Thermal Comfort Requirements Research Articles

A Survey of the Influence of Air Distribution on Indoor Environment and Building Energy Efficiency

With society paying more and more attention to energy conservation, building energy conservation has become a problem that must be considered in the design phase. In addition, modern life makes people spend more time indoors every day. Reasonable indoor air distribution positively impacts a comfortable indoor thermal environment and reduces building energy consumption. This paper discusses the influence of air distribution on indoor thermal comfort and building energy saving. Reasonable air distribution in the air-conditioned room will create a comfortable indoor thermal environment, which is helpful for the physical and mental health of personnel and efficient work. Meanwhile, it can also effectively reduce the equipment's initial investment and operating energy consumption and realize building energy savings. The design of indoor air distribution cannot be a single, isolated project. A comprehensive analysis based on each station's environmental thermal comfort requirements in the work area must be carried out to reduce air-conditioning operation energy consumption and achieve building energy-saving goals. For existing buildings and large space buildings, the corresponding air distribution design scheme should be designed reasonably. This paper also suggests future research directions on indoor air distribution.

Design and optimization of a baffle-type phase-change heat storage electric heating device

Aiming at the phenomenon of excess power and large peak-valley power difference in various application areas, here we design a baffle-type phase change heat storage electric heating device. The device uses expanded graphite (EG)/paraffin (PA) as the heat storage medium, and encapsulates the EG/PA composite phase change materials (CPCM) in a rectangular slab that is directly heated using an electric heating slab. To investigate the impact of the number and thickness of the rectangular plates on the thermal storage and exothermic performance of the device, we perform three-dimensional numerical simulations. We further make performance comparisons with the commonly used shell-and-tube and concentric tube types. In addition, the designed device was optimized by adding fins using the orthogonal test method. To verify the heating effectiveness of the device, we also simulated the temperature field, PMV (Predicted Mean Vote), and PPD (Predicted Percentage Dissatisfied) of the heating room. Our investigations confirm continuous heat release of the device for 7 h during the day which meets home heating requirements. It is also shown that the heat storage and exothermic efficiency reach to 85.83% and 90.1%, respectively, after the device is optimized, the storage and exothermic efficiency increased by 8.15% and 6.43% respectively, and the real-time outlet temperature has increased by 4.98 °C compared with that before the optimization; the average indoor temperature of the heating room is 22.49 °C, PMV is 0.55, and PPD is 15.3% in line with the thermal comfort requirements. The device can realize heat storage and heating at the same time when the power is in the valley, during the peak period, the power supply is turned off and the heating is directly supplied by CPCM. compared with the direct electric heating systems can reduce users' electricity costs, and shift peaks and fill valleys and provide a broad commercialization prospect. The research results provide a reference for the design and optimization of heat storage devices and their application in practical engineering.

Thermal behavior evaluation of a radiant floor heating system incorporates a microencapsulated phase change material

The rapid growth of urbanization and the increase of internal comfort requirements impact negatively the environment and the energy consumption of the building sector. Therefore, it becomes very crucial to provide an internal thermal comfort with environmentally friendly techniques. In cold regions, the heated floor incorporates a phase change material is an outstanding technique that can ensure high thermal performance and meet the thermal comfort requirements of occupants. In the present study, the thermal performance of a heated floor impregnates a microencapsulated PCM was numerically studied and evaluated. The heated floor system consists of tubes where hot water circulates, buried under the ground made up of different layers. The thermal waves rise from below heat up the ground which in turn transmit the flow recovered. The integration of a PCM in the floor mainly aims to benefit from its considerable storage ability in order to reduce the energy consumption of the heating system and stabilizes internal temperature around the set temperature of comfort in a long time. To evaluate the PCM under-floor heating system a physical model based on two-dimensional computation is used. The calculations are made by considering the enthalpy approach and applying the numerical finite volume method. The effect of different parameters such as microcapsules integration, mass fraction, tubes inter-distance and PCM type on the heated floor thermal performance are evaluated and discussed. The obtained results show that the best performance of the heated floor is got when 15% of microcapsules are placed above the heating tubes. Consequently, an increase of 4 °C in the amplitude and a phase shift of 5 h 30 min compared to the base case (heated floor without PCM) are obtained.

A Review of HVAC System Optimization and Its Effects on Saving Total Energy Utilization of a Building

The paper illustrates the review on the optimizations studies of HVAC systems based on three main methods – HVAC operational variables optimization, optimization of control parameters in HVAC system and parameter optimization in building models. For the HVAC system’s operational variables, the optimization process is based on the common and prescient energy utilization models. Thus, by comparing both, the non-common HVAC system models can get better output of energy reduction. Based on most of the studies, the occupancies thermal comfort requirements, are represented by the indoor air quality (IAQ) or the predicted mean vote (PMV) indexes. Comparing both requirements, the PMV index had a better overall energy reduction output of 47% and estimated annual energy reduction of 2,769 kg/year. Meanwhile, in optimization of HVAC’s control parameters, its overall aim is to achieve a better response output of the HVAC system in order to prevent energy wastage. Among this different optimization’s controller, the fuzzy logic tuning optimization has a better overall energy reduction. On the other hand, the parameter optimization in building model approach is performed before the construction of the structure itself, where multiple construction parameters are considerations in the design. In overall, when different tools for building parameter and model optimization are compared, the EXRETopt by using PMV comfort index approximately reduces 62% of the energy utilization.

Self-healing inorganic hydrated salt gels for personal thermal management in the static and dynamic modes

Thermal comfort is of great significance to maintain the normal metabolism of life. Personal thermal management (PTM) that passively regulates the immediate environment around the human body is a promising alternative. In this work, we report a state-of-the-art concept of self-healing inorganic hydrated salt gels (IHSGs) constructed by ionic crosslinking, covalent crosslinking and hydrogen bond crosslinking for wearable PTM. Sodium sulfate decahydrate (SSD) is selected as the energy storage medium on account of its phase change temperature near the human body temperature. The calcium alginate and the sodium polyacrylate construct the double gel network to anchor the SSD. The dynamic hydrogen bond and the dynamic ionic bond enable the self-healing feature of the SSD IHSGs. The proposed SSD IHSGs with 4% borax, 0.1% sodium hexametaphosphate and 8% sodium polyacrylate demonstrate suppressed phase separation, eliminated supercooling, highly form-stability, high instinct thermal conductivity (0.80 Wm-1K−1), high energy storage capacity (147.14 Jg−1), high self-healing rate (94.3%) and highly cost-effectiveness (energy storage cost 2.44 × 10-3 ¥J−1). Taking advantages of the above merits, the IHSGs are applied in wearable PTM in the static and dynamic modes to meet the thermal comfort requirements. It is anticipated that the one-stop IHSG solution offers great prospect for the advanced wearable PTM.

Janus-Type Hydroxyapatite-Incorporated Kevlar Aerogel@Kevlar Aerogel Supported Phase-Change Material Gel toward Wearable Personal Thermal Management.

Thermal comfort is of great significance to maintain people's healthy state in physics, physiology, and psychology. Personal thermal management (PTM) that passively regulates the immediate environment around the human body has been proposed as a promising strategy to realize on-demand human thermal comfort. In this work, we propose a one-stop solution for the state of the art PTM by combining thermal shielding and thermal energy storage in a Janus-type wearable device, which is named a Janus-type hydroxyapatite-incorporated Kevlar aerogel@Kevlar aerogel supported phase-change material gel (HKA@KPG). The lower HKA with an ultralow thermal conductivity directly attached on the skin can effectively hinder heat transfer from the external environment to human skin. The upper KPG possessing a superior form stability and high energy storage capacity can absorb the heat generated by the human body to regulate the skin temperature. Both the HKA and KPG also demonstrate excellent biocompatibility. Due to its synergistic effect in thermal energy regulation, the Janus HKA@KPG has been applied in wearable PTM in static and dynamic modes to meet the thermal comfort requirements. It is anticipated that the one-stop thermal comfort solution for thermal shielding, thermal energy storage, self-supporting characteristics, wearability, and biosafety offers new possibilities for the next generation of wearable PTMs.

Simulation Investigation of Natural Ventilation on the Thermal Comfort in Arid Regions: Case Ghardaïa

Building aeration ventilation may contribute to achieve thermal comfort there by economizing huge amount of electricity that would be supplied using conventional air conditioning systems. Natural ventilation maintains thermal equilibrium between heating and cooling balances. They may also be used in conjunction with other systems in certain circumstances. Model governing equation of physical phenomena enabling description the thermo-aeraulic behaviour. Based on the measurements in winter and summer periods of several physical parameters like the wind velocity and the ambient temperature, the influence of infiltration rate on the thermal comfort were demonstrated. The present study is the simulation investigation the evolution of internal multi-zone temperature of Saharan building in Ghardaïa (32°38 N, 3°78 E), Algeria. Building construction process should take advantage of many practices characterizing location traditional construction. Specifically, satisfaction of seasonal thermal comfort requirement (heating, cooling) and favour maximum solar passive gains. The results showed that the major factor for the reduction of the internal temperature of the studied building is the natural ventilation including the thermal comfort range (20-27)℃.

A Decentralized Boltzmann-machine-based fault diagnosis method for sensors of Air Handling Units in HVACs

As a key module in a Heating, Ventilation, and Air Conditioning (HVAC) system, an Air Handling Unit (AHU) is controlled based on information collected by sensors to satisfy human thermal comfort and air quality requirements. Fault diagnosis is critical since it allows maintenance crews to know which faults have occurred to improve system availability. However, fault diagnosis in AHUs is challenging because of the following reasons. First, widely used fault indicators are correlated with changing environments, e.g., weather dynamics or occupants, thus may not be enough to distinguish faults. Second, existing decentralized fault diagnosis methods developed for sensors require solving many optimization problems, leading to high computational requirements. To overcome these challenges, this paper develops a decentralized Boltzmann-machine-based method. To address the first issue, residuals between actual values of several sensor readings and their estimates are considered as fault indicators since they are not related to changing environments. To address the second issue, a novel decentralized voting mechanism is developed based on the convergence characteristic of the Boltzmann machine to locate sensor faults while avoiding solving many optimization problems. However, the established Boltzmann machine usually has an asymmetric weight matrix, and thus it does not converge to the state estimates of sensors. To guarantee convergence, a new symmetrization method is developed to symmetrize the Boltzmann machine by adding an extra unit into the Boltzmann machine to reset the weight matrix while retaining the original voting. Experimental results demonstrate that our method can effectively diagnose sensor faults with high diagnostic accuracy.

A Moisture-Wicking Passive Radiative Cooling Hierarchical Metafabric.

Developing functional textiles with a cooling effect is important for personal comfort in human life and activities. Although existing passive cooling fabrics exhibit promising cooling effects, they do not meet the thermal comfort requirements under many practical conditions. Here, we report a nanofiber membrane-based moisture-wicking passive cooling hierarchical metafabric that couples selective optical cooling and wick-evaporation cooling to achieve efficient temperature and moisture management. The hierarchical metafabric showed high sunlight reflectivity (99.16% in the 0.3-0.76 μm wavelength range and 88.60% in the 0.76-2.5 μm wavelength range), selective infrared emissivity (78.13% in the 8-13 μm wavelength range), and good moisture permeability owing to the optical properties of the material and hierarchical morphology design. Cooling performance experiments revealed that covering simulated skin with the hierarchical metafabric prevented overheating by 16.6 °C compared with traditional textiles, including a contribution from management of the humidity (∼8.2 °C). In addition to the personal thermal management ability, the hierarchical metafabric also showed good wearability.

Investigation of thermal comfort performance and optimization of a novel refrigerant-heated radiator

In this study, a novel refrigerant-heated radiator (RHR) was introduced and a computational fluid dynamics (CFD) model was developed to investigate the influence of RHR structure parameters on indoor thermal comfort under heating and cooling conditions. Results show that the heating capacity and thermal comfort are improved with the increase of length-to-height ratio, while the thermal comfort is infringed if the length-to-height ratio is too large in cooling conditions. The length-to-height ratio of the RHR with 2.22–3.71 is recommended to meet the thermal comfort requirements in heating and cooling conditions. Comparisons were made between the RHR and air conditioner on indoor thermal comfort, which indicates that the RHR has a better thermal comfort in heating conditions in terms of temperature field, velocity field and thermal comfort indices. Under cooling conditions, the air conditioner has lower temperature distribution and more uniform vertical temperature distribution in human activity area, while the RHR has the excellent performance in the velocity distribution and thermal comfort indices. The findings show RHR has a better thermal performance than air conditioners in terms of overall thermal comfort. The research provides a guide to the benefit of RHR and improves the thermal comfort of ASHP system.

Recognition and prediction of individual thermal comfort requirement based on local skin temperature

This study focuses on identifying individual thermal comfort requirement using infrared images. The primary objective is to verify the feasibility of infrared images in predicting thermal comfort parameters, and to propose corresponding prediction models for two different classification modes defined in this study. The relevant data for modeling was obtained via chamber experiments. In addition, multiple machine learning (ML) algorithms, such as logistic regression (LR), support vector machines (SVM), and random forest (RF), were applied to propose models in which the local skin temperature (forehead, eye, nose, cheek and ear) measured using the infrared camera is used as an input parameter and thermal sensation vote (TSV) is used as an output parameter. The area under curve (AUC) of each model on the test set was calculated and used as the main evaluation index. In order to compare with the traditional thermal comfort model, the accuracy was also concerned as an evaluation index. The result shows that the prediction accuracy of ML models based on local skin temperature is close to that of predicted mean vote (PMV) model and indicates significant feasibility for practical application. Among the models, the AUC and accuracy of LR model reflects a relative advantage in comparison with other ML models and PMV model. The selection of measurement sites is also discussed in this study, and suggestions for practical application are given according to the performance of the models based on selected algorithms.

Improving Energy Efficiency by Utilizing Wetted Cellulose Pads in Passive Cooling Systems

The effectiveness of using wetted cellulose pads on improving the performance of two conventional passive cooling systems has been evaluated. First, an experimental design was developed to determine the impact of using a wetted cellulose pad on the temperature and velocity of the airflow. A cellulose pad (7090 model) with a cross-sectional area of 0.5 × 0.5 m2 and three different thicknesses of 10, 15, and 30 cm were selected and tested. The results indicated that using wetted cellulose pads with thicknesses ranging from 10–30 cm decreased the outlet airflow temperature from 11.3 to 13.7 °C on average. For free airflow at velocity 3.5 m/s, the outlet airflow velocity from the wetted cellulose pad decreased to 0.9, 0.7 and 0.6 m/s, respectively, for cellulose pads with thicknesses of 10, 15, and 30 cm. By applying experimental results on a psychrometric chart, the humidity ratio of outlet airflow was obtained between 40–70%. The study established airflow velocity as the critical parameter in passive cooling systems. With the novel concept of combining wetted cellulose pads for passive cooling systems (i.e., wind catchers and induced ventilation), there is good potential to reduce the energy requirements for thermal comfort in buildings in regions with a hot and arid climate.

Energy Efficient Thermal Comfort Control for Residential Building Based on Nonlinear EMPC

For purpose of achieving the desired thermal comfort level and reducing the economic cost of maintaining the thermal comfort of green residential building, an energy efficient thermal comfort control strategy based on economic model predictive control (EMPC) for green residential buildings which adopts household heat metering is presented. Firstly, the nonlinear thermal comfort model of heating room is analyzed and obtained. A practical nonlinear thermal comfort prediction model is obtained by using an approximation method. Then, the economic cost function and optimization problem of energy-saving under the necessary thermal comfort requirements are constructed to realize the optimal economic performance of the dynamic process. The energy efficient thermal comfort MPC (EETCMPC) is designed. Finally, the comparison and analysis between EETCMPC and Double-layer Model Predictive Control (DMPC) is simulated. The simulation results reveal that when the clothing insulation is typical, the energy efficiency of EETCMPC is 8.9% and 11.6%, respectively, in the two simulation scenarios. When the clothing insulation varies with temperature, the energy efficiency of EETCMPC is 7.29% and 9.15%, respectively, and the total energy consumption is reduced by about 1.65% and 14.6%, respectively, compared with the typical clothing insulation. The economic performance is improved in the thermal comfort dynamic process of heating room.

Identification of Good Opening Area During the Pandemic Classroom at the Faculty of Engineering Khairun University in Ternate

Good air distribution in the building should provide comfort and health for the wearer. This can be achieved through the design of more specific architectural sections or forms with the aim of maximizing the distribution of cool air. The target of this research is the Faculty of Engineering lecture hall which located on the Khairun Campus and is a new building with 3 floors. For this new normal period, lectures have reached 100 percent of students entering the room, so supporting facilities are needed that meet the requirements of thermal comfort and health protocols. This study aims to analyze good natural ventilation during endemic times in the lecture hall. This rese arch was conducted using quantitative – qualitative descriptive methods in analyzing the data. The results showed that lecture hall have an average temperature of 31.84 °C, with dampness of 68.47 percent and wind speed of 0.12 m/s. Thing This indicates that the thermal conditions in the lecture hall does not meet the standard of thermal comfort has a temperature exceeding 27.1°C, and a dampness level of more than 70 percent and must have a wind speed of 0.2m/s –2m/s. With this condition, the lecture hall has not yet met the standards of good natural good air distribution during the pandemic and has natural air that is not good for health the wearer

Real-time monitoring of occupancy activities and window opening within buildings using an integrated deep learning-based approach for reducing energy demand

Occupancy behaviour in buildings can impact the energy performance and operation of heating, ventilation and air-conditioning (HVAC) systems. HVAC, which uses conventional control strategies or “fixed” setpoint schedules, could not adjust to the conditioned spaces' actual requirements, resulting in building spaces being over or under-conditioned. While the unintended opening of windows can lead to substantial heat loss and consequently raises energy consumption. To optimise building operations, it is necessary to employ solutions such as demand-driven controls, which can monitor the utilisation of indoor spaces and provide the actual thermal comfort requirements of occupants. This study presents a novel vision-based deep learning framework for occupancy activity detection and recognition including the manual window operations in buildings. A region-based Convolutional Neural Network (R-CNN) model was trained and deployed to a camera for real-time detection and recognition. Based on the field experiments conducted within a case study University building, overall accuracy of 85.63% was achieved for occupancy activity detection and 92.20% for window operation detection. Building energy simulation and various scenario-based cases were used to assess the impact of such an approach on the building energy demand and provide insights into how the proposed detection method can enable HVAC systems to respond to dynamic changes within indoor spaces. Results showed that the proposed approach could reduce the over-or under-estimation of occupancy heat gains compared with the use of “fixed” or static profiles. In addition, the approach can help alert building users or managers about windows left open unintentionally, which can reduce unnecessary ventilation heat losses. Furthermore, the approach can also predict the room CO2 concentration and advise occupants about a suitable natural ventilation strategy. The study highlighted the potential of the multi-purpose detection approach, but further development is necessary, including optimisation of the deep learning model, full integration with HVAC controls and further model training and field testing.

Indoor Thermal Comfort in Modern Mosque of Tropical Climate

Purpose The requirement of indoor thermal comfort in building is crucial, including the religious building such as mosque, which accommodates high occupancy level due to the congregational prayer. With this condition, the application of air conditioning system in a mosque is common, especially the modern mosque in hot climate where the layout plan is more complex compared to the vernacular mosque. Hence, the aim of this study is to evaluate whether the modern mosque design is able to provide the required indoor thermal comfort condition in tropical climate. Design/Methodology/Approach The National University of Malaysia’s mosque was selected for the study. Two research methodologies were conducted concurrently, which were the field measurement and the questionnaire survey. The purpose of conducting these two methods was to compare the indoor thermal condition with the actual thermal sensation and satisfaction of the users. Both methods had been executed for four days, and there were 120 respondents who had participated in the survey. Findings The findings indicated that most users felt neutral thermal sensation only during the morning hours which was at the indoor operative temperature range of 28.5 °C to 30.1 °C. Meanwhile in the afternoon and late afternoon hours, where the indoor operative temperature was more than 30 °C, majority of them felt slightly warm. Despite that, they still voted for neutral or satisfied feeling during the afternoon and the late afternoon hours. Research Limitations/Implications The limitations in the study were the field measurement duration which was four days only and the location of the measuring tool which was at the prayer hall of the first floor level. Originality/Value The findings of this study can be used as a guidance in providing a modern mosque design that has good response to the tropical climate. This study also helps to embark other investigations in the future by using other methodologies such as numerical simulation and experiment.

A review of the structure and application of active chilled beams (ACBs) for central air conditioning systems

Active chilled beams (ACBs), as indoor air terminal units in heating, ventilation, and air conditioning (HVAC) systems, have been of great concern in recent years due to the requirements of energy savings and indoor thermal comfort. This paper reviews the structure and application of ACB, which is helpful in identifying current research scenarios and prospects. The results indicate that the structure of ACBs will be improved based on the entrainment ratio (ER), cooling performance and acoustic behavior as the manufacturing level evolves. The mathematical model of ACBs is constantly being optimized, although there is still room for simplification to fit practical applications. Research on airflow patterns and thermal comfort can be extended to larger spaces (including buildings with large sensible heat ratios) and various climates. Based on the optimization of the ACB mathematical model, modern control theory can be focused on the research on ACB control system. ACB system has a coupling trend with other systems to achieve the comprehensive utilization of energy due to the characteristics of high-temperature cooling. In addition, numerous technical issues remain to be resolved to reduce unnecessary energy consumption. These conclusions also provide a simple reference for research and design in the area where this technology is still in its infancy.

Partition control model and application to an electrically heated residential house

With the increasing environmental problems, the problem of high heating energy consumption in residential dwellings in winter is urgent to solve. To fulfill the requirements of energy-saving and thermal comfort simultaneously, this paper proposed different partition heating schemes and simulated their energy consumptions with DeST and TRNSYS. The results indicated that the partition-controlled heating program that preheating 1 h in advance was the most energy-saving, with an energy-saving rate of 14.13%.

Experimental Investigation of Adaptive Thermal Comfort in French Healthcare Buildings

The thermal comfort requirements of disabled people in healthcare buildings are an important research topic that concerns a specific population with medical conditions impacted by the indoor environment. This paper experimentally investigated adaptive thermal comfort in buildings belonging to the Association of Parents of Disabled Children, located in the city of Troyes, France, during the winter season. Thermal comfort was evaluated using subjective measurements and objective physical parameters. The thermal sensations of respondents were determined by questionnaires adapted to their disability. Indoor environmental parameters such as relative humidity, mean radiant temperature, air temperature, and air velocity were measured using a thermal microclimate station during winter in February and March 2020. The main results indicated a strong correlation between operative temperature, predicted mean vote, and adaptive predicted mean vote, with the adaptive temperature estimated at around 21.65 °C. These findings highlighted the need to propose an adaptive thermal comfort strategy. Thus, a new adaptive model of the predicted mean vote was proposed and discussed, with a focus on the relationship between patient sensations and the thermal environment.

Field measurements and numerical analysis on operating modes of a radiant floor heating aided by a warm air system in a large single-zone church

Space heating can constitute 60–80% of the total energy use of buildings in cold climates. Efficient heating techniques in buildings still rely on operating strategies. In this paper, a church with radiant floor heating in a cold climate is taken as a case of a large single-zone building to analyze the energy use for heating. Field measurements and numerical analysis are both used in the study. Different operating modes of heating, including intermittent heating and constant set-point heating, are compared for energy saving, reliability on indoor climate, and thermal comfort. The intermittent heating by an all-air system with supplied air temperature control results in the highest energy use. The constant set-point air temperature radiant floor heating aided by a warm air system (return air temperature control) is least affected by outdoor temperature with the best reliability and met the thermal comfort requirements throughout the heating season. The main novelty is that an operating mode of cyclic set-point air temperature is proposed. It is found that the small thermal inertia of heating systems should be preferred when the operating mode of cyclic set-point temperature is used to reduce the warm-up period. The results suggest how to operate and reduce the energy use of radiant floor heating systems in a large single-zone building.