Throughout this paper, we reviewed the most popular thermal comfort models and methods of assessing thermal comfort in buildings and vehicular spaces. Most of them are limited to specific steady ...state, thermally homogenous environments and only a few of them address human responses to both non-uniform and transient conditions with a detailed thermo-regulation model. Some of them are defined by a series of international standards which stayed unchanged for more than a decade.
The article proposes a global approach, starting from the physiological reaction of the body in thermal stress conditions and ending with the model implementation. The physiological bases of thermal comfort are presented, followed by the main thermal comfort models and standards and finishing with the current methods of assessing thermal comfort in practice. Within the last part we will focus mainly on thermal manikin experimental studies, and on CFD (computational fluid dynamics) numerical approach, as in our opinion these methods will be mostly considered for future development in this field of research.
•Unglazed transpired solar collectors (UTSC) are evaluated in laboratory conditions.•Two types of hole geometry are compared: new lobed geometry with classical round one.•Lobed geometry introduces ...better heat transfer rate comparing to round perforations.•The innovative perforation geometry leads to 40% increase in thermal efficiency.
Renewable energy represents an attractive solution to fulfil two requirements: indoor air quality and energy efficiency. Passive solar systems are easy to implement and effective in areas with high solar potential. The Unglazed Transpired Solar Collector (UTSC) is made of metal cladding with perforations, installed at several centimetres from a building wall, creating thus a cavity, allowing to preheat the fresh air. Several measurements were performed on an innovative perforated solar wall model. This study is a preliminary approach of an analysis on the importance of the orifice shape of the perforated panel as a heat transfer influencing parameter. Both the fluid dynamics and thermal behaviours were investigated. The more complex dynamics of the lobed flows results in a better heat transfer rate. Changing the geometry of the perforations will increase on one hand the orifice’s perimeter and it would generate complex fluid dynamics, resulting in higher mixing between the primary flow and the ambient and thus a higher efficiency of heat recovery of these devices. The comparison of a conventional UTSC with a new geometry with innovative perforation leads to interesting results, with almost 40% increase in thermal efficiency.
In turbulent flows as in HVAC applications, the fluctuation of air speed can affect the sensation of thermal comfort. This study is a part of a larger experimental and numerical campaign intended to ...evaluate the influence of the turbulence intensity at the inlet of air distribution systems on the local draft sensation and thermal discomfort for different ventilation cases using numerical simulations. For five different imposed values of turbulence intensity (0%, 3%, 10%, 30%, 50%) the local heat loss for different body parts was quantified CFD simulations were performed using a realistic model of human body along with an experimental validation with a humanoid thermal manikin. The CFD model was further exploited for several cases to evaluate the influence of turbulence intensity on the comfort indicators and local heat loss. The recorded velocity, turbulence and temperature fields allowed us to estimate the distributions of DR, PPD and PMV indexes which showed no significant changes, but correlations were found for the imposed turbulence intensity and local heat loss on different body parts, indicating the influence on thermal perception.
The building sector plays an important role in the global climate change mitigation objectives. The reduction of CO2 emissions and energy consumption in the building sector has been intensively ...investigated in the last decades, with solar thermal energy considered to be one of the most promising solutions due to its abundance and accessibility. However, the discontinuity of solar energy has led to the study of thermal energy storage to improve the thermal performance of solar thermal systems. In this review paper, the integration of various types of phase-change materials (PCMs) in transpired solar collectors (TSC) is reviewed and discussed, with an emphasis on heat transfer enhancements, including nanomaterials. Thermal energy storage applied to TSC is studied in terms of design criteria, materials technologies, and its impact on thermal conductivity. This review highlights the potential of nanomaterial technology integration in terms of thermal performance improvements. The utilization of nanomaterials in solar walls holds the potential to significantly enhance their performance. The integration of diverse materials such as graphene, graphite, metal oxides, and carbon nanoparticles can pave the way for improving thermal conductivity.
One of the greatest challenges of humanity is to reach world climate-neutrality by 2050. Using renewable energy and in particular solar energy instead of fossil fuels, falls in this direction. A ...quest for the use of the solar energy as much as possible throughout the year becomes very important in this paradigm. A solution for the use of solar energy during the shading of the solar installation caused by clouds, for example, or even at night, is the use of the phase change materials (PCM). Also, to use the solar equipment as much as possible, the use of cascaded PCM appear as necessity. A transpired solar air collector equipped with cascaded PCM was numerically studied using a validated mathematical model, developed in MATLAB, for one specific autumn day in the temperate climate of Romania. Three different PCM with phase change temperatures of 24 °C (RT24), 26 °C (RT26) and 28 °C (RT28), were used for the PCM cascade. The air, the PCM spheres temperatures and the liquid mass fraction in three different zones of the thermal energy storage, at low, intermediate, and high temperature zones were studied. It is also noticeable the phase shift of each PCM zone, the first to release the heat is the RT28, then the RT26 and finally the RT24. The results showed that cascaded PCM storage could be used for an optimized heating/drying condition allowing to store an amount of energy during the first part of the day that could be released during drying time in the second part of the day. During daytime the LTHES stores thermal energy leading to a maximum decrease of air temperature of 4 °C. During night-time the LTHES released the thermal energy into the outlet air flow leading to a maximum increase of 8.4 °C. Analysing the liquid mass fraction of the PCMs, the results showed that only the RT24 zone is totally melting, with a maximum liquid mass fraction of 1, while the RT28 and RT26 reach a maximum liquid fraction at the centre of the sphere of 0.23 and 0.54, respectively.
Transpired solar collectors (TSC) are one of the most popular solar thermal technologies for building façades. TSC use solar energy to heat the absorber surface, which transmits thermal energy to the ...ambient air. A variant of TSC, namely, a double skin transpired solar collector (DSTSC), has been analyzed in this paper, thus providing guide values and a technical point of view for engineers, architects, and constructors when designing such transpired solar collectors. Three important parameters were addressed in this study through numerical simulation: the influence of a separation plate introduced in a TSC, turning it into a DSTSC; the air layer thickness influence on the performance of the collector; and the influence of the used absorber materials for the separation plate material. Greater heat exchange efficiency was noticed for the DSTSC at every imposed airflow rate compared with the TSC. Regarding the thickness of the collector, the efficiency gradually increased when increasing the solar collector thickness until it reached a value of 20 cm, though not varying significantly at a thickness of 30 cm.
In this paper data regarding the utilization of aerogel as a promising material for thermal insulation of the residential and commercial buildings are presented. Also, research work and developments ...in synthesis, properties and characterization of silica aerogels will be addressed. Aerogel is a synthetic porous ultralight material derived from a gel in which the liquid component of the gel has been replaced with a gas. The result is a solid with extremely low density and low thermal conductivity. Sol-gel is the most used method of preparation. Aerogel melts at 1200ºC and the thermal conductivity is almost 0. Is a solid material with the smallest density because contains about 99.8% air. This material has almost unlimited potential, believing that they might find application in most human activities and areas. Aerogel insulation is a good choice because nearly neutralizes all three methods of heat transfer: convection, conduction and radiation. The resistance to convective transfer is given by the fact that air does not circulate in the material structure. The resistance to thermal transfer by conduction is given by the majority of gaseous components. If using a carbon based gel, a high resistance to radiation transfer is obtained. Therefore, the most used aerogel for thermal insulation is the silica aerogel with carbon as nanostructured material. The high price makes it currently inaccessible and less used material. But, inevitably, the aerogel will quickly become one of the most attractive materials in the future.
Solar air collectors are increasingly used nowadays due to their important potential in reducing the energy consumption of buildings. In this context, glazed transpired solar collectors (GTCs) ...represent an interesting solution, but this type of solar air collector is less studied. Consequently, the objective of this work is to thoroughly assess the performance of a GTC prototype under real long-term climatic conditions. First, the design of the GTC is optimized based on methodically experimental tests. The results show that the GTC configuration with a 30 mm air gap among the absorber and the glazing leads to improved heat transfer efficiency and superior global effectiveness, regardless of airflow rates through the solar air collector. This optimized GTC configuration is further studied by integration within the façade of a full-scale experimental building (container-type, light structure). Comparative experimental studies are then carried out concerning the heating energy consumption and ventilation load of the experimental building without/with GTC implemented in the ventilation system, under Bucharest real weather conditions. The data achieved indicate that the GTC prototype is capable of substantially reducing the ventilation load: up to 25% for low solar radiation (below 200 W/m2) and over 50% (achieving even 90%) for moderate solar radiation (between 250 and 380 W/m2). Finally, for high solar radiation (over 400 W/m2), the GTC outlet air temperature exceeds the interior temperature set-point (22 °C) of the experimental building.
In the short and medium term, it is estimated that electric mobility will play an important role in greenhouse gas emissions reduction strategy. However, vehicles with electric propulsion system come ...with a new series of challenges, some of them affecting more or less the well-being of vehicle users. The purpose of this article is to present in an exhaustive manner a review of data existing in the technical and scientific literature regarding thermal comfort of the passengers in the vehicular ambient, with a perspective on specific issues related to the design of the Electric Vehicles. Firstly, a general outline about the subject area is presented and the aspects of the vehicular environment are discussed. Next, a short introduction in the theories of the human thermal comfort, presenting the physiological bases of thermal comfort and a short discussion of the aspects of the vehicular spaces. The standards currently in use for thermal comfort assessment in vehicles are also discussed in the context of their suitability along other experimental methods for research and development. We will discuss in the final part of the article the particularities of Electric Vehicles and some solutions that are worth to be considered. Compared with buildings indoor environment, the vehicle cabin ambient is very different in terms of thermal comfort parameters magnitude and weight and also due to highly transient condition. The present vehicle standards for thermal comfort are constructed based on the building services standards. In regard to all the aspects presented in the present review, the main conclusion of this article is related to the need to develop specific methods for assessing the thermal comfort, solely for vehicles.
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•Literature review on 105 publications — thermal comfort of the vehicle passengers.•Current vehicle thermal comfort standards are based on the building standards.•Need to develop specific methods for assessing the thermal comfort for vehicles.•A thermal sensitivity test device was built to perform tests for humans.•Perspective on specific issues related to the design of the Electric Vehicles.
Urban pollution represents an increasing risk to residents of urban regions, particularly in large, over-industrialized cities knowing that the traffic is responsible for more than 25% of air gaseous ...pollutants and dust particles. Air quality modelling plays an important role in addressing air pollution control and management approaches by providing guidelines for better and more efficient air quality forecasting, along with smart monitoring sensor networks. The advances in technology regarding simulations, forecasting and monitoring are part of the new smart cities which offers a healthy environment for their occupants.
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