Yingxin Zhu

Tsinghua University | TH · Department of Building Science and Technology

Short-term cold exposure (<1 h) may adversely affect human thermal comfort and health. Few studies have investigated the effectiveness of body heating in providing thermal protection to the torso against sharp temperature decreases, as well as the optimal operation modes of torso heating equipment. In this study, 12 male subjects were acclimatised...

Sitting after walking is a common combination of activities in temporally occupied spaces (TOSs). The heat accumulated during walking can deteriorate the thermal comfort of occupants who sit for ≤15 min in the TOSs. Compared to reducing the ambient temperature, increasing the ambient air velocity may ensure thermal comfort and energy saving in TOSs...

Walking, which is a common activity for passengers in airport terminals, has a considerable effect on passengers’ thermal comfort. Previous studies have only focused on the effect of the metabolic rate (MET) on thermal comfort. However, the role of the relative air velocity during walking cannot be ignored. To factor this, 26 healthy male subjects...

The low ambient air velocity for summer conditions (26 °C, < 0.2 m/s), currently used in Chinese airport terminals, does not meet the thermal comfort demands of passengers. Compared with reducing the ambient temperature by cooling, elevating the ambient air velocity during walking could improve thermal comfort without increasing energy consumption....

Standard effective temperature (SET) is a commonly used index in thermal comfort evaluation. It was established based on two-node model which could reflect thermal regulation process of human body. The misunderstanding and confusion of SET are always existed as its definition and calculation method are relatively complex and have been revised sever...

Passengers usually walk a long distance before arriving at the seating areas of the departure lounge in airport terminals. The current standards for airport terminals have not considered passengers' thermal comfort during the walking status and the variations in thermal comfort with the dwell time during the sedentary period after walking. Therefor...

In transportation buildings such as airport terminals and railway stations, the thermal comfort of passengers is associated with the energy consumption of HVAC systems. Previous studies did not reach consistent conclusions on the differences in thermal comfort demands of passengers with different dwell times in waiting halls. In addition, the therm...

Thermal comfort is one of the key factors affecting human sleep. This study aimed to provide new understandings on sleep thermal comfort in residential environments by investigating the characteristics of behavioral adjustments and exploring the relationship among indoor thermal environment, bed microclimate and sleep thermal comfort. Both online a...

In recent years, the construction of terminal buildings has become more and more large in China. One reason is to believe passengers prefer tall spaces, which however, will bring high energy consumption. To study the relationships between the indoor spaces of terminal buildings and passenger satisfaction, this study considered 11 terminal buildings...

Most snow games at the 2022 Winter Olympics will be held in Chongli, where the lowest temperature is predicted to reach −15 °C or even lower, according to the historical temperature data from the past ten years. Thus, audiences watching games in open-air venues might suffer from this extremely cold environment. In this study, basic analyses on the...

Mixed-mode (MM) buildings, integrating a naturally ventilated (NV) mode and an air-conditioned (AC) mode, have gained popularity in recent years. However, there is no consensus among previous studies on how to evaluate the thermal comfort of occupants of MM buildings. This study aimed to determine an optimal method for assessing the thermal comfort...

In residential buildings of the Yangtze River region in China, convective heating terminals operate intermittently, whereas radiant heating terminals function continuously. Different convective heating terminals include wall-mounted air conditioners (WMAC) and floor-standing air conditioners (FSAC). Previous thermal comfort studies comparing these...

Bed microclimate can directly affect the thermal comfort of the human body. A study combining experiments and field measurements was conducted to determine the effects of bedding insulation and indoor air temperature on bedding temperature and thermal comfort. The experiments involved varying indoor air temperatures (14, 18, 22, and 26°C) and beddi...

People's subjective response to any thermal environment is commonly investigated by using rating scales describing the degree of thermal sensation, comfort, and acceptability. Subsequent analyses of results collected in this way rely on the assumption that specific distances between verbal anchors placed on the scale exist and that relationships be...

In this study, existing thermal comfort models were reconsidered and analysed. A new predicted thermal sensation (PTS) model was developed, in which Gagge's two-node model was used for the calculation of thermal regulation. This model was established using data from the ASHRAE Global Thermal Comfort Database and the index of standard effective temp...

Clothing is important for keeping the human body warm in cold environments. In Fanger's predicted mean vote (PMV) model, clothing insulation is a single input parameter that describes the dressing status of the whole body. The objective of this study was to examine the effects of the clothing insulation distribution between half-bodies. The distrib...

Aged population is growing rapidly and aging in place is the major endowment pattern for older people. This study focused on the thermal living environments and thermal comfort of older people in their own homes. Special attention was paid to their behavioral adjustment characteristics. The longitudinal investigation was conducted from March 2018 t...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

This book presents selected papers from the 11th International Symposium on Heating, Ventilation and Air Conditioning (ISHVAC 2019), with a focus on HVAC techniques for improving indoor environment quality and the energy efficiency of heating and cooling systems. Presenting inspiration for implementing more efficient and safer HVAC systems, the boo...

This book presents selected papers from the 11th International Symposium on Heating, Ventilation and Air Conditioning (ISHVAC 2019), with a focus on HVAC techniques for improving indoor environment quality and the energy efficiency of heating and cooling systems. Presenting inspiration for implementing more efficient and safer HVAC systems, the boo...

This book presents selected papers from the 11th International Symposium on Heating, Ventilation and Air Conditioning (ISHVAC 2019), with a focus on HVAC techniques for improving indoor environment quality and the energy efficiency of heating and cooling systems. Presenting inspiration for implementing more efficient and safer HVAC systems, the boo...

Thermal discomfort is one of the main triggers for occupants’ interactions with components of the built environment such as adjustments of thermostats and/or opening windows and strongly related to the energy use in buildings. Understanding causes for thermal (dis-)comfort is crucial for design and operation of any type of building. The assessment...

The International Solar Decathlon initiated by the US Department of Energy in 2002 has been conducted for 17 years, but the literature on the use of field test big data to study the performance of design projects during the competition is scarce. This paper summarizes energy saving technologies used in past Solar Decathlons in the literature. The i...

In the theory of thermal adaption, it’s usually believed that people can adapt to the thermal environment actively from three aspects: physiology, psychology and behaviour. The purpose of this study is to explore whether there is some thermal physiological adaption on the seasonal scale. A chamber experiment was designed and conducted twice at spri...

This study uses the model of the airside concourse of a certain terminal building in China, which is under construction, and compares the indoor reverberation time with six different indoor heights and different situation of unoccupied and occupied indoor field. The results of the study show that due to the narrow design of the airside concourse an...

Energy use intensity (EUI) and indoor environmental quality (IEQ) are two key features for evaluating the operating performance of green buildings. However, few researchers have investigated the relationship between the EUI and IEQ in green buildings. In this study, 20 green office buildings from the hot-summer-cold-winter (HSCW) climate zone in Ch...

A flat-heat-pipe heating system using phase change material (PCM) and thermoelectric unit was proposed. The flat heat pipe was utilized as a heating terminal in this system, which provided for intermittent radiant heating for specialized applications. The proposed system can use solar energy to achieve a higher energy efficiency owing to the integr...

Previous thermal history usually influences current thermal sensation and thermal comfort. In reality, people can adjust their clothes, activities, and other factors to achieve a relatively comfortable state, which is different to a study in a controlled chamber. The purpose of this study is to explore the regularity of thermal history on human the...

Ceiling fans have been widely used for a long time as an effective cooling equipment to create a sustainable indoor environment. However, it is rather difficult for the current measuring techniques to capture such a complicated airflow field in a whole-room scale. In this study, a novel large-scale airflow measurement technology, quad-view color se...

Air conditioning technologies (HVAC) have dramatically shaped today's building environment. However, the mutually dependent relationship between the indoor climate experience and occupants' thermal comfort adaptation rarely been given attention. To investigate the dynamic processes of adapting to different indoor climates, two comparative thermal c...

This paper aims to review the published researches on post-occupancy performance of green buildings in terms of energy use, indoor environment quality (IEQ) and occupant satisfaction. A total of 925 related papers were searched and 106 articles were screened for deep review. The study also compared the actual operating performance of green building...

Sleep is physically, physiologically, and psychologically affected by several factors. The present study mainly focused on the effects of the pre-sleep thermal environment on sleep quality. The physical heat transfer between body and thermal environment determines the thermal state and thermal sensation of a subject, thereby physiologically affecti...

A personal comfort system for heating has the potential to maintain or even enhance the occupants’ thermal comfort in cold indoor environments. In this study, the effects of a chair with a heatable backrest and seat cushions were tested by subject experiments at 14 °C, 16 °C, and 18 °C in a climate chamber. The results reveal that compared to the w...

The human metabolic rate is probably the most fundamental but least accurately assessed parameter in thermal comfort research and practice. This study aims to test the dynamic changes of the metabolic rate and its effects on thermal comfort perception. An airtight chamber (2 × 2 × 2 m3) was utilized to measure subjects’ accumulated CO2 production,...

Recognizing the value of open-source research databases in advancing the art and science of HVAC, in 2014 the ASHRAE Global Thermal Comfort Database II project was launched under the leadership of University of California at Berkeley's Center for the Built Environment and The University of Sydney's Indoor Environmental Quality (IEQ) Laboratory. The...

Advances in heating, ventilation and air conditioning (HVAC) technologies have dramatically improved the indoor thermal environment, but attention should be paid on how this would affect building occupants’ thermal comfort perception. In this paper, we studied the mutually dependent relationship between indoor climate experience and occupants’ comf...

A prototype radiant heating terminal utilizing a thermoelectric cooling (TEC) unit and a flat heat pipe was evaluated in an experimental study to determine its working characteristics under practical operating conditions. TEC units have the advantage of having a higher coefficient of performance (COP) than electric heating terminal and a faster the...

Indoor environment, in addition to many other factors, such as emotion and body condition, can disturb an individual's sleep. This paper aimed to determine the relationship between indoor environment and sleep quality based on subjective questionnaires and objective measurements. First, a massive online investigation was conducted in China to colle...

Human individual differences widely and markedly affect thermal comfort and should be carefully considered in the design and operation of the built environment. This paper aims to list and examine the magnitude and significance of individual difference in the preferred/neutral/comfort temperature through reviewing previous climate chamber and field...

A long term field study was conducted in an office building in Guangzhou, which is located in the Hot Summer and Warm Winter climate zone of China. The study covered three seasons – summer, autumn, and winter. Physical environmental parameters were continuously recorded, while office workers filled in thermal comfort related questionnaires once a w...

Decisions made at the early design stage have tremendous impacts on building performance (energy consumption, daylight, life cycle cost, natural ventilation, sunshine hours, etc.). Owing to progress in the design process, the opportunity to improve building performance is constantly reducing, while the cost of optimization is constantly increasing....

In this paper, a dynamic heat transfer model based on thermal-electrical analogy has been built to compare convective and radiative heating systems for intermittent heating. An experiment has been set up to validate the model we built. The RMS Error was within 0.5 °C, confirming the accuracy of the model. The validated model was then applied to com...

There is still a gap in research on the impact of Chinese Green Building Three-Star evaluation standard on occupant satisfaction. This paper reports the results of a preliminary comparative analysis of the satisfaction levels of occupants in relation to the building overall, building performance and several indoor environment quality (IEQ) paramete...

The purpose of this study was to explore how the human body adapts to an environment as the temperature changes, and to describe the relationship between the objective skin temperature and subjective thermal evaluation. The influence of short-term thermal experience, which based on minutes and hours scale, could be considered on the prediction of t...

In regions with hot climate, most office buildings tend to use mechanical cooling for indoor thermal comfort, which results in high energy consumption throughout the year. In this article, we highlight a case study in an office building in Shenzhen, which is located in the Hot Summer and Warm Winter Zone of China. The building's most distinctive fe...

In this paper we explore the performance of a newly developed air conditioner which can produce different airflow modes such as dynamically changed Simulated Natural Wind (SNW) and Constant Mechanical Wind (CMW). Climate chamber experiments were conducted to study the demand for air movement and to compare the effects of SNW and CMW on human subjec...

In this paper, we explore the correlations between indoor climate change and human thermal adaptation, especially with regard to the time-scale and weighting factors of physiological adaptation. A comparative experiment was conducted in China where wintertime indoor climate in the southern region (devoid of space heating) is much colder than in the...

Along with the improvement of living quality, indoor thermal comfort has been drawing increasing attentions. In this paper, a comparison between South Europe, North America and Asia on winter indoor thermal environments, occupants' clothing insulations and their thermal sensations was conducted. The compared regions all locate in similar latitude r...

In China, winter thermal comfort is a complicated issue, due to the huge difference of outdoor temperatures between climate zones, along with the different space heating modes. The authors conducted a comparative winter thermal comfort field study in Harbin, Beijing and Shanghai, which represented the Severe Cold zone, Cold zone, and Hot Summer & C...

In light of growing concerns about climate change and energy conservation, the adaptive thermal comfort theory has become a research focus. However, to date, few about the dynamic process of human thermal adaptation has been explored. In this paper, we ask the question as to whether people accustomed to one indoor climate can readapt to another one...

Passengers in aircraft cabins are exposed to low-pressure environments. One of the missing links in the research on thermal comfort under cabin conditions is the influence of low air pressure on the metabolic rate. In this research, we simulated the cabin pressure regime in a chamber in which the pressure level could be controlled. Three pressure l...

Passengers' behavioral adjustments warrant greater attention in thermal comfort research in aircraft cabins. Thus, a field investigation on ten commercial aircrafts was conducted. Environment measurements were made and a questionnaire survey was performed. In the questionnaire, passengers were asked to evaluate their thermal comfort and record thei...

This is an analysis of the effect on the technical solutions when monetary values of externalities are included in a model for selecting air conditioning cold/heat sources. The focus of the study is on heating and cooling using conventional and seawater source heat pump systems. The included monetary values of damage to the environment and health a...

In order to obtain as much sunlight as possible, architects are chiefly concerned with the design of atrium forms and sky roofs at the stage of schematic design, with the effort of using the daylighting area in the greatest extent. Compared with previous single atrium forms, this paper focuses on the daylighting effect on double atriums. Based on t...

Research has shown that a stable thermal environment with tight temperature control cannot bring occupants more thermal comfort. Instead, such an environment will incur higher energy costs and produce greater CO2 emissions. Furthermore, this may lead to the degeneration of occupants' inherent ability to combat thermal stress, thereby weakening ther...

Fans are widely used in southeast of China to increase heat loss day and night in summer time. However, all-night rotating speed control system, which can produce sleep-friendly airflow, has not been proposed under rigorous human experimental results. Sleeping mode, nowadays, prevailing on the market, are figured out by testing, to be a variant of...

To investigate whether occupants' anticipated control of their thermal environment can influence their thermal comfort, and to explain why the acceptable temperature range in naturally ventilated environments is greater than that in air-conditioned environments, a series of experiments was conducted in a climate chamber in which the thermal environ...

A field study was conducted in ten apartment residences in Beijing for an entire winter. Among the residences, five were supplied by district heating (DH) and the other five utilized individual heating (IH). Indoor environmental variables were measured by self-recording instruments, and the thermal comfort situation of residents was investigated th...

Although the adaptive comfort model has gained unprecedented popularization during the past few decades, the mechanism behind the model, especially with regard to certain key hypotheses, still requires further clarification. To validate whether people with greater individual control tend to attain comfort state in wider ranges of indoor thermal env...