An investigation of thermophysiological responses of human while using four personal cooling strategies during heatwaves

A systematic review of Personal Comfort Systems from a post-phenomenological view

Personal Comfort Systems (PCS) are equipments that heat and/or cool occupants without affecting surrounding environments, ranging from commonly used devices to innovative technologies, and that tend to be controlled by people. These systems aim to address energy consumption and occupant satisfaction issues related to centralised air-conditioning. Although there are systematic studies on these systems, there is a lack of documentation regarding mediation characteristics between people and the built environment. This article presents a systematic review of PCS using a search of academic literature and patents, classifying PCS based on thermal categories and device typologies while introducing post-phenomenological mediation categories. The results show that most PCS fall into the thermal categories of 'Heating' and 'Cooling and ventilation'. The review also presents a view of the PCS territory based on mediation attributes and technological complexity. Finally, the PCS' characteristics are discussed based on the post-phenomenological concepts of Embodiment, Hermeneutic, and Background providing insights for future research opportunities and PCS development.

Mitigating heat effects in the workplace with a ventilation jacket: Simulations of the whole-body and local human thermophysiological response with a sweating thermal manikin in a warm-dry environment

Climate change is increasingly affecting human well-being and will inevitably impact on occupational sectors in terms of costs, productivity, workers' health and injuries. Among the cooling garment developed to reduce heat strain, the ventilation jacket could be considered for possible use in workplaces, as it is wearable without limiting the user's mobility and autonomy. In this study, simulations with a sweating manikin are carried out to investigate the effects of a short-sleeved ventilation jacket on human thermophysiological responses in a warm-dry scenario. Simulations were performed in a climatic chamber (air temperature = 30.1 °C; air velocity = 0.29 m/s; relative humidity = 30.0 %), considering two constant levels of metabolic rate M (M1 = 2.4 MET; M2 = 3.2 MET), a sequence of these two (Work), and three levels of fan velocities (lf = 0; lf=2; lf=4). The results revealed a more evident impact on the mean skin temperature (Tsk) compared to the rectal temperature (Tre), with significant decreases (compared to fan-off) at all M levels, for Tsk from the beginning and for Tre from the 61st minute. Skin temperatures of the torso zones decreased significantly (compared to fan-off) at all M levels, and a greater drop was registered for the Back. The fans at the highest level (lf=4) were significantly effective in improving whole-body and local thermal sensations when compared to fan-off, at all M levels. At the intermediate level (lf=2), the statistical significance varied with thermal zone, M and time interval considered. The results of the simulations also showed that the Lower Torso needs to be monitored at M2 level, as the drop in skin temperature could lead to local overcooling and thermal discomfort. Simulations showed the potential effectiveness of the ventilation jacket, but human trials are needed to verify its cooling power in real working conditions.

Application of the thermoelectric cooling system in making a cooling belt: A case of heat stress control measure device

BACKGROUND

Climate change and global warming are emerging as new challenges worldwide. The World Meteorological Organization has reported that the temperature is expected to rise by an average of 1.2°C between 2021-2025. This increase in temperature will expose more and more workers to extreme heat.

OBJECTIVE

This study aimed to explore the possibility of using thermoelectric coolers for cooling the water circulation circuit of a cooling belt, which can be used for extended periods in high-temperature environments.

METHODS

A cooling belt was designed using thermoelectric coolers (TEC) and two blowers. The TECs were equipped with heat sinks and heat exchange block made of aluminum at hot and cold sides to exchange heat effectively.

RESULTS

The experiment was conducted under actual environmental temperature conditions during three different time periods, with mean temperatures of 31, 48, and 41°C. The mean temperature of the belt section was recorded as 20.73, 24.52, and 21.38°C, respectively. The maximum average difference between the inlet air temperature and the inside cooling belt temperature was 40.45°C.

CONCLUSION

The experiment revealed that the cooling performance of the designed prototype remained within an acceptable range (18°C) despite the increase in ambient temperature. Moreover, the cooling system can be utilized in high-heat environments to reduce thermal stress.

Efficacy of cooling vests based on different heat-extraction concepts: The HEAT-SHIELD project

INTRODUCTION

A wide range of cooling vests for heat-strain mitigation purposes during physical work are available on the market. The decision regarding the optimal cooling vest/concept for a specific environment can be challenging by relying solely on the information provided by the manufacturers. The aim of this study was to investigate how different types of cooling vests would manifest/perform in a simulated industrial setting, in a warm and moderately humid environment with low air velocity.

METHODS

Ten young males completed six experimental trials, including a control trial (no vest) and five trials with vests of different cooling concepts. Once entering the climatic chamber (ambient temperature: 35 °C, relative humidity: 50 %), participants remained seated for 30 min to induce passive heating, after which they donned a cooling vest and started a 2.5-h of walk at 4.5 km·h^-1. During the trial, torso skin temperature (T_sk), microclimate temperature (T_micro) and relative humidity (RH_micro), as well as core temperature (rectal and gastrointestinal; T_c) and heart rate (HR) were measured. Before and after the walk, participants conducted different cognitive tests and provided subjective ratings throughout the walk.

RESULTS

The use of the vests attenuated the increase in HR (103 ± 12 bpm) when compared to control trial (116 ± 17 bpm, p < 0.05). Four vests maintained a lower torso T_sk (31.7 ± 1.5 °C) compared to control trial (36.1 ± 0.5 °C, p < 0.05). Two vests using PCM inserts attenuated the increase in T_c between 0.2 and 0.5 °C in relation to control trial (p < 0.05). Cognitive performance remained unchanged between the trials. Physiological responses were also well reflected in subjective reports.

CONCLUSION

Most vests could be considered as an adequate mitigation strategy for workers in industry under the conditions simulated in the present study.

Effects of liquid cooling garment on physiological and psychological strain of firefighter in hot and warm environments

This study aimed to explore the effects of a liquid cooling garment on the physiological and psychological strains of firefighters. Twelve participants wearing firefighting protective equipment with the liquid cooling garment (LCG group) and without the liquid cooling garment (CON group) were recruited to conduct human trials in a climate chamber. During the trials, physiological parameters (mean skin temperature (T_sk), core temperature (T_c), and heart rate (HR)) and psychological parameters (thermal sensation vote (TSV), thermal comfort vote (TCV), and rating of perceived exertion (RPE)) were measured continuously. The heat storage, sweating loss, physiological strain index (PSI), and perceptual strain index (PeSI) were calculated. The results indicated that the liquid cooling garment decreased the mean skin temperature (maximum value of 0.62 °C), scapula skin temperature (maximum value of 1.90 °C), sweating loss (26%), and PSI (0.95 scales) with a significant difference (p < 0.05) at some time points when compared with the CON group. Moreover, the liquid cooling garment had little influence (p > 0.05) on core temperature, heart rate, TSV, TCV, RPE, and PeSI. The association analysis indicated that psychological strain had the potential to predict physiological heat strain with an R² value of 0.86 between the PeSI and PSI. This study offers insights into the evaluation of cooling system performance, the design of next-generation cooling systems, and the improvement of firefighters' benefits.

Effect of Cooling Blanket on the Heat Stress of Horses in Hot and Humid Environments

Simple Summary

Heat stress is serious problem for livestock. While riding horses and racehorses spend the majority of their days in stalls, there are few reports on effective methods for reducing stall heat stress. The aim of the present study was to evaluate the effectiveness of an ice horse blanket in hot and humid environments. Twenty healthy horses were measured first without the blanket (C) and then measured with the blanket (IB), or vice versa, in a cross-over trial. The blanket was designed to keep cooling the front back, the rear back, and the loin. The skin surface temperature of the front back was decreased with cooling time in IB, whereas it was not changed in C. Similarly, respiratory rate and plasma cortisol level also decreased only in IB. The blanket used in the present study had the advantage of allowing for gentle cooling of the horse’s body without the use of water or fans. Applying this methodology should enable effective reduction of heat stress not only in horses but also in other mammals kept in barns.

Abstract

Heat stress is serious problem for livestock. While riding horses and racehorses spend the majority of their days in stalls, there are few reports on effective methods for reducing stall heat stress. The aim of the present study was to evaluate the effectiveness of an ice horse blanket in hot and humid environments. Twenty healthy horses were measured first without the blanket (C) and then measured with the blanket (IB), or vice versa, in a cross-over trial. The blanket was designed to keep cooling the front back, the rear back, and the loin. Skin surface temperature, respiratory rate, rectal temperature, and plasma cortisol level in both C and IB were measured at 10:00, 12:30, and 15:00. The skin surface temperature of the front back was decreased with cooling time in IB, whereas it was not changed in C. Similarly, heart rate, respiratory rate, and plasma cortisol level also decreased only in IB. The blanket used in the present study had the advantage of allowing for gentle cooling of the horse’s body without the use of water or fans. Applying this methodology should enable effective reduction of heat stress not only in horses but also in other mammals kept in barns.

A fan-attached jacket worn in an environment exceeding body temperature suppresses an increase in core temperature

We examined whether blowing hot air above body temperature under work clothing may suppress core temperature. Nine Japanese men engaged in two 30-min bicycle ergometer sessions at a workload of 40% VO₂max at 40 °C and 50% relative humidity. The experiment was conducted without wearing any cooling apparatus (CON), wearing a cooling vest that circulated 10.0 °C water (VEST), and wearing a fan-attached jacket that transferred ambient air underneath the jacket at a rate of 30 L/s (FAN). The VEST and FAN conditions suppressed the increases of rectal temperature (CON, VEST, FAN; 38.01 ± 0.19 °C, 37.72 ± 0.12 °C (p = 0.0076), 37.54 ± 0.19 °C (p = 0.0023), respectively), esophageal temperature (38.22 ± 0.30 °C, 37.55 ± 0.18 °C (p = 0.0039), 37.54 ± 0.21 °C (p = 0.0039), respectively), and heart rate (157.3 ± 9.8 bpm, 136.9 ± 8.9 bpm, (p = 0.0042), 137.5 ± 6.5 bpm (p = 0.0023), respectively). Two conditions also reduced the estimated amount of sweating and improved various subjective evaluations. Even in the 40 °C and 50% relative humidity environment, we may recommend wearing a fan-attached jacket because the heat dissipation through evaporation exceeded the heat convection from the hot ambient air.

Advanced Functional Materials for Intelligent Thermoregulation in Personal Protective Equipment

The exposure to extreme temperatures in workplaces involves physical hazards for workers. A poorly acclimated worker may have lower performance and vigilance and therefore may be more exposed to accidents and injuries. Due to the incompatibility of the existing standards implemented in some workplaces and the lack of thermoregulation in many types of protective equipment that are commonly fabricated using various types of polymeric materials, thermal stress remains one of the most frequent physical hazards in many work sectors. However, many of these problems can be overcome with the use of smart textile technologies that enable intelligent thermoregulation in personal protective equipment. Being based on conductive and functional polymeric materials, smart textiles can detect many external stimuli and react to them. Interconnected sensors and actuators that interact and react to existing risks can provide the wearer with increased safety, protection, and comfort. Thus, the skills of smart protective equipment can contribute to the reduction of errors and the number and severity of accidents in the workplace and thus promote improved performance, efficiency, and productivity. This review provides an overview and opinions of authors on the current state of knowledge on these types of technologies by reviewing and discussing the state of the art of commercially available systems and the advances made in previous research works.

Cooling efficiency of vests with different cooling concepts over 8-hour trials

As frequency and severity of heat waves are increasing, personal cooling systems are being considered as a tool to mitigate heat strain in workers in various occupational settings. This study assessed cooling capacities (C; W·h·m^-2) of various commercially available vests using different cooling concepts. Measurements were conducted over 8 h in a climatic chamber (Ta: 35 °C, RH: 35 %) using a thermal manikin (Ts: 35 °C). Cooling power (P) and duration of efficient cooling (t_c) determined the C value of each vest. Among the cooling concepts the active cooling vests were the most efficient, extracting 331 W·h·m^-2, followed by the vests with phase change material (PCM) inserts, hybrid and evaporative vests, extracting a maximum of 164 W·h·m^-2, 146 W·h·m^-2 and 113 W·h·m^-2, respectively. While some vests with PCM inserts provided intense but shorter cooling, evaporative vests provided mild but longer cooling throughout. Practitioner summary: The study assessed the cooling capacity of commercially available vests, using a thermal manikin. The vests present an affordable solution in various occupational settings where air-conditioning is not an option. A range of cooling capacities among different cooling concepts and vests of the same category were noted. Abbreviations: ACVs: air-cooled vests; LCVs: liquid-cooled vests; ECVs: evaporative cooling vests; HCVs: hybrid cooling vests; PCVs: phase-change cooling vests; PCM: phase change material; C: cooling capacity; Rt: thermal resistance; Re: evaporative resistance; Re (%): relative evaporative resistance; P: cooling power; P_max: maximal cooling power; P_avg: average cooling power; t_c: cooling duration; AUC: area under the curve; Ta: ambient temperature; RH: relative humidity; v_a: chamber air flow; Ts: manikin surface temperature.

Effect of cooling strategies on overall performance of a hybrid personal cooling system incorporated with phase change materials (PCMs) and electric fans

The effect of four cooling strategies on cooling performance of a hybrid personal cooling system (HPCS) incorporated with phase change materials (PCMs) and electric fans in a hot environment (i.e., T_air = 36 ± 0.5 °C, RH = 59 ± 5%) was investigated. Twelve healthy young male participants underwent four 90-min trials comprising 70 min walking and 20 min resting periods. Cooling strategies adopted in this work were CON (control), PCM-control (PCMs were removed at the end of exercise), Fan-control (fans were switched OFF during the initial 20 min) and PCM&Fan-control (fans were turned ON after 20 min exercising and PCMs were removed after the 70-min exercise). Results demonstrated that the control of electric fans could suppress the mean skin temperature rise to 34.0 °C by over 15 min and also cut down the energy consumption of the HPCS from 15.6 W h to 12.1 W h over the entire 90-min trials. Thus, it is recommended that fans should be turned off at the beginning of hot exposure and switched on once participants felt warm. Our findings also showed that the removal of fully melted PCM packs from the HPCS could enhance the evaporative cooling effect brought about by air circulation. The removal of melted PCMs significantly reduced the physical load by 37.3% and ratings of perceived exertion (RPE) were decreased by 3.5-4.2 RPE units. This could also help quickly restore the PCM energy for future usage. In summary, cooling strategies demonstrated in this work could improve HPCS's overall cooling performance on workers while working in the studied hot environment.

Design and evaluation of cooling workwear for miners in hot underground mines using PCMs with different temperatures

Cooling workwear using phase change materials (PCMs) was designed for miners in hot underground mines. A new arrangement of PCM packs was introduced that used 15 °C PCMs as the inner layer and 23 °C PCMs as the outer layer (15&23). Its performance was investigated using thermal manikin and human subject tests by comparison with clothing without PCMs (CON), with 15 °C PCMs (15&15) and with melted PCMs (mPCM) in a climate chamber (30 °C, 80% relative humidity). The PCM cooling workwear significantly increased the manikin heat loss, attenuated the rise of skin temperatures and improved thermal sensation and comfort. The cooling duration was extended in 15&23 as compared with 15&15. The added PCMs did not affect the perceptual exertion and body mobility. In summary, cooling workwear using PCMs with different temperatures can be an effective option for miners' personal cooling in a hot and humid environment.

Performance enhancement of hybrid personal cooling clothing in a hot environment: PCM cooling energy management with additional insulation

A novel design of personal cooling clothing incorporating additional insulation sandwiched between phase change materials (PCMs) and clothing outer layer is proposed. Performance of four personal cooling systems including clothing with only PCMs, clothing with PCMs and insulation (PCM + INS), clothing with PCMs and ventilation fans (HYB), and clothing with PCMs, ventilation fans and insulation (HYB + INS) was investigated. Effect of additional insulation on clothing cooling performance in terms of human physiological and perceptual responses was also examined. Human trials were carried out in a hot environment (i.e. 36 °C, RH = 59%). Results showed that significantly lower mean skin/torso temperatures were registered in HYB + INS as compared to HYB. In contrast, no significant effect of the use of insulation on both skin and body temperatures between PCM and PCM + INS was observed. Also, no significant difference in thermal sensations, thermal comfort, and skin wetness sensation was registered between cooling systems with and without additional insulation. Practitioner Summary: Hybrid personal cooling clothing has shown the ability to provide a relatively cool microclimate around the wearer' body while working in hot environments. The present work addresses the importance of cooling energy saving for PCMs in a hot environment. This work contributes to optimising cooling performance of hybrid personal cooling systems.

Intermittent wetting clothing as a cooling strategy for body heat strain alleviation of vulnerable populations during a severe heatwave incident

Many documented studies have demonstrated the human mortality rate increases during severe heatwaves. There remains a need for further explore ecologically valid cooling strategies to alleviate body heat strain during extreme heatwaves. The main aim of this work was to explore whether intermittent wetting clothing can be served as an ecologically valid cooling strategy to mitigate heat stress on inactive vulnerable populations not having access to air-conditioning during a severe heatwave. Ten young male subjects underwent two 90-min separate trials: a dry clothing trial (i.e., CON) and a wetted clothing cooling trial (i.e., WEC). A set of light summer wear was chosen and intermittently wetted by tap water at intervals of every 30 min. Physiological and perceptual responses of subjects were examined and compared. All trials were performed in a chamber with an air temperature of 43 ± 0.5 °C, RH= 57 ± 5% and an air velocity of 0.15 ± 0.05 m/s (WBGT=37.35 °C). Results demonstrated that WEC, compared with CON, could significantly reduce both the mean skin temperature and the core temperature throughout the 5-90th min and 25-90th min of the trial, respectively (p < 0.05). Besides, WEC could also remarkable reduce local skin temperatures at those body sites covered by wet clothing (p < 0.05). In comparison, no significant difference was found between WEC and CON on perceptual responses. Further, it was also found from PHS simulations that conditions with a partial water vapour pressure ≤ 3.1-3.5 kPa would not induce pronounced core temperature rises at 43 °C. Finally, it may be concluded that intermittent wetting clothing could be served as an ecologically valid cooling strategy to reduce thermophysiological strain of vulnerable populations while seating during humid heatwaves and thereby improve their health and safety.

Comfort, Energy Efficiency and Adoption of Personal Cooling Systems in Warm Environments: A Field Experimental Study

It is well known that personal cooling improves thermal comfort and save energy. This study aims to: (1) compare different personal cooling systems and (2) understand what influences users' willingness to adopt them. A series of experiments on several types of personal cooling systems, which included physical measurements, questionnaires and feedback, was conducted in a real office environment. The obtained results showed that personal cooling improved comfort of participants in warm environments. Then an improved index was proposed and used to compare different types of personal cooling systems in terms of comfort and energy efficiency simultaneously. According to the improved index, desk fans were highly energy-efficient, while the hybrid personal cooling (the combination of radiant cooling desk and desk fan) consumed more energy but showed advantages of extending the comfortable temperature range. Moreover, if personal cooling was free, most participants were willing to adopt it and the effectiveness was the main factor influencing their willingness, whereas if participants had to pay, they probably refused to adopt it due to the cost and the availability of conventional air conditioners. Thus, providing effective and free personal cooling systems should be regarded as a better way for its wider application.