Thermal Comfort Of Human Body Research Articles

Evaluation and application research on thermal comfort of mining face in hot and humid mines

The hot and humid environment in the coal mines negatively affects miners' health and mental health. This paper analyzes the factors that affect the human body heat dissipation, puts forward the concept of dressing rate, and uses the dressing rate to correct the human skin heat dissipation loss and sweat evaporation heat dissipation loss in the underground environment. A human-body thermal comfort model suitable for the hot and humid mine environment is constructed. Then the evaluation index UPMV of thermal comfort in hot and humid mines is proposed, and the mathematical model of human thermal comfort evaluation is constructed which improves the accuracy of human thermal comfort evaluation in hot and humid mines. Lastly, a software system of thermal comfort evaluation for hot and humid mines is developed, which is used to evaluate the thermal comfort of the human body at different working points of horizontal mining roadway in Shoushan mine, and the accuracy of the evaluation model is validated. The research results provide a theoretical basis for the evaluation system of human thermal comfort in hot and humid environments, and provide a reference for a scientific and reasonable arrangement of underground production.

Experimental study of a paraffin-based composite phase change material with graphite sheet, copper powder and silver copper powder

In order to study a kind of phase change material with high thermal conductivity (TC) and high latent heat (LH) of phase change used in mine cooling work clothes. This paper prepared a phase change material based on paraffin and added graphite sheet (GS) composite material with different thickness and metal (copper powder (CP), silver copper powder (SCP)) composite material, and test the thermal parameters. The results showed that the LH of the composites increased by 16 % when the thickness of GS was increased from 0.02 to 0.08 mm. And with the addition of GS, the TC of the composite was increased by 15 %. The LH of the SCP composite is greater than that of the CP composite when the metal addition is 5 %, after which the LH gradually decreases and is the same when the mass fraction of metal added is 8 %. The TC of the composite material grow from 4.451 to 6.012 W/(m⋅K) with the addition of CP; the TC of the composite material grow from 4.457 to 20.332 W/(m⋅K) with the addition of SCP. Through the performance test of the cooling clothing, the cooling clothing can effectively improve the thermal comfort of human body.

Stepless IR Chromism in Ti3 C2 Tx MXene Tuned by Interlayer Water Molecules.

Real-time control over infrared (IR) radiation of objects is highly desired in a variety of areas such as personal thermal regulation and IR camouflage. This requires the dynamic modulation of IR emissivity in a stepless manner over a wide range (>50%), which remains a daunting challenge. Here, an emissivity modulation phenomenon is reported in stacked 2D Ti3 C2 Tx MXene nanosheets, from 12% to 68% as the intercalation/discharging of water molecules within the interlayers. The intercalation of water molecules dynamically changes the electronic properties and the complex permittivity in IR frequencies of Ti3 C2 Tx . This emissivity modulation is a stepless and reversible process without the assistance of any external energy input. Further, intercalating cellulose nanofibers into the Ti3 C2 Tx interlayers makes this dynamic process highly repeatable. Last, a sweat-responsive adaptive textile that can improve thermal comfort of human body under changes in metabolic rates and environmental conditions is demonstrated, showing great potential of this mechanism in passive on-demand radiation modulation.

Photothermal Fabric Based on In Situ Growth of CuO@Cu Fractal Dendrite Fiber for Personal Thermal Management

Advanced personal thermal management fabrics are being developed to realize improved human body thermal comfort and effectively regulate heat exchange between the human body and surroundings. Fiber‐based thermal management fabrics are directly worn on soft and curved multiple curvature human body. Herein, a flexible photothermal fiber based on copper fractal dendrites with abundant CuO nanowires is designed. Well‐aligned Cu fractal dendrite fiber is electrodeposited template freely via a low‐cost and scalable process in an aqueous solution. Then, flexible CuO@Cu fractal dendritic photothermal fiber is fabricated by direct in situ oxidation and calcination of Cu fractal dendrites. Furthermore, the CuO@Cu fractal dendritic photothermal fiber can be woven into photothermal fabric by the traditional jacquard embroidery process. The temperature of photothermal fabric can be adjusted within the range of 35–65 °C by adjusting the number of photothermal fibers, which can be achieved with comfortable wearing of human thermal management and hot compress of hyperthermia to relieve local pain. Therefore, the Cu fractal dendrites have shown considerable potential for promoting the photothermal conversion of flexible personal thermal management.

Data-driven adaptive GM(1,1) time series prediction model for thermal comfort.

In this paper, the future prediction of predicted mean vote (PMV) index of indoor environment is studied. PMV is the evaluation index used in this paper to represent the thermal comfort of human body. According to the literature, the main environmental factors affecting PMV index are temperature, humidity, black globe temperature, wind speed, average radiation temperature, and clothing surface temperature, and there is a complex nonlinear relationship between the six variables. Due to the coupling relationship between the six parameters, the PMV formula can be simplified under specific conditions, reducing the monitoring of variables that are difficult to observe. Then, the improved grey system prediction model GM(1,1) with optimized selection dimension is used to predict the future time of PMV. Due to the irregularity, uncertainty and fluctuation of PMV values in time series, based on the original GM(1,1) time series prediction, an adaptive GM(1,1) improved model is proposed, which can continuously change with time series and enhance its prediction accuracy. By contrast, the improved GM(1,1) model can be derived from the sliding window of the adaptive model through changes in the dataset and get better model grades. It lays a foundation for the future research on the predicted index of PMV, so as to set and control the air conditioning system in advance, to meet the intelligence of modern intelligent home and humanized function of sensing human comfort.

Scalable nanofibrous silk fibroin textile with excellent Mie scattering and high sweat evaporation ability for highly efficient passive personal thermal management

Passive personal thermal management based on radiative cooling textiles is emerging as a facile, cost-effective, and energy-efficient way for outdoor human body thermal comfort. Existing passive radiative cooling textiles are mainly built from synthetic polymers that are usually nonrenewable and non-degradable, and lack sweat management function. Herein, we report the fabrication of a biopolymer-based, nanofibrous textile that integrates passive radiative cooling and sweat transportation functions via a scalable electrospinning technique. The optimized control over the nanofibers’ diameter enables the 200 µm thick film with high reflectance in both the ultraviolet (UV) range (92%) and the entire solar spectrum (95%), and the abundant chemical bonds of silk fibroin allow a high emissivity of 95% in the atmospheric window. Consequently, the nanostructured textile can achieve a temperature of ∼3.8 °C below the ambient temperature during the daytime and ∼6.4 °C at night. More importantly, the use of hygroscopic silk fibroin offers additional functions of sweat absorption and evaporation. Outdoor sweat evaporation experiment demonstrates a temperature reduction of ∼5.5 °C for nanofibrous silk fibroin textile, compared with the traditional nonhygroscopic textile. Owing to its excellent combination of biodegradability, superior cooling ability, and high sweat transportation capacity, the scalable silk nanofabric would be an effective textile for passive personal thermal management.

Evaluation of thermal environment and human thermal comfort in 8 types of public places from 2019 to 2021

Objective: To evaluate the thermal environment of different types of public places and the thermal comfort of employees, so as to provide scientific basis for the establishment of microclimate standards and health supervision requirements. Methods: From June 2019 to December 2021, 50 public places (178 times) of 8 categories in Wuxi were selected, including hotels, swimming pools (gymnasiums), bathing places, shopping malls (supermarkets), barber shops, beauty shops, waiting rooms (bus station) and gyms. In summer and winter, microclimate indicators such as temperature and wind speed were measured in all kinds of places, combined with the work attire and physical activity of employees in the places. Fanger thermal comfort equation and center for the built environment (CBE) thermal comfort calculation tool were used to evaluate the predicted mean vote (PMV), predicted percent dissatisfied (PPD) and standard effective temperature (SET) according to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 55-2020. The modification effects of seasonal and temperature control conditions on thermal comfort were analyzed. The consistency of GB 37488-2019 "Hygienic Indicators and Limits in Public Places" and ASHRAE 55-2020 evaluation results on thermal environment was compared. Results: The thermal sensation of hotel, barber shop staff and the gym front-desk staff were moderate, while the thermal sensation of swimming place lifeguard, bathing place cleaning staff and gym trainer were slightly warm in summer and winter. Waiting room (bus station) cleaning and working staff, shopping mall staff felt slightly warm in summer and moderate in winter. Service staff in bathing places felt slightly warm in winter, while staff in beauty salons felt slightly cool in winter. The thermal comfort compliance of hotel cleaning staff and shopping mall staff in summer was lower than that in winter (χ(2)=7.01, 7.22, P=0.008, 0.007). The thermal comfort compliance of shopping mall staff in the condition of air conditioning off was higher than that in the condition of air conditioning on (χ(2)=7.01, P=0.008). The SET values of front-desk staff in hotels with different health supervision levels were significantly different (F=3.30, P=0.024). The PPD value and SET value of the front-desk staff, and the PPD value of cleaning staff of hotels above three stars were lower than those of hotels below three stars (P<0.05). The thermal comfort compliance of front-desk staff and cleaning staff in hotels above three stars was higher than that in hotels below three stars (χ(2)=8.33, 8.09, P=0.016, 0.018). The consistency of the two criteria was highest among waiting room (bus station) staff (100.0%, 1/1) and lowest among gym front-desk staff (0%, 0/2) and waiting room (bus station) cleaning staff (0%, 0/1) . Conclusion: There are different degrees of thermal discomfort in different seasons, under the condition of air conditioning and health supervision, and the microclimate indicators can not fully reflect the thermal comfort of human body. The health supervision of microclimate should be strengthened, the applicability of health standard limit value should be evaluated in many aspects, and the thermal comfort of occupational group should be improved.

Self-repairing thermal energy storage gels demonstrating superior thermophysical properties and wearability towards personal thermal management in static and dynamic modes

It is still a big challenge to develop state-of-art thermal energy storage materials based on phase-change materials (PCMs) with superior thermophysical properties and wearability for efficient advanced personal thermal management (PTM). A novel strategy for synthesizing thermal energy storage gel with sandwich structure by confining the inorganic PCM gel in the organic PCM gel was proposed to maximize the advantages of inorganic PCMs, organic PCMs and gel materials. Octadecane and sodium sulfate decahydrate were selected as the organic PCM and inorganic PCM, respectively to satisfy the requirements of the working temperature of PTM. The thermal energy storage gels with sandwich structure demonstrate superior thermophysical properties, such as the absence of supercooling (0 °C), high latent heat (158.65 J g−1), high form-stability (no leakage), high cyclic stability (200 cycles) and high economic benefits (4.85 × 10−3 ¥ J−1). Besides, they also have excellent wearability, such as high flexibility, self-healing feature and high biocompatibility. Due to the synergistic enhancement effect and various merits, the novel thermal energy storage gels are successfully utilized in the wearable PTM for human body thermal comfort. The inorganic–organic combination methodology is promising for the highly efficient applications of PCMs in the next-generation PTM.

Fouling‐Proof Cooling (FP‐Cool) Fabric Hybrid with Enhanced Sweat‐Elimination and Heat‐Dissipation for Personal Thermal Regulation

AbstractPassive cooling fabric that facilitates sweat‐wicking and evaporation is highly desirable for promoting human body's thermal comfort and reducing energy consumption. However, highly hydrophilic sweat‐wicking fabric fails to repel external fouling due to the contradiction between hydrophilicity and lyophobicity. Moreover, conventional passive cooling fabrics show limited evaporation capacity when they reach the adsorption limit in intense perspiration scenarios. Herein, a fouling‐proof cooling (FP‐Cool) fabric with an interactive functional structure design for highly‐efficient personal thermal regulation is proposed by constructing spatially distributed superoleophobic Janus channels on an optimized heat conductive superomniphobic fabric. The dominant superomniphobicity and superoleophobic Janus feature endow the outer FP‐Cool fabric with durable performance (up to 3000 cycles’ abrasion) to repel oil/water‐based contaminations. The Janus channels rapidly pull sweat out of the inner fabric for efficient evaporation, ensuring a dry sense of skin. The FP‐Cool fabric preserves 40% higher thermal conductivity, and over 50% higher evaporation rate than conventional fabrics. In the sweat evaporation test, the FP‐Cool fabric shows up to 100% reduction in sweat gain ratio to cotton fabric. The concept would have implications for intelligent textiles design, and the synthesis strategy can be applied in various applications such as oil‐water separation and microfluidics control.

Research on thermal comfort of commercial vehicle and economy of localized air conditioning system with thermoelectric coolers

In commercial vehicles, the power consumption of the traditional air conditioning system used to cool an entire cab is high. In most cases, there is only one driver in vehicle, so adjusting the local thermal environment around the driver can reduce much energy waste. In this paper, a localized air conditioning system based on thermoelectric cooling (TEC) devices was constructed, and its performance characteristic were studied to find the optimal operating conditions in practice. The relationship between the refrigeration power and the operating current of the device was studied. A bench test was carried out to evaluate the performance of the device and the accuracy of the simulation. This paper selected a commercial vehicle cab for the application of the TEC system. The thermal comfort of human body in cab and the economy of local air conditioning system was analyzed by the method of computational fluid dynamics. The driver’s thermal comfort was analyzed based on equivalent temperature and thermal comfort deviation. The results show that when the cooling power is 3000 W, the overall thermal comfort deviation of human body under local thermoelectric refrigeration is 7.94% higher than that under traditional refrigeration. When the duty ratio of the centrifugal fan governor is about 40%–60%, the semiconductor cooling device has excellent refrigeration performance and low energy consumption, which can not only ensure the thermal comfort of the driver but also reduce the energy consumption of the air conditioner.

Watering on porous pavement for improvement of environmental human thermal comfort in an ecological community in arid area: A case study in Lanzhou, China

• A method of watering on porous pavement for improvement of thermal comfort is proposed. • Universal thermal climate index for thermal comfort evaluation is introduced. • A complex correlation coefficient with relationship between UTCI and environmental parameter is studied. A method of watering on porous pavement was put forward to improve environmental thermal comfort of human body in an ecological community arid area in Lanzhou, China. A mathematic-physical coupling model was established based on water evaporation of porous pavement. Universal thermal climate index (UTCI) was introduced to evaluate environmental thermal comfort level. Multiple linear regression analysis between meteorological factors and UTCI was conducted. A complex correlation coefficient was calculated to study relation between UTCI and each environmental parameter. Variation of environmental parameters under water evaporation on porous pavement and ordinary pavement were also compared. Watering interval based on environmental parameters for porous pavement was studied. Results show that UTCI will be in range of human thermal comfort when relative humidity reaches more than 65% under air temperature of 16 °C. Relative humidity becomes more and more sensitive to thermal comfort when air temperature is less than 20 °C. While the thermal discomfort of human body gradually increased with the increase in relative humidity when air temperature is higher than 26 °C. When air temperature is around 20 °C, watering measure should be taken. Amount of watering in a single time should meet the requirement of water evaporation for 1.67 h under local climatic weather conditions. Watering interval should be the sum of evaporation time of a single watering, and time period required for UTCI within comfortable range. Regularly watering on porous pavement can significantly improve environmental human thermal comfort in ecological community in arid areas.

Numerical and Experimental Study on Thermal Comfort of Human Body by Split-Fiber Air Conditioner

The thermal comfort of an enclosed room with air conditioner and air-distribution duct coupling can be studied, and the parameters of a split-fiber air conditioner can be optimized on the basis of studying the thermal comfort of various parts of the human body. In this paper, a room model with a distributed air conditioner was proposed. First, the rationality of the three thermal comfort characterization models of predict mean vote (PMV), predicted percentage of dissatisfied (PPD), and percentage of dissatisfied (PD) were verified through experiments and simulations. Then, the temperature and thermal comfort of various parts of the human body were explored when the air-distribution duct had different openings and different positions of the air outlet. The simulation results showed that compared with other situations, when the split-fiber air conditioner had three rows of holes (5-o’clock, 6-o’clock, 7-o’clock) and the air outlet was located in the middle of the right wall of the human body, the PMV, PPD, and PD of the measuring points around the human body fluctuated less, the indoor temperature field distribution fluctuated less, and there was no wind feeling around the human body, which can better meet the needs of human thermal comfort.

Development of photoluminescence phase-change microcapsules for comfort thermal regulation and fluorescent recognition applications in advanced textiles

To expand the application range of microencapsulated phase change materials into advanced textiles, we designed and developed a type of photoluminescence phase-change microcapsule system based on an n-eicosane core and a Eu3+-doped CaCO3/Fe3O4 composite shell. This type of functionalized phase-change microcapsules was fabricated by encapsulating n-eicosane in the CaCO3/Fe3O4 composite shell through in-situ precipitation in a Pickering emulsion-templating system, followed by doping Eu3+ on the surface of the CaCO3/Fe3O4 composite shell. The resultant microcapsules show a well-defined core–shell microstructure and regular spherical morphology with a rough surface due to the presence of Eu3+. Introducing Fe3O4 nanoparticles as a light absorber into the CaCO3 shell enhanced the utilization efficiency of solar photothermal energy for the phase-change microcapsules. The fabricated microcapsules not only exhibited a satisfactory thermal regulation capability under a latent heat capacity of over 125 J/g, but also achieved a high photothermal conversion efficiency of 67.6%. Doping Eu3+ into the CaCO3/Fe3O4 composite shell imparted a photoluminescence function to the phase-change microcapsules, resulting in a fluorescence emission at an excitation wavelength of 394 nm. An application investigation of the phase-change microcapsules in advanced textiles was carried out to confirm their contributions to the thermal comfort of human body together with high recognition under the extreme conditions. With excellent solar photothermal conversion, latent heat storage, and photoluminescence performance, the phase-change microcapsules developed by this study exhibit great potential for bifunctional applications of comfort thermal regulation and fluorescent recognition in advanced textiles.

Superhydrophobic Silica Aerogels and Their Layer-by-Layer Structure for Thermal Management in Harsh Cold and Hot Environments.

Personal thermal management (PTM) materials have recently received considerable attention to improve human body thermal comfort with potentially reduced energy consumption. Strategies include passive radiative cooling and warming. However, challenges remain for passive thermal regulation of one material or structure in both harsh hot and cold environments. In this work, silica aerogels derived from sodium silicate were prepared through a solvent-boiling strategy, where hydrophobization, solvent exchange, sodium purification, and ambient pressure drying (HSSA) proceeded successively and spontaneously in a one-pot process. This strategy leads to the synthesis of superhydrophobic silica aerogels with extremely low energy consumption without out the use of an ion-exchange resin or low surface tension solvents. Silica aerogels possess a high specific surface area (635 m2/g), high contact angle (153°), and low thermal conductivity (0.049 W/m K). A layer-by-layer (LBL) structure including the silica aerogel layer and an extra phase change material layer was designed. The structure demonstrates dual-functional thermal regulation performance in both harsh cold (-30 °C) and hot (70 °C) environments, where the time to reach equilibrium is postponed, and the inner temperature of the LBL structure can be kept above 20 °C in harsh cold environments (-30 °C) and below 31 °C in harsh hot environments (70 °C). A proof-of-concept experimental setup to simulate the illumination of sunlight also proved that the inside temperature of a model car protected by the LBL structure was below 28 °C, while the outside temperature was 70 °C. In addition, these results are well supported by theoretical COMSOL simulation results. The findings of this work not only provide an eco-friendly approach to synthesize silica aerogels but also demonstrate that the LBL structure is a robust dual-functional PTM system for thermal regulation in both harsh hot and cold environments.

Experimental Study on the Combined Heating of Phase-Change Water Tank and Different Terminal Cooling Equipment

In this paper, we set up a solar energy-phase change heat storage system and experimental study on the matching of the phase-change tank and three different terminal cooling equipment. Among them, phase-change water tank is used as heat source, meanwhile, radiator, heater and capillary as terminal cooling equipment. When radiator the terminal is radiator, the indoor temperature is difficult to meet the heating temperature requirements. When the terminal is heater, the indoor temperature can meet the requirements of heating temperature. However, the longitudinal distribution and lateral distribution of indoor air temperature are unevenly distributed and affect the thermal comfort of human body. When the terminal is capillary tube, the indoor temperature maintain at a high temperature and the temperature is satisfied with the thermal comfort of human body. Therefore, the capillary tube as the terminal cooling equipment is more advantageous of matching with the phase-change tank.

Investigation on the total and local thermal insulation of the bedding system: Effects of filling materials, weights and body postures

Thermal-insulating property of a bedding system plays a key role in affecting the sleeping thermal comfort of human body. This paper examined the impact of filling materials on the total thermal insulation of bedding system using a thermal manikin. Both the total and local thermal insulation of six down bedding systems and under four body sleeping postures were also analyzed. Besides, empirical equations for predicting the total thermal insulation of the bedding systems were developed. It was found that the total thermal insulation of bedding system with down filling was significantly higher than those of silk and wool fillings. Moreover, the total thermal insulation of the bedding system increased nonlinearly with the increasing filling weights for the sleeping postures except the supine sleeping with arms outside the quilt, which shows no thermal insulation increase above the filling weight of 600 g. The total thermal insulation measured in crouching sleeping posture was the largest, and that in supine sleeping with arms outside was the lowest, and no difference was detected between the supine sleeping and sideways sleeping postures for the different filling weights. Besides, the local thermal insulation of the bedding system is affected by the sleeping postures, quilts' filling weights and their interaction effect. This study provides solid guidelines for designing or selecting the bedding systems, and also contributes to enriching the bedding system's total and local thermal insulation database.

Experimental study on dynamic thermal environment of passenger compartment based on thermal evaluation indexes.

In this article, the thermal environment and the human thermal comfort of car cabin under different driving states in summer were studied experimentally. The weighted predictive mean vote model and the weighted equivalent temperature model were used for calculation and compared with the experimental values. The experimental results show that the air temperature and relative humidity distribution in cabin are affected by the space position and driving state. The temperature of the cabin seat, which is affected by solar radiation and crew, in the heating stage is slightly higher than the air temperature, while the cooling rate in the cooling stage is much lower than the air temperature. The predictive mean vote model and the equivalent temperature model are basically consistent with the actual thermal comfort of human body under the idle and driving conditions with the change of time. The prediction accuracy of the two models under the idle condition is higher than that under the driving condition, and the overall prediction accuracy of the equivalent temperature model is higher than that of the predictive mean vote model.

Heat exchange character and thermal comfort of young people in the building with solar radiation in winter

Indoor solar radiation notably affects the thermal environment and the character of human heat exchange with the ambient environment. Based on the field experiments of human body thermal comfort under indoor solar radiation in winter, this paper analyzes heat exchanges between the human body and the surrounding environment and the local and overall skin temperature, and discusses the relationship between heat exchange and thermal sensation. The results show that the skin temperature of the left upper arm and left thigh under radiation is 3.3 °C and 2.0 °C higher than that without radiation. As the irradiated area increases, convection and evaporation heat loss increase, and total heat loss decreases. When the thermal sensation of the human body is in a neutral state, the proportions of heat loss by convection, radiation and evaporation are 33.9%, 47.1% and 10.4%, respectively.

Optimized operation of micro grid electric heating integrated system based on PMV

The characteristics of wind power, such as peak inversion, lead to serious wind abandonment in heating season. With the implementation and use of the heat storage electric boiler (HSEB), the utilization rate of wind power can be effectively improved by establishing the electric heat combined operation system with the HSEB. When the thermal comfort of human body is considered, the heat load will be changed into elastic range, and the regulation range of heating unit will be increased. Based on the analysis of the heat transfer state of the house on the user’s side, the relationship model between the outdoor temperature and the indoor heat supply is established in this paper. On this basis, the micro grid electric heating comprehensive system with the HSEB is constructed. Taking the minimum operation cost of the system as the objective function, the economic optimal operation model of the micro grid electric heating system based on PMV is established. The feasibility of the four schemes is verified by an example. The results show that the micro grid electric heating system based on the PMV contained HSEB can accommodate the abandoned wind power, reduce the fuel cost and reduce the environmental pollution on the premise of ensuring the indoor comfort, which has a good application prospect.

Application Analysis of Artificial Environment Control System with Ultra-miniature UAV

In recent years, with the continuous development of building energy-saving technology, people are more aware of adjusting the energy-saving situation of air-conditioning system or heating system from the aspects of indoor thermal comfort and human thermal sensation. The key problem is that the thermal comfort of human body is constantly changing in the process of moving building space. Therefore, this paper puts forward a kind of assembled artificial environment control system with ultra-micro Unmanned aerial vehicle (UAV). It can adjust the thermal comfort of human body locally, reduce the running energy consumption of heating/cooling equipment, and realize building energy saving under the condition that human body can obtain the same or even better thermal comfort environment.