniently and effectively, which is expected to guide the design and optimization of engineering practices.

Study on the method of determining indoor radiant temperature under strong radiant heat source

How to obtain the mean radiant temperature and radiant temperature asymmetry more accurately is the basis for the study of the indoor thermal environment under the influence of external windows. It is also a prerequisite for the field study of the indoor thermal environment of buildings. This study conducted a field experiment on the suitability and limitations of different methods for determining indoor mean radiant temperature and radiant temperature asymmetry under the strong radiant heat source caused by short-wave radiation. It was found that the mean radiant temperature and the radiant temperature asymmetry obtained by measuring the surface temperature of the enclosed space could better reflect the real indoor long-wave radiation situation. Methods based on the black globe temperature and net radiometer were both affected by the solar short-wave radiation. The results of this study could provide a theoretical basis for the impact of windows on the indoor thermal environment.

Building envelopes with radiative cooling materials: A model for indoor thermal environment assessment based on climate adaptation

To create a comfortable thermal environment in buildings, building cooling account for a large part of building energy consumption in summer. The spectral radiative properties of radiant cooling materials as a passive cooling technology have been extensively studied. However, there are few studies that address the application of radiant cooling materials to building envelopes. This paper proposed a radiative cooling glass composite structure for windows based on existing radiant cooling materials and established a climate adaptive radiant cooling building indoor thermal environment assessment model. This assessment model combines the spectral selectivity of radiative cooling materials with climate characteristics. An indoor thermal environment test system and an ambient climate measurement system are designed under the influence of external windows, and the average error of the assessment model is verified to be no more than 4.83%. Based on this assessment model, three applicability analyses were conducted: Firstly, it is concluded that the daytime indoor temperature with radiative cooling glass (RCG) is 26.43°C lower than that with the ordinary glass. Secondly, RCG can effectively improve the indoor thermal environment for rooms facing each direction, and the indoor temperature is 45.06°C lower than that of ordinary glass in the east and west directions, and 15.05°C lower than that of ordinary glass in the north and south directions. Finally, analysis of the correlation between indoor temperature and outdoor temperature shows that the indoor temperature tends to rise as the outdoor temperature rises. The analysis of the application of RCG in different cities shows that the performance of radiative cooling is relatively weak in areas with high relative humidity.

Experimental and numerical study on indoor thermal environment of solar Trombe walls with different air-channel thicknesses in plateau

Trombe wall is an effective method for passively absorbing solar energy and providing heat to buildings. This paper conducts a comparative experiment between Trombe wall buildings and glass curtain wall buildings during the winter season in Songpan County, western Sichuan. The climate characteristics of the western Sichuan plateau are analyzed, and the potential applications of these two building types in the region are investigated. To further understand the heat transfer mechanism of Trombe wall buildings, numerical simulations are carried out to analyze the indoor thermal environment of buildings with varying air channel thicknesses. The results show that Trombe wall buildings are more effective at delaying heat loss compared to glass curtain wall buildings, due to the thermal storage of the Trombe wall providing heat at night. This makes Trombe wall buildings well-suited for regions with strong solar radiation and large temperature differences between day and night, such as the alpine region. However, excessively small air channel thickness can lead to excessive air flow speed during the day, causing more heat loss and weaker insulation at night. Conversely, excessively large air channel thickness reduces air flow temperature difference and diminishes the heat brought into the room. Among different air channels, a thickness of 100 mm performs best with a temperature difference between the inlet and outlet of about 45 °C. At 13:00 o ‘clock, the maximum airflow rate of approximately 5.8 L/s is achieved for a thickness of 100 mm, whereas for thicknesses of 150 mm and 50 mm, the corresponding values are 4.9 L/s and 4.1 L/s, respectively. It is important to note that blindly increasing air channel thickness to raise indoor temperature is not a practical or reasonable engineering solution. The measured and numerical results can provide valuable reference value for the improvement and development of Trombe wall buildings in the future.

A novel MOF/RGO-based composite phase change material for battery thermal management

Despite being an advanced material widely used in solar energy harvesting, indoor thermal environment of buildings and other fields, the phase change material (PCM) still suffers from the low thermal conductivity and high melt flow rate in practical applications in battery thermal management system. Against this background, a novel anti-leakage and thermally induced high thermal conductivity composite phase change material (CPCM) was proposed and prepared, and it was filled into a lithium-ion battery pack, and then the thermal management effects of the metal organic framework (MOF) based CPCM in the battery module under different conditions of harsh working environment were experimentally studied. The research results indicate that the new CPCM achieves better thermal management performance than natural convection under all test conditions. For example, under the worst test condition of 40 °C ambient temperature and 3 C discharge rate of battery module, the maximum temperature (Tmax) and maximum temperature difference (ΔTmax) in CPCM cooling module were 63.53 °C and 5.33 °C respectively, which are 23.47 °C and 6.67 °C lower than that of natural air cooling module. Interestingly, when the discharge rate was constant at 3 C, the ΔTmax in the discharge process of the battery module decreased with the increase of the test temperature, which was completely opposite to that of the natural air cooling module. It was helpful to improve the temperature consistency of the battery module. Finally, the novel CPCM has achieved better thermal management performance after comparison analysis.

Association between thermal comfort and cortisol depends on the air temperature and exposure time

Exploring the link between thermal comfort and cortisol, a stress hormone, at different air temperatures can give a theoretical basis for creating a comfortable and healthy indoor environment, although the relationship is not yet obvious. We considered three temperatures and two exposure levels, collected the subjects' subjective evaluations and saliva, detected the concentration of cortisol in saliva, and analyzed the change characteristics of subjective evaluations and cortisol concentration at different temperatures with exposure time and their relationships at different exposure times. Subjective evaluations were better and cortisol concentration was lower at neutral temperature, according to our findings. Furthermore, there was a U-shaped distribution of cortisol concentration with thermal sensation vote (TSV), and cortisol concentration decreased with increasing thermal comfort vote (TCV). In comparison to “hot” and “cold,” the concentration of cortisol corresponding to “neutral” after 30 min of exposure declined by 179.0% and 59.3%, respectively; the concentration for “very uncomfortable” was higher by 191.4% than for “comfortable.” Following a 60-min exposure, the concentrations that corresponded to “neutral” and “very uncomfortable” were, respectively, lower by 89.3% and 143.0% than “hot” and “comfortable.” Our findings suggest that cortisol derived from human saliva may be a novel and useful objective indicator assessing human thermal comfort. This study can deepen our understanding of the relationship between human thermal comfort and stress hormones, and relevant conclusions provide theoretical basis for building indoor thermal environment.

Occupants’ Responses to Naturally Ventilated Buildings in Northern Guizhou, China

With the acceleration of urbanization, suggestions that are based on findings gathering from field studies on building refurbishment, new building design and building operation and maitenance are essential to achieve building energy saving and carbon emmision target. Therefore, a field investigation on thermal comfort and adaptive responses of occupants in naturally ventilated buildings were conducted during winer time in Zunyi. Without central heating system supply, the mean value of indoor air temperature is 14.86°C. But more than half of occupants (57.9%) who were satisfied with surrounding thermal environment. People are active to utilize various strategies to restore thermal comfort of their own. Adjusting clothing levels and using heating devices (e.g. fan heater, portable hand warmer, etc.) are the most popular adaptive behaviours helping them alleviate thermal discomfort caused by lower and humid thermal environment. The aPMV model is developed with adaptive coefficient of -0.33. The findings obtained from this investigation fill gaps in similar researches in northern Guizhou and provide guidelines on building indoor thermal environment improvement considering passive design strategies in this area.

Experimental investigation on the thermal performance of a novel radiant heating and cooling terminal integrated with a flat heat pipe

Intermittent heating and cooling are energy efficient measures for building indoor thermal environment, and improvements to the thermal response speed of the indoor terminal are particularly important for thermal comfort. In this study, a novel integrated flat-heat-pipe radiant heating and cooling terminal was proposed. The flat-heat-pipe is used as the radiant panel in this terminal, providing a quick thermal response speed and high thermal uniformity. Moreover, the proposed radiant terminal could also be operated in both winter and summer owing to its integrated flat structure. In this study, an experimental rig was built for studying the thermal performance of the flat heat pipe terminal, including the heat response speed, heating/cooling capacity, heating/cooling temperature, and heat transfer coefficient. The experimental results show that the heating/cooling response speed ranges from 550 s to 1810 s and the vertical temperature difference is less than 1.4 °C/m. In addition, the heat transfer capacity showed a significant increase of 36.1% to 42.6% when the emissivity of the surface of the flat heat pipe increased from 0.1 to 0.9. The heating/cooling temperature is significantly influenced by the heat source temperature and heat transfer ability on the source side and is less influenced by the flow rate. Overall, this novel terminal has good thermal performance and is worthy of further optimization.

Energy investigation of glazed windows containing Nano-PCM in different seasons

Incorporating paraffin wax into double glazed windows is a novel method to reduce energy consumption and adjust indoor thermal environment of buildings. However, the low thermal conductivity of paraffin wax limits the thermal performance of glazed windows. Adding nanoparticles into phase change material (PCM) is one of the effective methods to improve thermal performance. In this study, the effect of nanoparticle volume fraction and particle diameter on the temperature difference between the glass interior surface and indoor environment, and energy consumption of glazed windows containing Nano-PCM were numerically investigated for representative days of different seasons. The developed numerical model was validated with the experimental results obtained in this work. The results show that the higher nanoparticle volume fraction, the higher energy consumption, and the larger particle diameter, the smaller energy consumption. The minimal energy consumption is obtained with nanoparticle concentration of 1% and nanoparticle diameter of 100 nm for all the seasons. The magnitude of impact of the studied parameters is more significant in winter. Energy consumption can be reduced up to 4.0% by an appropriate selection of nanoparticle volume fraction and nanoparticle size. The temperature difference between interior surface of glazed windows and indoor environment are mainly concentrated in the range of 1–4 °C for summer, 5–10 °C for autumn and 14–16 °C for winter.

Energy efficiency optimization strategies for university research buildings with hot summer and cold winter climate of China based on the adaptive thermal comfort

Hot summer and cold winter zone is a typical climate region in China with high temperatures and stuffiness in summer and low temperature and moisture in winter. The existing buildings bear of both poor thermal performance of building envelope and poor indoor thermal environment. With the development of social economy, increasing demand towards building indoor thermal environment is much more urgent than before, and hence energy consumption has rapidly risen. Energy efficiency retrofit with low cost has become a priority in this region.Universities and colleges are one of the typical energy consumers in this region, which are insufficient in research. Over all the campus buildings, research building occupies a large part in total campus energy use, and hence becomes the main retrofit objects. Research buildings have complicated functions of offices, scientific research and laboratories, and space heating and cooling behaviors have their own characteristics, which have the large effect on space heating and cooling use. However, there is little knowledge about adaptive thermal comfort and corresponding heating and conditioning energy-use behaviors.In view of this, in this paper, a typical research building located in Hangzhou was chosen and the measurements on indoor thermal environment heating and cooling behaviors, fenestration and energy consumption were carried out during July 2016 to October 2017. By the analysis on field investigation, delivered questionnaires and measured data, the typical space heating and cooling behaviors, fenestration and thermal environment are analyzed. On this base, energy efficiency optimization strategies in terms of building envelope thermal performance, sun shading, and adaptive space heating and cooling behavior are explored by the simulation. The study provides the technic support for energy saving retrofitting of campus buildings in this region.

The Testing Research on Prefabricated Building Indoor Thermal Environment of Earthquake Disaster Region

Prefabricated buildings (PBs) play an important role in the reconstruction process. However, the PBs actual indoor thermal environment located in earthquake disaster region occur deviation because of the result of various factor comprehensive roles, such as the more diverse climate and environmental conditions. According to this situation, field test and questionnaire are carried out under the winter climatic condition of Lushan County, China to explore the actual indoor thermal environment state. Measured and surveyed results show that the average indoor air temperature of the prefabricated classroom and the brick-concrete structure classroom are 10.17 ℃ and 9.29 ℃, respectively. Surface temperature of the prefabricated classroom changes synchronously with the air temperature while its indoor air temperature is little higher. The peak temperature difference of inner and outer surface can be reached to 5.9 ℃ and 5.24 ℃, respectively. Meanwhile, in the case of the overall average clothing thermal resistance of 1.57clo, ASHRAE scales for 0 thermal sensation vote is only 20%, and most people expect that temperature should be higher, which agree with that of the field test analysis. These results reveal that the actual indoor thermal environment inside the measured prefabricated building cannot meet the students’ thermal comfort requirements and sometimes it is also worse than that of brick-concrete classroom, due to low thermal inertia and poor thermal insulation of the in-walled light steel envelope.

A Bicycle-Based Field Measurement System for the Study of Thermal Exposure in Cuyahoga County, Ohio, USA

Collecting a fine scale of microclimate data can help to determine how physical characteristics (e.g., solar radiation, albedo, sky view factor, vegetation) contribute to human exposure to ground and air temperatures. These data also suggest how urban design strategies can reduce the negative impacts of the urban heat island effect. However, urban microclimate measurement poses substantial challenges. For example, data taken at local airports are not representative of the conditions at the neighborhood or district level because of variation in impervious surfaces, vegetation, and waste heat from vehicles and buildings. In addition, fixed weather stations cannot be deployed quickly to capture data from a heat wave. While remote sensing can provide data on land cover and ground surface temperatures, resolution and cost remain significant limitations. This paper describes the design and validation of a mobile measurement bicycle. This bicycle permits movement from space to space within a city to assess the physical and thermal properties of microclimates. The construction of the vehicle builds on investigations of the indoor thermal environment of buildings using thermal comfort carts.

Green and Building Energy Efficiency

According to the greening construction to improve the effect of micro climate,we analyzes several greening measures to the influnence of building thermal environment, and have the conclusion:Greening can greatly improve the building indoor thermal environment, save energy, have the effect to beautify the city and improve the urban ecological environment.

Determining optimum control of double skin envelope for indoor thermal environment based on artificial neural network

This study aims to develop an artificial neural network (ANN)-based temperature control method to keep energy efficient indoor thermal environment in buildings with double skin envelope systems. Control logic that effectively controls the opening conditions of air inlets and outlets of the double skin envelope as well as the operation of the cooling system was developed employing the ANN model. To determine the optimal structure and learning methods for the ANN model, a parametrical optimization process was conducted in terms of the number of hidden layers, the number of neurons in the hidden layers, learning rate, and moment; this process was followed by performance tests of various optimized models. Analysis of the performance tests proved predictability and adaptability of the developed ANN model for diverse background conditions in terms of stable root mean square (RMS) and mean square error (MSE) values. The developed ANN model showed strong potential as a temperature control method for indoor thermal environment of buildings with double skin envelope systems.

A fast-POD model for simulation and control of indoor thermal environment of buildings

Precise and efficient control strategies of heating, ventilation, and air conditioning (HVAC) systems need detailed and dynamic indoor environment information, which is hardly acquired satisfying realtime and precision requirements simultaneously. In this study, a fast simulation method based on existing proper orthogonal decomposition (POD) is proposed for dynamic modelling and control of indoor temperature distributions. To meet the realtime and precision requirements at the same time, an offline-online scheme is applied. In the offline stage, the finite volume method (FVM) is used for spatial and temporal discretizations of the indoor temperature distributions. The obtained ordinary differential equations (ODEs) are further order-reduced by POD (Karhunen-Loève)/Galerkin techniques. Snapshot method is used for the reduced-order basis construction. In the online stage, the model predictive control (MPC) strategy is used for the purpose of reference trajectory tracking, within which the proposed POD model is embedded to realtime estimate spacial temperature variation. Both transient and steady performances of the reduced-order model are compared with those of CFD-based simulation. A boundary control test is finally given, which demonstrates the applicability of the technique.

Indoor Thermal Environment Simulation of Xi'an Residential Building in Summer

Natural ventilation is an important role to improve the residential building indoor thermal environment in summer. This paper use Energy Plus to simulate indoor thermal environment and use CFD to simulate indoor air flow for Xi’an residential building, analysis the influence that different ventilation mode for indoor thermal environment factors. Then with the simulated result of PMV-PPD value to estimate indoor thermal comfort. Proved night ventilation is necessary in residential building in Xi’an and effectiveness to improve indoor thermal comfort.

Numerical Simulation Analysis on Residential Building Indoor Thermal Environment of Intermittent Heating in Lhasa Based on DeST

The aim of this paper is to analyze whether the intermittent heating mode is feasible for residential buildings in Lhasa, the thermal parameters of each palisade structure and the influence law of intermittent heating mode on the indoor thermal environment. In this paper, the DeST energy consumption simulation software that is compiled by Tsinghua University was used to simulate and analyze a residential building in Lhasa city. The results show that: It is completely feasible to carry out intermittent heating in Lhasa area. Considering the indoor temperature reduction should not be too large during intermittent heating break, it is recommended to adopt external insulation. Compared with continuous heating mode, heating open 8 hours and 12 hours a day can save energy 24% and 39% respectively. The results can provide evidences for intermittent heating operating control and energy- saving.

Test on Indoor Thermal Environment of Haidong Region in Qinghai Province China in Winter

Selecting a residence of eastern region of Qinghai province as the research object, the author conducted the test on indoor temperature and relative humidity in winter. Based on the analysis of test data, quantitative assessment was made on residential thermal environment in different passive energy saving measures. The results showed that houses with additional sunspaces or the houses with passive technology can still reach the basic requirement of human thermal comfort even in the absence of heating measures. In the daytime, indoor and outdoor temperature could reach to 21.4 °C. According to the test results, passive energy saving measures should be adopted in house construction in order to adapt to the local climate. This way can effectively improve the local building indoor thermal environment in winter.

Effect of window parameters on indoor thermal environment of buildings

Abstract The paper investigates the effect of size, orientation, glass quality and shading of windows on indoor thermal environment of buildings in a hot arid climate. The study uses a validated mathematical model which simulates the transient thermal behaviour of a building. The results show that the indoor environment does not improve significantly if the window glazing is changed from single to double. The results further show that a south facing window has the largest potential to improve winter and summer indoor comfort and each m 2 area of window can provide winter heating to 2–3 m 2 area of the floor. South facing windows improve thermal indoor comfort in summer also.