Personal Thermal Management by Radiative Cooling and Heating

Maintaining thermal comfort within the human body is crucial for optimal health and overall well-being.By merely broadening the setpoint of indoor temperatures,we could significantly slash energy usage in building heating,ventilation,and air-conditioning systems.In recent years,there has been a surge in advancements in personal thermal management(PTM),aiming to regulate heat and moisture transfer within our immediate surroundings,clothing,and skin.The advent of PTM is driven by the rapid development in nano/micro-materials and energy science and engineering.An emerging research area in PTM is personal radiative thermal management(PRTM),which demonstrates immense potential with its high radiative heat transfer efficiency and ease of regulation.However,it is less taken into account in traditional textiles,and there currently lies a gap in our knowledge and understanding of PRTM.In this review,we aim to present a thorough analysis of advanced textile materials and technologies for PRTM.Specifically,we will introduce and discuss the underlying radiation heat transfer mechanisms,fabrication methods of textiles,and various indoor/outdoor applications in light of their different regulation functionalities,including radiative cooling,radiative heating,and dual-mode thermoregulation.Furthermore,we will shine a light on the current hurdles,propose potential strategies,and delve into future technology trends for PRTM with an emphasis on functionalities and applications.

Impact of Varying Blower Opening Degrees on Indoor Environment and Thermal Comfort

At present,air handling units are usually used indoors to improve the indoor environment quality.However,while introducing fresh air to improve air quality,air velocity has a certain impact on the occupants’thermal comfort.Therefore,it is necessary to explore the optimization of air-fluid-body interaction dynamics.In this study,the indoor air flow was changed by changing the opening and closing degree of the blower,and the thermal manikin is introduced to objectively evaluate the human thermal comfort under different air velocities.The main experimental results show that the air change rate increases with the increase of the opening and closing degree of the blower considering an ACH(air changes per hour)range between 3.8 and 10.For a better prediction,a linear correlation with a coefficient of 0.995 is proposed.As the blower’s opening is adjusted to 20%,25%,30%,35%,and 40%,the air velocity sensor positioned directly beneath the air inlet records average velocities of 0.19,0.20,0.21,0.28,and 0.34 m/s over four hours,respectively.Observations on thermal comfort and the average sensation experienced by individuals indicate an initial increase followed by a decline when the blower’s operation begins,with optimal conditions achieved at a 35%opening.These findings offer valuable insights for future indoor air ventilation and heat transfer design strategies.

Research Characteristics of Thermal Comfort of Urban Block Landscape Based on Knowledge Graph Analysis

The landscape environment of urban blocks plays a significant role in improving the comfort of urban thermal environment and promoting green and high-quality development.The 342 papers related to the research on the impact of urban block landscape environment on thermal comfort in China,collected by CNKI(China National Knowledge Infrastructure)from 2002 to 2022,are used as the research object.Through bibliometric statistical analysis,LLR algorithm,and cluster analysis,the current research status of the impact of urban block landscape environment on thermal comfort in China is analyzed and processed,and its external characteristics are identified.Using the information visualization software CiteSpace,the research topics in the field of the impact of urban block landscape environment on thermal comfort are presented in the form of knowledge graphs.Through co-occurrence analysis of keywords and trend of word frequency changes,the development trends of research hotspots and cutting-edge fields of the impact of urban block landscape environment on thermal comfort are determined,hoping to provide reference for future research in this field.

Optimisation of Thermal Comfort of Building in a Hot and Dry Tropical Climate: A Comparative Approach between Compressed Earth/Concrete Block Envelopes

Compressed earth blocks (CEB) are an alternative to cement blocks in the construction of wall masonry. However, the optimal architectural construction methods for adequate thermal comfort for occupants in hot and arid environments are not mastered. This article evaluates the influence of architectural and constructive modes of buildings made of CEB walls and concrete block walls, to optimize and compare their thermal comfort in the hot and dry tropical climate of Ouagadougou, Burkina Faso. Two identical pilot buildings whose envelopes are made of CEB and concrete blocks were monitored for this study. The thermal models of the pilot buildings were implemented in the SketchUp software using an extension of EnergyPlus. The models were empirically validated after calibration against measured thermal data from the buildings. The models were used to do a parametric analysis for optimization of the thermal performances by simulating plaster coatings on the exterior of walls, airtight openings and natural ventilation depending on external weather conditions. The results show that the CEB building displays 7016 hours of discomfort, equivalent to 80.1% of the time, and the concrete building displays 6948 hours of discomfort, equivalent to 79.3% of the time. The optimization by modifications reduced the discomfort to 2918 and 3125 hours respectively;i.e. equivalent to only 33.3% for the CEB building and 35.7% for the concrete building. More study should evaluate thermal optimizations in buildings in real time of usage such as residential buildings commonly used by the local middle class. The use of CEB as a construction material and passive means of improving thermal comfort is a suitable ecological and economical option to replace cementitious material.

Impact of Street Built Environment on Human Thermal Comfort in Summer

With the continuous intensification of the global greenhouse effect,thermal comfort has become a highly concerned issue in the living environment.The study explores the influencing factors and improvement strategies of urban street thermal comfort.The urban heat island effect,environmental parameters,building layout,and green planting all have a significant impact on the thermal comfort of streets.Improvement strategies include optimizing cultivating pattern of plants,adjusting street layout,and improving paving materials of road.The multi-layer vegetation structure provides green shade,reduces local temperature,and humidifies the surrounding environment.It should adjust the street orientation and aspect ratio to provide sunlight and ventilation,and reduce ambient temperature.Paving materials with low reflectivity and light color and permeable underlying surface should be chosen to reduce heat absorption,increase shading and greenery,and improve thermal comfort.

Hygrothermal Study of a House Made of Local Biosourced Materials Based on Clay: Experimental Study

The purpose of this study is to experimentally analyze the thermal behavior of the walls of a prototype experimental house. A Datalogger and thermocouples were used on the experimental house to determine the temperatures of the exterior and interior walls. Also, “MSR” type HygroPuce was used to determine the exterior and interior temperatures and relative humidity of the habitat. The results show that a wall made of bio-based materials with a mixture of “earth + Hibiscus cannabinus L. fibers” allows reducing the fluctuations of the interior temperatures. We observe the peaks of temperatures on the external walls at 11:00 am and for the interior walls, the peaks are observed at 5:00 pm. The maximum thermal phase shift between the peaks of the external and internal temperatures is about 7.5 hours, and the maximum damping factor is 0.9. Also, we note that the thermal performance of the material used in the design of the envelope of the house is determined by the improvement of the response of the envelope in front of the external thermal solicitations.

Low-Cost Insulation for Energy Efficient Buildings in Terai Region of Nepal

There is a huge amount of energy savings potential in public building sector that has yet to be realized.By prioritizing energy efficiency in its own buildings and thus promoting the development of required knowledge in terms of new technology and construction methods,the public sector will lead the way in efforts to increase the rate of renovations.The low-cost insulation strategies and a comparison of cost with existing insulation materials has been described in this study.We have repeatedly faced energy crises and will continue to do so in the future if appropriate action is not taken in a timely manner.Properly implementing energy-saving initiatives in for achieving thermal comfort in buildings as well as reducing the energy costs would undoubtedly inspire the residential sector,resulting in significant reductions in energy usage.Simulations were carried out to study insulation layers on various building components like exterior walls,floor and roofs,generating different scenarios for a building as a base model,which were then compared and analysed to verify the literature used to develop the cases.The proposed recommendations,which have been validated,are certain to increase building energy efficiency,achieve thermal comfort in low cost than what is currently being used.

Experimental Study on Occupant's Thermal Responses under the Non-uniform Conditions in Vehicle Cabin during the Heating Period

The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct to the thermal comfort or thermal sensation of occupants, even to the relationship between thermal conditions and thermal sensation. In this paper, a series of experiments were designed and conducted for understanding the non-uniform conditions and the occupant＇s thermal responses in vehicle cabin during the heating period. To accurately assess the transient temperature distribution in cabin in common daily condition, the air temperature at a number of positions is measured in a full size vehicle cabin under natural winter environment in South China by using a discrete thermocouples network. The occupant body is divided into nine segments, the skin temperature at each segment and the occupant＇s local thermal sensation at the head, body, upper limb and lower limb are monitored continuously. The skin temperature is observed by using a discrete thermocouples network, and the local thermal sensation is evaluated by using a seven-point thermal comfort survey questionnaire proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc（ASHRAE） Standard. The relationship between the skin temperature and the thermal sensation is discussed and regressed by statistics method. The results show that the interior air temperature is highly non-uniform over the vehicle cabin. The locations where the occupants sit have a significant effect on the occupant＇s thermal responses, including the skin temperature and the thermal sensation. The skin temperaWa-e and thermal sensation are quite different between body segments due to the effect of non-uniform conditions, clothing resistance, and the human thermal regulating system. A quantitative relationship between the thermal sensation and the skin temperature at each body segment of occupant in real life traffic is presented. The investigation result indicates that the skin temperature is a robust index to evaluate the thermal sensation. Applying the skin temperature to designing and controlling parameters of the heating, ventilation and air conditioning（HVAC） system may benefit the thermal comfort and reducing energy consumption.

Effects of urban street trees on human thermal comfort and physiological indices: a case study in Changchun city, China

Planting trees along urban streets is one of the most important strategies to improve the urban thermal environment.However,the net impacts of urban street trees on human thermal comfort and physiological parameters are still less clear.On three similar east-west orientated streets with different degrees of tree cover-low(13%),medium(35%),and high(75%),urban microclimatic parameters and human physiological indices for six male students were simultaneously measured on three cloudless days in summer 2018.The results show that the differences in tree cover were predominant in influencing urban thermal environment and comfort.The street with the highest tree cover had significantly lower physiological equivalent temperature(PET) and more comfortable than the other two streets.The frequency of strong heat stress(PET> 35℃) was 64%,11 %,and 0%,respectively,for streets with low,medium,and high tree cover.For the six male university students,human physiological indices varied greatly across the three streets with different tree cover.Systolic blood pressure,diastolic blood pressure,and pulse rate increased with decreasing tree cover.The results also suggest that urban thermal environment and comfort had considerable impact on human physiological parameters.Our study provides reasons for urban planners to plant trees along streets to improve the thermal environment and promote urban sustainability.

An analysis on spatial variation of urban human thermal comfort in Hangzhou, China

Urban human thermal comfort(UHTC) is affected for interacting of weather condition and underlying surface framework of urban area. Urban underlying surface temperature value and Normalized Difference Vegetation Index(NDVI) were calculated using image interpreting and supervised classification technique by ERDAS IMAGE software using 1991 and 1999 Landsat TM images data. Reference to the relational standard of assessing human thermal comfort and other meteorology data of Hangzhou City in summer, air temperature and relative humidity variation of different land types of underlying surface were inversed. By choosing discomfort index as an indictor, the spatial distribution characteristic and the spatial variation degree of UHTC were estimated and mapped on a middle scale, that is, in six districts of Hangzhou. The main characteristics of UHTC spatial variation from 1991 to 1999 were revealed using a GIS-based calculation model. The variation mechanism were analyzed and discussed from the viewpoint of city planning, construction and environmental protection.

Quantitative Analysis of the Outdoor Thermal Comfort in the Hot and Humid Summertime of Shenzhen, China

Outdoor thermal comfort has always been a major issue due to its irreplaceable role in maintaining good health and energy use. Thus,quantitative analysis of outdoor thermal comfort and discussions on influential factors seem very necessary to achieve the climate-conscious urban design. Therefore,an outdoor thermal comfort questionnaire survey and the simultaneous field measurement were conducted in six different places during the hot and humid summertime in Shenzhen. The results show that the overall weather conditions during the investigation can be expressed with high temperature and high humidity with strong solar radiation. The micro-meteorological parameters of six test sites vary greatly due to their different regional spatial layouts.Moderate range of air temperature( Ta) is between 28 to 30 ℃ while that of relative humidity( RH) mainly concentrates in 60%-70% with the thermal sensation votes. The main influential factors impacting outdoor thermal comfort are obtained and Tahas the greatest effect. The overall thermal comfortable ranges in Shenzhen are expressed by the range of 28. 14-32. 83 ℃ of PET and 24. 74-30. 45 ℃ of SET*. With the correlation analysis between the characteristic parameters of regional spatial layout and thermal climate and thermal comfort,it reveals that increasing the coverage ratio of water and green space( S) helps lower Taand increase RH. The global solar radiation( G) has a significant negative correlation with the height of buildings( H) and a positive correlation with sky view factor( SVF). Overall,reasonable configuration of the regional spatial layout contributes to providing a thermal comfortable environment.

Thermal comfort evaluation of people in subway station

We analyzed the characteristics of subway station environment and the change of thermal comfort for passengers when they are in and out of the station. The dynamic thermal comfort evaluation model RWI(relative warmth index) and HDR(heat deficit rate) were built on the distinguishing features of public area in subway station. Taking one representative subway station in Nanjing as the research object, the thermal comfort conditions in different seasons and different parts were studied by field tests, questionnaires and model-evaluating. The calculated RWI shows that although the thermal comfort in Nanjing metro is relatively acceptable, ideal thermal comfort has not been achieved. And it is found that associated with predicted mean vote(PMV), using RWI can evaluate the thermal comfort more precisely.

Research on the Winter Thermal Comfort of Library's Atrium Reading Space in Harbin Universities

As a transition space,atrium not only organizes traffic,makes the flow line flexible,but also modulates the indoor micro-climate. Because of its good sense of space and lighting performance,designers generally set reading space around the atrium. But nowadays,people are more concerned with the external form of the architecture,rather than the thermal comfort conditions of the atrium reading space. This article chooses the universities' library atrium space of Harbin in typical city in cold regions as the carrier of research,testes the thermal environment of atrium reading space, analyzes the user 's subjective feelings of the thermal environment and establishes climate adaptation model applied to library buildings. This paper aims to study on Winter thermal comfort of universities' library atrium reading space in cold area. Bases on thermal comfort adaptive model,it establishes a reasonable heating methods and design temperature index of indoor thermal environment. Optimum comfort is obtained while achieving building energy efficiency and providing viewers a comfortable reading space.

Design of Rural Residence Based on Thermal Comfort: A Case Study of Chengdu Area

With the improvement of living standards, peasants have attached increasing attention to quality of living environment, indoor thermal comfort of rural residence has become a functional need of new countryside residence. Chengdu is a foggy area with shorter sunshine hours, humid air, more foggy but fewer windy days, so local residence is likely to be muggy, which influences comfort of residents seriously. According to relevant researches, most rural residences in Chengdu use only natural ventilation, and the indoor thermal comfort is poor. In view of this, this paper tried to improve indoor thermal comfort and quality of living environment from the perspective of residence functional design.

Layout Optimization of Riverside Residential Area Based on Thermal Comfort: A Case Study of Nanhua Village, Shenzhen

Based on the previous researches on building layout with thermal comfort, this paper Stud Shenzhen Nanhua Village to explore the way of using building layout to change thermal environment of riverfront residential areas. The results showed that a more comfortable outdoor thermal environment could be obtained by applying proper building layouts favorable for the thermal comfort of the Nanhua Village. It proves again that efficient and feasible building layout, which is suitable for a river microclimate, is important in improving thermal comfort of a riverside residential area. The study also provides a good example for the future architectural designs of a riverside residential area for obtaining thermal comfort.

Thermal Comfort Measurement and Landscape Reconstruction Strategy of Street Space Based on Decomposition Grid Method:A Case Study of Yangmeizhu Street

As an important public space in the city,street space is the second residence of people.Taking Yangmeizhu Street as the research object,this study established a street microclimate model in Beijing through microclimate measurement and simulation,and then calculated thermal comfort index of the street and evaluated thermal comfort of the street space and distribution model.The evaluation method used grid method to decompose and study and made several 10m×10m grids for inner space of the street,so as to compare deeply difference of microclimate environment in the street and analyze quantitatively relevance between street space elements(street pavement,street greening,building shadow coverage)and thermal comfort(physiological equivalent temperature PET)in the data.Finally,adaptive strategy of microclimate on street level was put forward to improve the environmental quality of public space in the old city by means of landscape design,aiming at creating a resilient and humanized street space and improving adaptability of microclimate and thermal comfort for living.

Thermal and Moisture Comfort Properties of Down Jacket Fabrics

In order to study the thermal and moisture comfort properties of down jacket fabrics,20 popular down jacket fabrics were selected from the market.The basic specifications of the samples were tested,and thermal and moisture performance tests were conducted.The obtained thermal and moisture indicators were analyzed,and then combined with the subjective evaluation results to obtain the regression equation for the evaluation of the comprehensive thermal and moisture comfort of down jacket fabrics.The air permeability,the thermal resistance,the warm and cold feeling and the moisture permeability were tested,and the results were divided into 5 levels.The results showed that the consistency of the air permeability and the moisture permeability of down jacket fabrics studied was better,and the thermal insulation of the down jacket fabrics with coating was better.The thickness of the down jacket fabrics had an effect on the warm and cold feeling of instant contact,and the consistency of subjective and objective warm and cold feeling was better.The obtained comprehensive evaluation equation of the thermal and moisture comfort has certain guiding significance for the thermal and moisture comfort of down jacket fabrics.

Energy Efficient Air Conditioning System Using Geothermal Cooling-Solar Heating in Gujarat, India

It is well known that one unit of electrical energy saved is equal to more than two units produced. One way of economizing the power is utilization of energy efficient systems at all locations. In the present study, the air conditioning system is analysed and an innovative way is suggested. We use natural low temperature of shallow sub surface (1 - 3 m) of the earth—geothermal cooling system. It is known that majority of the households and the apartment complexes in India have two tanks for water storage. One is the underground water sump and the other is the overhead water tank. In our study, we use these two water storage systems for space cooling during summer and also for heating during winter. The main aim of our paper is air-conditioning of the space in an economic way to save electricity. It is based on a simple idea of transferring the low temperature from underground water sump to the room in the house using water as a mode of transport. Since India is a tropical country located at low latitude, most of the year, the air temperature is high and demands space cooling. However, for a couple of months during severe winter months (Dec.-Jan.) at Ahmedabad, heating of the space is required. For heating the space, we suggest to use the well-known solar water heater. Effective use of heat exchanger is shown through computation, modelling schemes and lab experiment. We recommend geothermal cooling for 10 months in a year and solar hot water system during 2 months of winter. It is observed that the ambient air temperature of 35°C - 40°C in the room can be brought down to 26°C without much consumption of electricity. In a similar manner, the room temperature at night (13°C) during winter in Ahmedabad can be increased to 27°C through circulation of water from solar water heater in the heat exchanger.

Thermal Sense Prediction Model for Definite Human Group in Indoor Case

In order to build a prediction model of the indoor thermal comfort for a given human group, the original predicted mean vote （PMV） equation is reconstructed and simplified, the modified PMV equation is named PMVR （PMV for region） , where five variables are needed to be fitted with the dataset of actual thermal sense of a definite human group. As the fitting algorithm, the particle swarm optimization algorithm is used to optimize the solution, and a fixed PMVR can be finally determined. Experiment results indicate that for a definite human group, PMVR is more accurate on the prediction of thermal sense compared with some other models.

Numerical Study on the Suitability of Passive Solar Heating Technology Based on Differentiated Thermal Comfort Demand

Indoor thermal comfort and passive solar heating technologies have been extensively studied.However,few studies have explored the suitability of passive solar heating technologies based on differentiated thermal comfort demands.This work took the rural dwellings in Northwest China as the research object.First,the current indoor and outdoor thermal environment in winter and the mechanism of residents’differentiated demand for indoor thermal comfort were obtained through tests,questionnaires,and statistical analysis.Second,a comprehensive passive optimized design of existing buildings was conducted,and the validity of the optimized combination scheme was explored using DesignBuilder software.Finally,the suitability of passive solar heating technology for each region in Northwest China was analyzed based on residents’differentiated demand for indoor thermal comfort.The regions were then classified according to the suitability of the technology for these.The results showed that the indoor heating energy consumption was high and the indoor thermal environment was not ideal,yet the solar energy resources were abundant.Indoor comfort temperature indexes that match the functional rooms and usage periods were proposed.For the buildings with the optimized combination scheme,the average indoor temperature was increased significantly and the temperature fluctuation was decreased dramatically.Most regions in Northwest China were suitable for the development of passive solar heating technology.Based on the obtained suitability of the technology for the regions of Northwest China,these were classified into most suitable,more suitable,less suitable,and unsuitable regions.