High Level Of Thermal Comfort Research Articles

Experimental Study of Indoor Air Distribution and Thermal Environment in a Ceiling Cooling Room with Mixing Ventilation, Underfloor Air Distribution and Stratum Ventilation

A ceiling cooling system integrated with a mechanical ventilation system has been widely used in modern buildings with large sensible cooling loads due to the high thermal comfort level and large energy efficiency. However, there is a lack of systematic research on the influence factors such as ceiling surface temperature and cooling load on the indoor air distribution and thermal environment, and the impact of ventilation system type in the ceiling cooling room is still unclear. Therefore, this paper presented an experimental study of indoor air distribution and thermal environment in a ceiling cooling (CC) room with mixing ventilation (MV), underfloor air distribution (UFAD) and stratum ventilation (SV); the ceiling surface temperature was 17 °C–26 °C and the internal or external cooling load was 41.5 W/m2–69.5 W/m2. The results showed that the vertical air temperature difference and contaminant removal effectiveness were 0.2 °C–0.4 °C and 0.53–0.85 with CC + MV, 0 °C–1.2 °C and 0.68–1.25 with CC + UFAD and 0.3 °C–0.9 °C and 0.50–0.83 with CC + SV, and the corresponding heat removal effectiveness and air diffusion performance index were 0.96–1.11 and 96–100%, 0.9–1.5 and 57–100% and 1.11–1.34 and 71–100%, respectively. Moreover, the difference between mean radiant temperature and air temperature and the predicted mean vote of thermal sensation were from 0 °C to 0.9 °C and between 0 and 0.26 with CC + MV, from −0.1 °C to 2.2 °C and between −0.1 and 0.42 with CC + UFAD and from −0.1 °C to 0.9 °C and between −0.2 and 0.13 with CC + SV. Hence, the ventilation system type clearly affected the indoor air distribution and thermal environment in the ceiling cooling room, and the experimental results would be beneficial for the design and control of a ceiling cooling system combined with a mechanical ventilation system in practice.

Field studies on the energy consumption and thermal comfort of a nZEB using radiant ceiling panel and open-loop groundwater heat pump system in a cold region

Field studies were conducted in an office building in a cold region equipped with a radiant ceiling panel (RCP) and open-loop groundwater heat pump (GWHP) system. First, the indoor thermal comfort in a target office was evaluated based on the results obtained from the physical measurements and survey questionnaire. The results showed that the suspended RCP system could achieve comfortable indoor thermal conditions throughout the year. The indoor temperature was maintained within the range of 22–26 °C, the humidity was within 30–60%, and CO2 concentration was mostly below 1000 ppm. Second, the energy performance was tested simultaneously, and intermittent and continuous operation methods were compared. Under the continuous operation method, a stable indoor environment was maintained, and the COP of the GWHP system increased by 10%. The results showed the potential to further reduce energy consumption and maintain a high level of thermal comfort through the optimization of system operations. Finally, the annual energy consumption was calculated based on the recorded measurements. The results illustrate that this building can reach the ZEB-ready level in Japan. The primary energy consumption can be decreased by approximately 67% compared to the reference by applying the combined system.

Analysis of temperature preference of guests from various countries/regions during summer and winter in a budget hotel in Kyoto, Japan

Energy consumption by air conditioning in hotels is significant and continues to be an important topic in the building energy sector, although hotels do require a high level of thermal comfort. This study focuses on the temperatures that people prefer in Japanese hotels after traveling long distances across countries or regions. We measured room temperature and surveyed 299 Japanese guests, and measured room temperatures on 7,435 nights by Japanese and foreigners. We investigated the transient responses when guests entered a room while resting, sleeping, and waking. Zero heating and cooling costs were directly paid by guests, who were allowed to freely set their preferred temperature. Five interesting findings have emerged from this study. First, there were no significant differences in the temperatures preferred in hotel guest rooms by the Japanese respondents who lived in different regions. Second, Japanese respondents preferred a “cool” environment in summer and a “warm” environment in winter. Third, Japanese respondents tended to prefer “dry” to “moist” in both summer and winter. Fourth, the preferred temperatures differed between summer and winter. Fifth, the preferred temperatures in the same hotel varied depending on the country or region of origin of the respondent, and were not necessarily higher in summer than in winter.

Development of an integrated index to quantify thermal comfort and walkability in urban areas

Although outdoor thermal comfort is extensively investigated in urban areas, the measures are barely focused to determine the walkability through these spaces. Therefore, a space with a high level of thermal comfort can experience a low level of pedestrian agglomeration while a space with a low level of thermal comfort can be massively used by inhabitants. Therefore, the solution to urban design and planning can be significantly altered if both dimensions are simultaneously taken into the account. This study investigates the relationship between spatial configuration and thermal comfort potential to evaluate the effect of spatial configuration on outdoor environmental quality. For this purpose, a framework is developed to understand the impact of built urban areas on thermal comfort and space syntax performance using a high-resolution spatial model to simulate the correlation of thermal comfort and betweenness centrality of a case study neighbourhood in the hot and humid climate area of Al-Khobar in Saudi Arabia. The mixed-use neighbourhood is analysed by the universal thermal comfort index and several space syntax metrics. The presented study uses Grasshopper environment and Ladybug and Decoding Spaces tools. The simulation study expressed that significant changes in orientation and buildings heights have a remarkable effect on improving OTC and space syntax in the urban neighbourhood.

BioZero—Designing Nature-Inspired Net-Zero Building

This article introduces BioZero, a nature-inspired near-zero building proposed for Quay St, Brooklyn, New York. The building is designed for the maximum use of daylight and natural ventilation. This is the result of its shallow plan depth and the inner light wells/ventilation stacks, which also serve the inner circulation space. The light wells/ventilation stacks are created as a result of the organic shape of the internal partitions. The building is constructed from a steel frame and hemp-lime bio-composite material (hempcrete), which smooths out the fluctuations of internal air temperature and relative humidity. The south facing façade is fitted with the Cadmium Telluride (CdTe) photovoltaic array that covers 90% of the opaque surface area of the façade. The design was based on nature-inspired computation, with sustainability principles as guiding constraints. The main findings are that the building achieves −227 tonnes of negative embodied carbon due to sequestration of CO2 in the hemp plant from which the material was harvested, and a net-zero operation. The main conclusions are that in the context of climate emergency, nature inspired design leads to energy efficient buildings with a high level of thermal comfort, which are buildable and sustainable.

Implementation of model predictive control in a large-sized, low-energy office building

Modern and energy-optimized buildings often lack an intelligent and advanced control strategy. Instead, conventional rule-based control (RBC) strategies are still mainly used today, which do not exploit the full performance potential of these buildings. Model predictive control (MPC) has proven in simulation studies and pilot cases to be a promising approach to reduce the energy consumption of buildings, while improving occupants’ comfort. However, there is still a lack of implementing MPC in real, large-scale and fully occupied buildings, to further prove this potential in real building operations. This paper describes the implementation and operation of MPC in a large-sized, low-energy office building. The MPC controller was implemented in a section of the building during a three-month test period from February to April 2020, controlling the supply temperature of heating circuits for thermally activated building systems (TABS). Its performance was compared to the default rule-based control which is active in the other building sections. This allows for a detailed evaluation of MPC versus RBC under identical environmental and operational conditions. The MPC controlled building section used 30% less heating energy than RBC controlled building sections, while the existing high level of thermal comfort could be maintained. Especially in transition periods (i. e. interseasonal periods like late winter/early spring) , the MPC is superior to the conventional heating-curve based control strategy, with heating energy savings of 75%.

RETROFIT ENERGÉTICO EM UM EDIFÍCIO HISTÓRICO EM PELOTAS, RS, SEGUNDO O RTQ-C E A ENERPHIT

A cidade de Pelotas possui 1.700 prédios inventariados pelo município, tendo no seu centro um grande acervo de prédios históricos. É de suma importância criar mecanismos de incentivo para evitar degradamento por abandono. Um desses mecanismos é o retrofit energético, pois além de revitalizar a edificação, também melhora o nível de conforto térmico de seus usuários. Este estudo teve como objeto o retrofit em uma edificação histórica comercial do séc. XIX de Pelotas, RS. Para comparar o desempenho energético da edificação antes e após o retrofit, foram adotados como parâmetros o RTQ-C (Requisitos técnicos para o nível de eficiência energética de edificações comerciais, de serviços e públicas) e a certificação alemã EnerPHit Standard. As simulações computacionais foram realizadas com o software EnergyPlus, observando possíveis medidas de otimização do nível de desempenho da edificação de modo a preservar a fachada e a volumetria do edifício. Em seguida, avaliou-se o custo destas modificações e o tempo de retorno do investimento. Por fim, contatou-se que é possível realizar o retrofit energético em um edifício histórico sem alterar os elementos arquitetônicos de sua fachada obtendo níveis elevados de eficiência energética e conforto térmico. Palavras-chave: Desempenho termoenergético, Patrimônio histórico, Revitalização da edificação.

Cooling Capacity and Energy Performance of Open-Type Ceiling Radiant Cooling Panel System with Air Circulators

Ceiling radiant cooling panel (CRCP) systems are being increasingly applied to commercial buildings due to their high thermal comfort level and energy efficiency. It is recommended that CRCP systems should be operated at a relatively high chilled water temperature to prevent condensation and save energy. However, even though a high chilled water temperature is effective for achieving condensation-free operation and high chiller efficiency, it can lead to insufficient cooling capacity. In this study, a method of enhancing the cooling capacity of CRCP systems was investigated through mock-up chamber tests. The open-type installation of CRCPs and the combination of air circulators were used to enhance the cooling capacity and energy performance of CRCP systems. Experimental results showed that compared to a conventional CRCP system, the cooling capacity of an open-type CRCP system with air circulators increased by up to 26.2%, and its cooling energy consumption decreased by up to 26.4%. Additionally, the open-type CRCP system with air circulators reduced the difference between the room air temperature and mean chilled water temperature. Thus, the proposed system can operate at a relatively high chilled water temperature, which is effective for reducing condensation risk and cooling energy consumption.

Impact Resistance and Comfort Properties of Textile Structures for Sportswear

Protective padding is commonly used in many sporting activities to prevent impact related injuries. In rugby, shoulder pads absorb and disperse the force and energy of an impact with a playing surface or another player. Although the majority of the commercial shoulder pads currently available can reduce the impact force during a front-on tackle, they provide limited amount of thermal comfort to the wearer. In this research, flexible textile structures were designed and investigated for their potential to effectively dissipate the force of impact over a wider area, thus reducing the risk of injury. The impact resistance of these textile structures placed over a body simulant was compared against commercial foam pads using a’ drop test’ method. The results indicated that all the flexible textile structures reduced the impact force. Although their protection level was not as high as the commercial foam, the textile structures showed a higher level of thermal comfort as measured by air permeability, thermal resistance and water vapor resistance. The results were analyzed using oneway ANOVA followed by post-hoc analysis using IBM SPSS software. The Post-hoc analysis showed a significant difference among the test results of various fabrics for impact absorption, air permeability, thermal resistance and water vapor resistance, which are also discussed in this paper.

Control trajectory optimisation and optimal control of an electric vehicle HVAC system for favourable efficiency and thermal comfort

In order to increase the driving range of battery electric vehicles, while maintaining a high level of thermal comfort inside the passenger cabin, it is necessary to design an energy management system which optimally synthesizes multiple control actions of heating, ventilation and air-conditioning (HVAC) system. To gain an insight into optimal control actions and set a control benchmark, the paper first proposes an algorithm of dynamic programming (DP)-based optimisation of HVAC control variables, which minimises the conflicting criteria of passenger thermal comfort and HVAC efficiency. Next, a hierarchical structure of thermal comfort control system is proposed, which consists of optimised low-level feedback controllers, optimisation-based control allocation algorithm that sets references for the low-level controllers, and a superimposed cabin temperature controller that commands the cooling capacity to the allocation algorithm. Finally, the overall control system is verified by simulation for cool-down scenario, and the simulation results are compared with the DP benchmark. The results show that the control system behaviour can approach the DP benchmark if the superimposed controller bandwidth is tuned along with the allocation cost function weighting coefficients, where a fast controller tuning relates to better thermal comfort while a slow tuning results in improved efficiency.

A Systematic Content Review of Artificial Intelligence and the Internet of Things Applications in Smart Home

This article reviewed the state-of-the-art applications of the Internet of things (IoT) technology applied in homes for making them smart, automated, and digitalized in many respects. The literature presented various applications, systems, or methods and reported the results of using IoT, artificial intelligence (AI), and geographic information system (GIS) at homes. Because the technology has been advancing and users are experiencing IoT boom for smart built environment applications, especially smart homes and smart energy systems, it is necessary to identify the gaps, relation between current methods, and provide a coherent instruction of the whole process of designing smart homes. This article reviewed relevant papers within databases, such as Scopus, including journal papers published in between 2010 and 2019. These papers were then analyzed in terms of bibliography and content to identify more related systems, practices, and contributors. A designed systematic review method was used to identify and select the relevant papers, which were then reviewed for their content by means of coding. The presented systematic critical review focuses on systems developed and technologies used for smart homes. The main question is ”What has been learned from a decade trailing smart system developments in different fields?”. We found that there is a considerable gap in the integration of AI and IoT and the use of geospatial data in smart home development. It was also found that there is a large gap in the literature in terms of limited integrated systems for energy efficiency and aged care system development. This article would enable researchers and professionals to fully understand those gaps in IoT-based environments and suggest ways to fill the gaps while designing smart homes where users have a higher level of thermal comfort while saving energy and greenhouse gas emissions. This article also raised new challenging questions on how IoT and existing developed systems could be improved and be further developed to address other issues of energy saving, which can steer the research direction to full smart systems. This would significantly help to design fully automated assistive systems to improve quality of life and decrease energy consumption.

Effect of adding insulation on the energy performances of rammed earth buildings in hot and arid climates

In a world context focused on energy efficiency and sustainable construction, returning to the use of raw earth in construction constitutes a good alternative to concrete construction, a system more energy consuming and yet more used nowadays. This return is justified by the excellent energy performance and the high level of thermal comfort provided by earth constructions in different climates. In cold climates, adding an insulation on earth walls has proven to be effective in improving their thermal performances. However, the influence of adding an insulation on the energy performance of rammed earth buildings in hot and arid climates remains to this day little explored. The present work comes in this order of ideas; it is based on a comparative study of the energetic performances of a mud building before and after the addition of the insulation. In order to compare between their performances, we have performed a simulation of the thermal behaviour of each by the dynamic thermal simulation software Design Builder.

Multi-objective optimization for designing of high-speed train cabin ventilation system using particle swarm optimization and multi-fidelity Kriging

Maintaining a high level of thermal comfort and indoor air quality for occupants while minimizing the system energy consumption is crucial for the long-haul High-speed train cabins. The traditional way of handling the multi-objective problem relies on the “trial and error” design which involves lengthy manual design parameter adjustment and performance evaluation based on on-site measurements or analytical and empirical models. To shorten design optimization process, a multi-objective optimization platform has been developed using the nondominated sorting-based particle swarm optimization (NSPSO) algorithm for searching the trade-off optimal design of the ventilation system in a fully occupied high-speed train (HST) cabin. A computational model of the HST cabin occupied by four full rows of passengers was constructed using ANSYS Fluent. To ensure the accuracy of the CFD model, high resolution computational thermal manikins were adopted to simulate the thermal and pollutant dispersion under influence of the passengers. Different combinations of ventilation operation parameters were evaluated against its performance in terms of thermal comfort, air quality and energy consumption. Furthermore, to reduce the computational cost of constructing the training sample, a Multi-fidelity Kriging technique is also proposed a surrogate method in replacing the time-consuming CFD simulations while maintaining acceptable accuracy. The result demonstrates that the presented approach is capable to perform a multi-objective optimization for indoor ventilation system design and yield accurate Pareto-front result with up to 35.61% saving of computational time.

Incorporating cooling and ventilation effects into a single IEQ indicator

The influence of dissimilar cooling and ventilation system combinations on indoor environmental quality (IEQ) has been studied. A comparison of chilled ceiling cooling in combination with displacement ventilation, cooling with fan coil unit, and cooling with flat wall displacement inlets was performed. All observed variations were evaluated based on whole-body and local thermal comfort criteria as well as with regard to ventilation effectiveness. The analysis was made based on results of numerical simulations carried out in two steps. First, DesignBuilder was applied to model the buildings’ thermal performance and to evaluate its interaction with the environment. The latter included the calculation of heat gains as well as the heat loss on the boundary surfaces of the observed air-conditioned room. In the second step, ANSYS Fluent was used to simulate the response of indoor environment by utilizing the simulation results obtained in the first step, in order to evaluate the interaction between building and human. Afterwards, the observed thermal comfort and ventilation criteria were merged into a novel indoor environment indicator, which enables to describe the indoor environment quality with a single value. Among the analysed systems, the ceiling cooling system in combination with displacement ventilation was found to be the most suitable as it offers a high level of thermal comfort with adequate ventilation efficiency. Fan coil cooling was the least favourable option in terms of thermal comfort, while flat wall displacement inlets exhibited the lowest ventilation effectiveness. The performed investigation demonstrated the necessity to assess indoor environment with regard to IEQ in addition to energy consumption.

Multi-Objective Optimization of the Envelope of Building with Natural Ventilation

A properly designed house should provide occupants with the high level of thermal comfort at low energy demand. On many occasions investors choose to add additional insulation to the buildings to reduce heat demand. This may lead to overheating of the building without a cooling system in summer periods (these prevail in Poland). Additionally, it affects the deterioration of thermal comfort, which can only be improved by increasing ventilation. The paper presents the multi-objective optimization of the selected design parameters in a single-family building in temperate climate conditions. The influence of four types of windows, their size, building orientation, insulation of external wall, roof and ground floor and infiltration on the life cycle costs and thermal comfort is analyzed for the building without cooling. Infiltration changes during the simulation and is controlled by a special controller. Its task is to imitate the behavior of occupants in changing the supply airflow. Optimal selection of the design parameters is carried out using Non-dominated Sorting Genetic Algorithm II (NSGA-II) by coupling the building performance simulation program EnergyPlus with optimization environment. For the single-family house, optimal values of design variables for three different criteria are presented.

An experimental study of the effect of different starting room temperatures on occupant comfort in Danish summer weather

As office workers will usually have a slightly elevated metabolic rate when arriving at work, they may prefer a room temperature below the comfort range for sedentary activity in the morning. This possibility was studied in an experiment with 25 young people, male and female, exposed to four different conditions. Each condition consisted of two sessions, the simulated commute (activity equivalent to walking to work) and the office session. Each office session had a different starting room temperature, namely 18.5 °C, 20 °C, 21.5 °C or 23 °C, followed by an increasing temperature “ramp” of 1.5K every 30 min. During the last 30 min the temperature remained constant. Physical measurements were continuously recorded and subjective evaluation questionnaires were completed every 30 min. It was observed that, upon arrival at the office-lab, a room temperature of 20 °C provided a thermal environment with neutral thermal sensation (0.23), low thermal dissatisfaction (8.6%) and a high level of thermal comfort for the whole body (3.3). It was concluded that, in the cooling season, to improve the thermal sensation of occupants, a lower temperature than is suggested by the existing standards should be maintained in the early office hours, and that this will lead to a lower maximum room temperature during the day, which would result in less demand for cooling during the summer period.

A parametric building energy simulation case study on the potential and limitations of passive design in the Mediterranean climate of Malta

The present case study sets out to investigate the potential and limitations of passive building design in a typical Mediterranean climate. The Maltese Islands were taken as the case study location. Assuming a fully detached, cuboid-shaped, generic multi-storey office building, one representative storey was modelled by means of the building energy simulation code WUFI®Plus. Thermal comfort was analysed based on the adaptive acceptable operative room temperature concept of EN 15251 for buildings without mechanical cooling systems. Assuming neither artificial heating nor cooling, the free-running operative room temperature was evaluated. By means of a parametric study, the robustness of the concept was analysed and the impact of orientation, window to wall area ratio, glazing, shading, thermal insulation, nighttime ventilation and thermal mass on the achievable level of thermal comfort is shown and discussed. It is concluded that in a well-designed building and by means of decent insulation (present case: Uwall = 0.54 W/(m2 · K)), double glazing, variable external shading devices and passive cooling by nighttime ventilation, a high level of thermal comfort is achievable in this climate using only very minor amounts of energy for artificial heating and cooling or possibly even none at all.

Numerical investigation of roof heating impacts on thermal comfort and air quality in urban canyons

Impacts of thermal and buoyancy forces on the thermal comfort and air quality in urban canyons with different H/W ratios and rise/run ratio of rooftops are studied. 18 isothermal and non-isothermal models are studied by CFD modeling validated with experimental data from the literature. Based on the results, thermal buoyancy is observed to be effective in improving human comfort in the urban canyon. The temperature difference between roof surface and air increases the speed of air and contaminant transport in urban canyons. While the increase in height and tilt of structures around urban areas have shown to reduce thermal buoyancy. In broad canyons such as H/W=0.5, an increase in height and slope of the roof causes the thermal comfort of leeward, windward, and central regions to move away from the neutral comfort conditions. In regular canyons, H/W=1, the thermal comfort reduces for highly slanted roofs models. Domed roof leads to the lack of thermal comfort in upper levels of passages in leeward, windward, and central regions. In deep canyons, H/W=2, high level of thermal comfort appears only for flat roofs. With an increase in roof height (rise/run), Predicted Mean Vote PMV index moves away from the comfort range. By increasing H/W ratio, roof height, wind comfort, and air quality inside regular and deep urban canyons, it was observed that the thermal buoyancy force leads to the reduction in thermal comfort.

An Economic Model-Based Predictive Control to Manage the Users’ Thermal Comfort in a Building

The goal of maintaining users’ thermal comfort conditions in indoor environments may require complex regulation procedures and a proper energy management. This problem is being widely analyzed, since it has a direct effect on users’ productivity. This paper presents an economic model-based predictive control (MPC) whose main strength is the use of the day-ahead price (DAP) in order to predict the energy consumption associated with the heating, ventilation and air conditioning (HVAC). In this way, the control system is able to maintain a high thermal comfort level by optimizing the use of the HVAC system and to reduce, at the same time, the energy consumption associated with it, as much as possible. Later, the performance of the proposed control system is tested through simulations with a non-linear model of a bioclimatic building room. Several simulation scenarios are considered as a test-bed. From the obtained results, it is possible to conclude that the control system has a good behavior in several situations, i.e., it can reach the users’ thermal comfort for the analyzed situations, whereas the HVAC use is adjusted through the DAP; therefore, the energy savings associated with the HVAC is increased.

Multi-objective optimization of HVAC system using NSPSO and Kriging algorithms—A case study

In modern building design, engineers are constantly facing challenging to find an optimal design to maintain a high level of thermal comfort and indoor air quality for occupants while minimizing the system energy consumption. Over the past decades, several algorithms have been proposed and developed for optimizing the heating, ventilation and air conditioning (HVAC) system for indoor environment. Nevertheless, majority of these optimization algorithms are focused on single objective optimization procedures and require large training sample for surrogate modelling. For multi-objective HVAC design problems, previous studies introduced an arbitrary weighting factor to combine all design objectives into one single objective function. The near optimal solutions were however sensitive to the chosen value of the weighting factor. Aiming to develop a multi-objective optimization platform with minimal computational cost, this paper presents a nondominated sorting-based particle swarm optimization (NSPSO) algorithm together with the Kriging method to perform optimization for the HVAC system design of a typical office room. In addition, an adaptive sampling procedure is also proposed to enable the optimization platform to adjust the sampling point and resolution in constructing the training sample. Significant computational cost could be reduced without sacrificing the accuracy of the optimal solution. The proposed methods are applied and assessed in a typical HVAC system and the results indicate that comparing to traditional methods, the presented approach can handle multi-objective optimization in ventilation system with up to 46.6% saving of computational time.