International Journal of Thermal Sciences, Nov 1, 2019
Existing clothing models assume spatial homogeneity of the enclosed air layer between skin 5 and ... more Existing clothing models assume spatial homogeneity of the enclosed air layer between skin 5 and fabric, which contradicts real-life scenarios. Furthermore, depending on the thickness of 6 enclosed air layer and the temperature difference between skin and fabric, natural convec-7 tion may occur but it is often neglected in the theoretical models. In this study, we have de-8 veloped a theoretical model that considers the spatial heterogeneity of enclosed air layer and 9 natural convection. It computes the sensible heat transfer (conduction, radiation and natural convection) in the heterogeneous enclosed and boundary air layers. The heat transfer in the clothing layer is calculated based on the thermal resistance of the fabric. The model presented in this paper is systematically validated for natural convection and spatial heterogeneity using a thermal cylinder and a thermal manikin with increasing level of spatial complexity. The validation of the model was performed for a wide range of temperatures (-10°C to 26°C), enclosed air layer thicknesses (homogeneous and heterogeneous), and ambient air speeds (0.2m/s, 1m/s) and demonstrated a good agreement between predicted and measured heat flux with an average error of 3.7% and 9.3% for homogeneous and heterogeneous enclosed air layers, respectively.
For accurate prediction of human thermal comfort in indoor space, a fully validated human body-en... more For accurate prediction of human thermal comfort in indoor space, a fully validated human body-environment interface model is the key factor. In this study, a numerical model for heat transfer simulation between the human body and the environment was developed. Three parameters, including air speed, air temperature, and total heat transfer coefficient at the body surface, were validated against experiments including a manikin placed in a climatic chamber. Based on the verified model, a set of human body-environment parameters were investigated to quantify their relevance for thermal simulations. The parameters included three body geometries with different simplification levels, three body postures, and three kinds of environments differing in room configuration, size, and wall emissivity. The investigations revealed that body geometry simplification had only a moderate influence on overall heat transfer between the body and environment, while greatly influencing local heat transfer. Body posture showed a more prominent impact on heat transfer than the geometry, especially on the radiative heat transfer, due to the view factor change caused by local body orientation. The room configuration largely influenced the airflow pattern and, thus, convective heat transfer, while room size and wall emissivity only had an influence on radiative heat transfer. A similar environmental setup and body posture with the real situation would be suggested as the premise for the bodyenvironment modelling work. The validated numerical model, along with the set of body-environment parameters, can be used for a large range of investigations on human physiological response in varying thermal environments.
To improve the measurement and subsequent use of human skin temperature (Tsk) data, there is a ne... more To improve the measurement and subsequent use of human skin temperature (Tsk) data, there is a need for practical methods to compare Tsk sensors and to quantify and better understand measurement error. We sought to develop, evaluate, and utilize a skin model with skin-like thermal properties as a tool for benchtop Tsk sensor comparisons and assessments of local temperature disturbance and sensor bias over a range of surface temperatures. Inter-sensor comparisons performed on the model were compared to measurements performed in vivo, where 14 adult males completed an experimental session involving rest and cycling exercise. Three types of Tsk sensors (two of them commercially available and one custom made) were investigated. Skin-model-derived inter-sensor differences were similar (within ±0.4 °C) to the human trial when comparing the two commercial Tsk sensors, but not for the custom Tsk sensor. Using the skin model, all surface Tsk sensors caused a local temperature disturbance wit...
In this paper, a textile-based respiratory sensing system is presented. Highly flexible polymeric... more In this paper, a textile-based respiratory sensing system is presented. Highly flexible polymeric optical fibres (POFs) that react to applied pressure were integrated into a carrier fabric to form a wearable sensing system. After the evaluation of different optical fibres, different setups were compared. To demonstrate the feasibility of such a wearable sensor, the setup featuring the best performance was placed on the human torso, and thus it was possible to measure the respiratory rate. Furthermore, we show that such a wearable system enables to keep track of the way of breathing (diaphragmatic, upper costal and mixed) when the sensor is placed at different positions of the torso. A comparison of the results with the output of some commercial respiratory measurements devices confirmed the utility of such a monitoring device.
Knowledge of an individual's skin condition is important for pressure ulcer prevention. Detec... more Knowledge of an individual's skin condition is important for pressure ulcer prevention. Detecting early changes in skin through perfusion, oxygen saturation values, and pressure on tissue and subsequent therapeutic intervention could increase patients' quality of life drastically. However, most existing sensing options create additional risk of ulcer development due to further pressure on and chafing of the skin. Here, as a first component, we present a flexible, photonic textile-based sensor for the continuous monitoring of the heartbeat and blood flow. Polymer optical fibres (POFs) are melt-spun continuously and characterized optically and mechanically before being embroidered. The resulting sensor shows flexibility when embroidered into a moisture-wicking fabric, and withstands disinfection with hospital-type laundry cycles. Additionally, the new sensor textile shows a lower static coefficient of friction (COF) than conventionally used bedsheets in both dry and sweaty conditions versus a skin model. Finally, we demonstrate the functionality of our sensor by measuring the heartbeat at the forehead in reflection mode and comparing it with commercial finger photoplethysmography for several subjects. Our results will allow the development of flexible, individualized, and fully textile-integrated wearable sensors for sensitive skin conditions and general long-term monitoring of patients with risk for pressure ulcer.
The heat and mass transfer in the functional sport and protective garments is not only affected b... more The heat and mass transfer in the functional sport and protective garments is not only affected by the fabric properties but also by air gap distribution between the body and the garment and its change. Until now several studies have been conducted to analyse the impact of clothing fit, moisture content and body posture on the distribution of the air within garment. However, used methods are limited to only a stationary position of the manikin, whereas the air gap changes dynamically with body movement during sport activities due to bending joints. The present study addressed the quantitative and comprehensive evaluation of the 3D garment simulation tool and simulation of air gap distribution change during various activities. In the first step the 3D garment simulation software was quantitatively validated by comparing these parameters obtained from this tool with the ones obtained from accurate 3D scanning method to assess its capability and accuracy [1]. Next, for the first time, ...
The concurrent development of simulation tools and thermal manikins has been progressing rapidly ... more The concurrent development of simulation tools and thermal manikins has been progressing rapidly and continuously over the past two decades. Recent advances in computation technologies have facilitated computer simulation of sophisticated human physiological regulation mechanisms at high spatial and temporal resolution. Improvements in manufacturing techniques and control strategies have resulted in the development of highly sophisticated thermal manikins. These versatile evaluation instruments combine fine spatial resolution with high measurement reliability and system responsiveness. When coupled with a thermo-physiological model, a thermal manikin becomes a human simulator that is capable of mimicking realistic dynamic human thermo-physiological responses to a given environment. There are already several such manikins in operation, mainly in clothing research field but also in built environment research. This chapter aims at discussing the opportunities and constraints of thermo-...
Abstract An analytical clothing model is developed to consider the effect of body movement on hea... more Abstract An analytical clothing model is developed to consider the effect of body movement on heat transfer. This model quantifies the impact of forced convection in an enclosed air layer and the effect of ventilation (through fabric pores and ensemble openings) on clothing insulation. The internal air speed (inside an enclosed air layer) caused by human movement is used to calculate the internal forced convective heat transfer coefficient. The model is validated for various combinations of walking speeds, ambient air speeds, and clothing fits. A validation study covering 15 experimental cases compares the local heat transfer coefficients for different parts of the body and for the entire body. These validation cases consist of standing (0 m/s) and two walking speeds (0.27 m/s, and 0.69 m/s), three ambient air speeds: still air (0.17 m/s), 1 m/s and 2 m/s, and three clothing ensembles with different designs. All the experiments were performed on an agile thermal manikin. The average relative error in simulated whole body heat flux was 11%. The presented model has ability to simulate heat transfer with high spatial resolution such as individual body segment, which is the major advantage over existing models.
As an important factor in indoor human thermal comfort, the wind is investigated in the present s... more As an important factor in indoor human thermal comfort, the wind is investigated in the present study using a fully validated human body-environment interface model based on CFD technology. The three parameters of air speed (v a , 0.5-2 m/s), turbulence intensity (TI, 5%-40%) and wind direction (0 •-180 •) were simulated to study their influence on the convective heat transfer coefficient (h c) at the surface of the human body. It was found that v a influenced the value of h c more than TI. The influence of TI on h c reached a steady level when v a was above 1.5 m/s; for example the greatest rate of change of h c at the head remained at 52% as the TI was increased from 5% to 40%. The wind direction had a noticeable influence on the overall h c when the v a was above 0.5 m/s. A 90 • wind (i.e. from the right side) gave a value of h c that was about 20% lower than wind from other directions, and led to an asymmetrical distribution of h c over the body surface. Locally, the wind direction did not influence h c at the head and feet, and influenced the central segments more than the limbs. Two regression equations for the correlations between h c and v a , TI and wind direction were also generated and validated for continuous evaluation of h c. The resulting database of values for h c can be used in combination with the human thermoregulation models for thermal response prediction in built spaces with increased air speed.
Local conditioning technologies such as seat heating and ventilation have been shown to improve t... more Local conditioning technologies such as seat heating and ventilation have been shown to improve thermal sensation and comfort, with reduced energy demands compared to conventional methods of heating and cooling. Investigation of the conditioning effectivity is demanding in terms of time and resources, as it is mainly based on human subject or thermal manikin testing. One promising method of rapidly investigating a wide range of environmental conditions is thermo-physiological and thermal sensation modelling. Until now, however, one of the most important properties of the seat, its thermal diffusivity, has been neglected in such simulations. We therefore developed a methodology that involves one-dimensional, thermal model of the seat coupled with a multi-node thermo-physiological model and thermal sensation models. The seat thermal model showed realistic predictions of heat flux in the seat contact interface for control (no conditioning), heated, and ventilated seats. The modelling results were validated against our original experimental data and data from the literature for unconditioned. The root mean square deviation (RMSD) and bias of the local skin temperatures were within the standard deviation of the measurement, typically within 1°C. In the case of the predicted local thermal sensations, we found the RMSD and bias to be below two standard deviations of the human votes in two out of three of the thermal sensation models examined. Less accurate predictions were found for the seat contact, where further model refinement is needed.
Mass transfer due to perspired moisture in a clothing system is critical for the understanding of... more Mass transfer due to perspired moisture in a clothing system is critical for the understanding of thermo-physiology and thermal protection of a clothed body. Previous studies usually investigated moisture transfer without considering the effect of liquid sweating or external heat hazards. To understand the mechanisms of sweat evaporation, accumulation and dripping with continuous sweating under radiant heat, a multi-phase experiment was designed with a sweating Torso. The concept of clothed wettedness was proposed to understand sweat evaporation of the clothed body. Results showed that the evaporation rate of the clothed body increased with increasing perspiration rate and the rate increase can be explained by the material properties (e.g., material composition, hydrophilicity and evaporative resistance ([Formula: see text])), which affected the sweat accumulation ability. Results also demonstrated a dual relationship of [Formula: see text] with the evaporation rate of the clothed b...
To evaluate the quality of new energy-saving and performance-supporting building and urban settin... more To evaluate the quality of new energy-saving and performance-supporting building and urban settings, the thermal sensation and comfort models are often used. The accuracy of these models is related to accurate prediction of the human thermo-physiological response that, in turn, is highly sensitive to the local effect of clothing. This study aimed at the development of an empirical regression model of the air gap thickness and the contact area in clothing to accurately simulate human thermal and perceptual response. The statistical model predicted reliably both parameters for 14 body regions based on the clothing ease allowances. The effect of the standard error in air gap prediction on the thermo-physiological response was lower than the differences between healthy humans. It was demonstrated that currently used assumptions and methods for determination of the air gap thickness can produce a substantial error for all global, mean, and local physiological parameters, and hence, lead to false estimation of the resultant physiological state of the human body, thermal sensation, and comfort. Thus, this model may help researchers to strive for improvement of human thermal comfort, health, productivity, safety, and overall sense of well-being with simultaneous reduction of energy consumption and costs in built environment.
Clothing and the enclosed air layers highly affect heat dissipation from the body and thus, are c... more Clothing and the enclosed air layers highly affect heat dissipation from the body and thus, are crucial factors when it comes to thermal comfort. The heat and moisture transfer is affected by the variation of the size and the shape of air gaps between the garment and the human body. In addition, the fabric and garment design properties can affect the amount of heat loss from different body parts. In this study, we investigated the effect of fabric properties (different raw materials and weave types) and the garment fit on the heat loss through the garment combinations (undershirt and shirt) for the different parts of the upper body (trunk, chest, and back) using a sweating thermal manikin. The undershirt fit and the raw material of the shirts showed strong effects on the dry thermal resistance of the garment combinations. Moreover, the undershirt properties affected the evaporative heat loss from garment combinations, and the magnitude of these effects varied over different body reg...
Perspired moisture plays a crucial role in the thermal physiology and protection of the human bod... more Perspired moisture plays a crucial role in the thermal physiology and protection of the human body wearing thermal protective clothing. Until now, the role of continuous sweating on heat transfer, when simultaneously considering internal and external heat sources, has not been well-investigated. To bridge this gap, a sweating torso manikin with 12 thermal protective fabric systems and a radiant heat panel were applied to mimic firefighting. The results demonstrated how the effect of radiant heat on heat dissipation interacted with amount of perspired moisture and material properties. A dual effect of perspired moisture was demonstrated. For hydrophilic materials, sweating induced evaporative cooling but also increased radiant heat gain. For hydrophilic station uniforms, the increment of radiant heat gain due to perspired moisture was about 11% of the increase of heat dissipation. On the other hand, perspired moisture can increase evaporative cooling and decrease radiant heat gain fo...
Thermal sensation models are commonly used to assess thermal perception in various indoor environ... more Thermal sensation models are commonly used to assess thermal perception in various indoor environments. However, using different models to evaluate the same environment can result in high discrepancies between the models' predictions, as they have been developed based on experimental data from various populations, use diverse input parameters, have different ranges of applicability and use different output scales. In this study, a validation of seven existing thermal sensation models has been performed based on literature data with regards to uniform steady-state and transient indoor environments. The environmental and personal parameters were selected following the experimental protocol and the needed thermo-physiological input parameters were obtained from a thermo-physiological model. Six models showed a good performance for the analyzed range of conditions, with a mean root-mean-square deviation equal to or lower than 1 thermal sensation unit, even beyond their original range of application. A sensitivity study towards thermo-physiological parameters was also performed, showing that the models are not equally influenced by some inaccuracies in these input parameters. Since thermal sensation models are often associated with different thermal sensation scales, the possibility of applying a scaling to the predictions has been considered. However, the scaling did not consistently improve the predictions accuracy.
One of the challenges for engineers designing indoor environments is merging the need for energy ... more One of the challenges for engineers designing indoor environments is merging the need for energy savings with providing thermally comfortable conditions for the occupants. Since the best way to evaluate thermal comfort, i.e. direct enquiry, is at the same time the most costand time-consuming one, various modelling tools are widely used. However, in order to assess complex heterogeneous environments created by novel building systems, there is a need for more sophisticated and precise tools. In this paper, we present a new human simulator methodology for indoor environmental research, combining three tools to predict thermal sensation, namely, a thermal manikin, a thermoregulation model, and a thermal sensation model. Thanks to the thermoregulation model's control, the thermal manikin is capable of mimicking the thermo-physiological response of a human exposed to chosen environmental conditions, which provides reliable input data for advanced thermal sensation models. Along with presenting this concept, the performance of a commercially available human simulator was demonstrated on five validation examples representing office-like conditions for which thermal sensation was predicted with satisfactory accuracy. Based on the presented results, we discussed the capabilities and limitations of human simulators for indoor environment research such as the benefits of performing measurements directly in the assessed environment with real garments, and the challenges related to the manikin's accuracy. The presented human simulator approach is suitable to apply in the building's design process, as well as the development of new solutions for conditioning indoor spaces, and can support the evaluation of existing buildings.
International Journal of Thermal Sciences, Nov 1, 2019
Existing clothing models assume spatial homogeneity of the enclosed air layer between skin 5 and ... more Existing clothing models assume spatial homogeneity of the enclosed air layer between skin 5 and fabric, which contradicts real-life scenarios. Furthermore, depending on the thickness of 6 enclosed air layer and the temperature difference between skin and fabric, natural convec-7 tion may occur but it is often neglected in the theoretical models. In this study, we have de-8 veloped a theoretical model that considers the spatial heterogeneity of enclosed air layer and 9 natural convection. It computes the sensible heat transfer (conduction, radiation and natural convection) in the heterogeneous enclosed and boundary air layers. The heat transfer in the clothing layer is calculated based on the thermal resistance of the fabric. The model presented in this paper is systematically validated for natural convection and spatial heterogeneity using a thermal cylinder and a thermal manikin with increasing level of spatial complexity. The validation of the model was performed for a wide range of temperatures (-10°C to 26°C), enclosed air layer thicknesses (homogeneous and heterogeneous), and ambient air speeds (0.2m/s, 1m/s) and demonstrated a good agreement between predicted and measured heat flux with an average error of 3.7% and 9.3% for homogeneous and heterogeneous enclosed air layers, respectively.
For accurate prediction of human thermal comfort in indoor space, a fully validated human body-en... more For accurate prediction of human thermal comfort in indoor space, a fully validated human body-environment interface model is the key factor. In this study, a numerical model for heat transfer simulation between the human body and the environment was developed. Three parameters, including air speed, air temperature, and total heat transfer coefficient at the body surface, were validated against experiments including a manikin placed in a climatic chamber. Based on the verified model, a set of human body-environment parameters were investigated to quantify their relevance for thermal simulations. The parameters included three body geometries with different simplification levels, three body postures, and three kinds of environments differing in room configuration, size, and wall emissivity. The investigations revealed that body geometry simplification had only a moderate influence on overall heat transfer between the body and environment, while greatly influencing local heat transfer. Body posture showed a more prominent impact on heat transfer than the geometry, especially on the radiative heat transfer, due to the view factor change caused by local body orientation. The room configuration largely influenced the airflow pattern and, thus, convective heat transfer, while room size and wall emissivity only had an influence on radiative heat transfer. A similar environmental setup and body posture with the real situation would be suggested as the premise for the bodyenvironment modelling work. The validated numerical model, along with the set of body-environment parameters, can be used for a large range of investigations on human physiological response in varying thermal environments.
To improve the measurement and subsequent use of human skin temperature (Tsk) data, there is a ne... more To improve the measurement and subsequent use of human skin temperature (Tsk) data, there is a need for practical methods to compare Tsk sensors and to quantify and better understand measurement error. We sought to develop, evaluate, and utilize a skin model with skin-like thermal properties as a tool for benchtop Tsk sensor comparisons and assessments of local temperature disturbance and sensor bias over a range of surface temperatures. Inter-sensor comparisons performed on the model were compared to measurements performed in vivo, where 14 adult males completed an experimental session involving rest and cycling exercise. Three types of Tsk sensors (two of them commercially available and one custom made) were investigated. Skin-model-derived inter-sensor differences were similar (within ±0.4 °C) to the human trial when comparing the two commercial Tsk sensors, but not for the custom Tsk sensor. Using the skin model, all surface Tsk sensors caused a local temperature disturbance wit...
In this paper, a textile-based respiratory sensing system is presented. Highly flexible polymeric... more In this paper, a textile-based respiratory sensing system is presented. Highly flexible polymeric optical fibres (POFs) that react to applied pressure were integrated into a carrier fabric to form a wearable sensing system. After the evaluation of different optical fibres, different setups were compared. To demonstrate the feasibility of such a wearable sensor, the setup featuring the best performance was placed on the human torso, and thus it was possible to measure the respiratory rate. Furthermore, we show that such a wearable system enables to keep track of the way of breathing (diaphragmatic, upper costal and mixed) when the sensor is placed at different positions of the torso. A comparison of the results with the output of some commercial respiratory measurements devices confirmed the utility of such a monitoring device.
Knowledge of an individual's skin condition is important for pressure ulcer prevention. Detec... more Knowledge of an individual's skin condition is important for pressure ulcer prevention. Detecting early changes in skin through perfusion, oxygen saturation values, and pressure on tissue and subsequent therapeutic intervention could increase patients' quality of life drastically. However, most existing sensing options create additional risk of ulcer development due to further pressure on and chafing of the skin. Here, as a first component, we present a flexible, photonic textile-based sensor for the continuous monitoring of the heartbeat and blood flow. Polymer optical fibres (POFs) are melt-spun continuously and characterized optically and mechanically before being embroidered. The resulting sensor shows flexibility when embroidered into a moisture-wicking fabric, and withstands disinfection with hospital-type laundry cycles. Additionally, the new sensor textile shows a lower static coefficient of friction (COF) than conventionally used bedsheets in both dry and sweaty conditions versus a skin model. Finally, we demonstrate the functionality of our sensor by measuring the heartbeat at the forehead in reflection mode and comparing it with commercial finger photoplethysmography for several subjects. Our results will allow the development of flexible, individualized, and fully textile-integrated wearable sensors for sensitive skin conditions and general long-term monitoring of patients with risk for pressure ulcer.
The heat and mass transfer in the functional sport and protective garments is not only affected b... more The heat and mass transfer in the functional sport and protective garments is not only affected by the fabric properties but also by air gap distribution between the body and the garment and its change. Until now several studies have been conducted to analyse the impact of clothing fit, moisture content and body posture on the distribution of the air within garment. However, used methods are limited to only a stationary position of the manikin, whereas the air gap changes dynamically with body movement during sport activities due to bending joints. The present study addressed the quantitative and comprehensive evaluation of the 3D garment simulation tool and simulation of air gap distribution change during various activities. In the first step the 3D garment simulation software was quantitatively validated by comparing these parameters obtained from this tool with the ones obtained from accurate 3D scanning method to assess its capability and accuracy [1]. Next, for the first time, ...
The concurrent development of simulation tools and thermal manikins has been progressing rapidly ... more The concurrent development of simulation tools and thermal manikins has been progressing rapidly and continuously over the past two decades. Recent advances in computation technologies have facilitated computer simulation of sophisticated human physiological regulation mechanisms at high spatial and temporal resolution. Improvements in manufacturing techniques and control strategies have resulted in the development of highly sophisticated thermal manikins. These versatile evaluation instruments combine fine spatial resolution with high measurement reliability and system responsiveness. When coupled with a thermo-physiological model, a thermal manikin becomes a human simulator that is capable of mimicking realistic dynamic human thermo-physiological responses to a given environment. There are already several such manikins in operation, mainly in clothing research field but also in built environment research. This chapter aims at discussing the opportunities and constraints of thermo-...
Abstract An analytical clothing model is developed to consider the effect of body movement on hea... more Abstract An analytical clothing model is developed to consider the effect of body movement on heat transfer. This model quantifies the impact of forced convection in an enclosed air layer and the effect of ventilation (through fabric pores and ensemble openings) on clothing insulation. The internal air speed (inside an enclosed air layer) caused by human movement is used to calculate the internal forced convective heat transfer coefficient. The model is validated for various combinations of walking speeds, ambient air speeds, and clothing fits. A validation study covering 15 experimental cases compares the local heat transfer coefficients for different parts of the body and for the entire body. These validation cases consist of standing (0 m/s) and two walking speeds (0.27 m/s, and 0.69 m/s), three ambient air speeds: still air (0.17 m/s), 1 m/s and 2 m/s, and three clothing ensembles with different designs. All the experiments were performed on an agile thermal manikin. The average relative error in simulated whole body heat flux was 11%. The presented model has ability to simulate heat transfer with high spatial resolution such as individual body segment, which is the major advantage over existing models.
As an important factor in indoor human thermal comfort, the wind is investigated in the present s... more As an important factor in indoor human thermal comfort, the wind is investigated in the present study using a fully validated human body-environment interface model based on CFD technology. The three parameters of air speed (v a , 0.5-2 m/s), turbulence intensity (TI, 5%-40%) and wind direction (0 •-180 •) were simulated to study their influence on the convective heat transfer coefficient (h c) at the surface of the human body. It was found that v a influenced the value of h c more than TI. The influence of TI on h c reached a steady level when v a was above 1.5 m/s; for example the greatest rate of change of h c at the head remained at 52% as the TI was increased from 5% to 40%. The wind direction had a noticeable influence on the overall h c when the v a was above 0.5 m/s. A 90 • wind (i.e. from the right side) gave a value of h c that was about 20% lower than wind from other directions, and led to an asymmetrical distribution of h c over the body surface. Locally, the wind direction did not influence h c at the head and feet, and influenced the central segments more than the limbs. Two regression equations for the correlations between h c and v a , TI and wind direction were also generated and validated for continuous evaluation of h c. The resulting database of values for h c can be used in combination with the human thermoregulation models for thermal response prediction in built spaces with increased air speed.
Local conditioning technologies such as seat heating and ventilation have been shown to improve t... more Local conditioning technologies such as seat heating and ventilation have been shown to improve thermal sensation and comfort, with reduced energy demands compared to conventional methods of heating and cooling. Investigation of the conditioning effectivity is demanding in terms of time and resources, as it is mainly based on human subject or thermal manikin testing. One promising method of rapidly investigating a wide range of environmental conditions is thermo-physiological and thermal sensation modelling. Until now, however, one of the most important properties of the seat, its thermal diffusivity, has been neglected in such simulations. We therefore developed a methodology that involves one-dimensional, thermal model of the seat coupled with a multi-node thermo-physiological model and thermal sensation models. The seat thermal model showed realistic predictions of heat flux in the seat contact interface for control (no conditioning), heated, and ventilated seats. The modelling results were validated against our original experimental data and data from the literature for unconditioned. The root mean square deviation (RMSD) and bias of the local skin temperatures were within the standard deviation of the measurement, typically within 1°C. In the case of the predicted local thermal sensations, we found the RMSD and bias to be below two standard deviations of the human votes in two out of three of the thermal sensation models examined. Less accurate predictions were found for the seat contact, where further model refinement is needed.
Mass transfer due to perspired moisture in a clothing system is critical for the understanding of... more Mass transfer due to perspired moisture in a clothing system is critical for the understanding of thermo-physiology and thermal protection of a clothed body. Previous studies usually investigated moisture transfer without considering the effect of liquid sweating or external heat hazards. To understand the mechanisms of sweat evaporation, accumulation and dripping with continuous sweating under radiant heat, a multi-phase experiment was designed with a sweating Torso. The concept of clothed wettedness was proposed to understand sweat evaporation of the clothed body. Results showed that the evaporation rate of the clothed body increased with increasing perspiration rate and the rate increase can be explained by the material properties (e.g., material composition, hydrophilicity and evaporative resistance ([Formula: see text])), which affected the sweat accumulation ability. Results also demonstrated a dual relationship of [Formula: see text] with the evaporation rate of the clothed b...
To evaluate the quality of new energy-saving and performance-supporting building and urban settin... more To evaluate the quality of new energy-saving and performance-supporting building and urban settings, the thermal sensation and comfort models are often used. The accuracy of these models is related to accurate prediction of the human thermo-physiological response that, in turn, is highly sensitive to the local effect of clothing. This study aimed at the development of an empirical regression model of the air gap thickness and the contact area in clothing to accurately simulate human thermal and perceptual response. The statistical model predicted reliably both parameters for 14 body regions based on the clothing ease allowances. The effect of the standard error in air gap prediction on the thermo-physiological response was lower than the differences between healthy humans. It was demonstrated that currently used assumptions and methods for determination of the air gap thickness can produce a substantial error for all global, mean, and local physiological parameters, and hence, lead to false estimation of the resultant physiological state of the human body, thermal sensation, and comfort. Thus, this model may help researchers to strive for improvement of human thermal comfort, health, productivity, safety, and overall sense of well-being with simultaneous reduction of energy consumption and costs in built environment.
Clothing and the enclosed air layers highly affect heat dissipation from the body and thus, are c... more Clothing and the enclosed air layers highly affect heat dissipation from the body and thus, are crucial factors when it comes to thermal comfort. The heat and moisture transfer is affected by the variation of the size and the shape of air gaps between the garment and the human body. In addition, the fabric and garment design properties can affect the amount of heat loss from different body parts. In this study, we investigated the effect of fabric properties (different raw materials and weave types) and the garment fit on the heat loss through the garment combinations (undershirt and shirt) for the different parts of the upper body (trunk, chest, and back) using a sweating thermal manikin. The undershirt fit and the raw material of the shirts showed strong effects on the dry thermal resistance of the garment combinations. Moreover, the undershirt properties affected the evaporative heat loss from garment combinations, and the magnitude of these effects varied over different body reg...
Perspired moisture plays a crucial role in the thermal physiology and protection of the human bod... more Perspired moisture plays a crucial role in the thermal physiology and protection of the human body wearing thermal protective clothing. Until now, the role of continuous sweating on heat transfer, when simultaneously considering internal and external heat sources, has not been well-investigated. To bridge this gap, a sweating torso manikin with 12 thermal protective fabric systems and a radiant heat panel were applied to mimic firefighting. The results demonstrated how the effect of radiant heat on heat dissipation interacted with amount of perspired moisture and material properties. A dual effect of perspired moisture was demonstrated. For hydrophilic materials, sweating induced evaporative cooling but also increased radiant heat gain. For hydrophilic station uniforms, the increment of radiant heat gain due to perspired moisture was about 11% of the increase of heat dissipation. On the other hand, perspired moisture can increase evaporative cooling and decrease radiant heat gain fo...
Thermal sensation models are commonly used to assess thermal perception in various indoor environ... more Thermal sensation models are commonly used to assess thermal perception in various indoor environments. However, using different models to evaluate the same environment can result in high discrepancies between the models' predictions, as they have been developed based on experimental data from various populations, use diverse input parameters, have different ranges of applicability and use different output scales. In this study, a validation of seven existing thermal sensation models has been performed based on literature data with regards to uniform steady-state and transient indoor environments. The environmental and personal parameters were selected following the experimental protocol and the needed thermo-physiological input parameters were obtained from a thermo-physiological model. Six models showed a good performance for the analyzed range of conditions, with a mean root-mean-square deviation equal to or lower than 1 thermal sensation unit, even beyond their original range of application. A sensitivity study towards thermo-physiological parameters was also performed, showing that the models are not equally influenced by some inaccuracies in these input parameters. Since thermal sensation models are often associated with different thermal sensation scales, the possibility of applying a scaling to the predictions has been considered. However, the scaling did not consistently improve the predictions accuracy.
One of the challenges for engineers designing indoor environments is merging the need for energy ... more One of the challenges for engineers designing indoor environments is merging the need for energy savings with providing thermally comfortable conditions for the occupants. Since the best way to evaluate thermal comfort, i.e. direct enquiry, is at the same time the most costand time-consuming one, various modelling tools are widely used. However, in order to assess complex heterogeneous environments created by novel building systems, there is a need for more sophisticated and precise tools. In this paper, we present a new human simulator methodology for indoor environmental research, combining three tools to predict thermal sensation, namely, a thermal manikin, a thermoregulation model, and a thermal sensation model. Thanks to the thermoregulation model's control, the thermal manikin is capable of mimicking the thermo-physiological response of a human exposed to chosen environmental conditions, which provides reliable input data for advanced thermal sensation models. Along with presenting this concept, the performance of a commercially available human simulator was demonstrated on five validation examples representing office-like conditions for which thermal sensation was predicted with satisfactory accuracy. Based on the presented results, we discussed the capabilities and limitations of human simulators for indoor environment research such as the benefits of performing measurements directly in the assessed environment with real garments, and the challenges related to the manikin's accuracy. The presented human simulator approach is suitable to apply in the building's design process, as well as the development of new solutions for conditioning indoor spaces, and can support the evaluation of existing buildings.
Psikuta, A., Kuklane, K., Bogdan, A., Havenith, G., Annaheim, S. and Rossi, R.M., 2016. Opportuni... more Psikuta, A., Kuklane, K., Bogdan, A., Havenith, G., Annaheim, S. and Rossi, R.M., 2016. Opportunities and constraints of presently used thermal manikins for thermo-physiological simulation of the human body. International journal of biometeorology, 60(3), pp.435-446.
Combining the strengths of an advanced mathematical model of human physiology and a thermal manikin is a new paradigm for simulating thermal behaviour of humans. However, the forerunners of such adaptive manikins showed some substantial limitations. This project aimed to determine the opportunities and constraints of the existing thermal manikins when dynamically controlled by a mathematical model of human thermal physiology. Four thermal manikins were selected and evaluated for their heat flux measurement uncertainty including lateral heat flows between manikin body parts and the response of each sector to the frequent change of the set-point temperature typical when using a physiological model for control. In general, all evaluated manikins are suitable for coupling with a physiological model with some recommendations for further improvement of manikin dynamic performance. The proposed methodology is useful to improve the performance of the adaptive manikins and help to provide a reliable and versatile tool for the broad research and development in domains of clothing, automotive and building engineering.
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Papers by Rene M Rossi
Combining the strengths of an advanced mathematical model of human physiology and a thermal manikin is a new paradigm for simulating thermal behaviour of humans. However, the forerunners of such adaptive manikins showed some substantial limitations. This project aimed to determine the opportunities and constraints of the existing thermal manikins when dynamically controlled by a mathematical model of human thermal physiology. Four thermal manikins were selected and evaluated for their heat flux measurement uncertainty including lateral heat flows between manikin body parts and the response of each sector to the frequent change of the set-point temperature typical when using a physiological model for control. In general, all evaluated manikins are suitable for coupling with a physiological model with some recommendations for further improvement of manikin dynamic performance. The proposed methodology is useful to improve the performance of the adaptive manikins and help to provide a reliable and versatile tool for the broad research and development in domains of clothing, automotive and building engineering.