scholarly journals Numerical Analysis on the Cooling Performance of a Hybrid Personal Cooling System (HPCS) under Different Hot Environments

2018 ◽  
Author(s):  
Zhanxiao Kang ◽  
Xianfu Wan ◽  
Faming Wang ◽  
Uday Raj ◽  
Bin Yang
Keyword(s):  
Relative Humidity ◽  
Thermal Performance ◽  
Environmental Temperature ◽  
Cooling System ◽  
Cooling Performance ◽  
Hot Environment ◽  
Four Levels ◽  
Hot Environments ◽  
The Impact ◽  
Personal Cooling

The hybrid personal cooling system (HPCS) consisted of ventilation fans and phase change materials (PCMs) covered with insulation pads is a promising wearable cooling system to mitigate heat strain and heat-related illnesses of occupational workers with heavy labor in hot environments. Effects of clothing characteristics (e.g., thermal resistance of insulation pads, latent heat and melting temperature of PCMs) on the thermal performance of the HPCS have been investigated in detail in our previous study. Apart from the aforementioned factors, environmental conditions, i.e., environmental temperature and relative humidity, also significantly affect the thermal performance of the HPCS. In this paper, a numerical parametric study was performed to investigate the effects of the environmental temperature and relative humidity (RH) on the thermal management of the HPCS. Five levels of air temperature under environmental RH=50% were chosen (i.e., 32, 34, 36, 38 and 40 ºC) to study the impact of environmental temperature on the HPCS’s cooling performance. In addition, four levels of environmental RH at ambient temperatures of 36 and 40 ºC were selected (i.e., 30, 50, 70 and 90%) to examine the effect of RH on cooling performance of the HPCS. Results show that high environmental temperatures could accelerate the PCM melting process and thereby weaken the cooling performance of HPCS. In the moderately hot environment (36 °C), the HPCS presented good cooling performance with the maximum core temperature at around 37.5 °C during excise when the ambient RH≤70%, whereas good cooling performance could be only seen under RH≤50% in the extremely hot environment (40 °C). Thus, it may be concluded that the maximum environmental RH for the HPCS exhibiting good cooling performance decreases with the increase in the environmental temperature.

scholarly journals A Numerical Analysis of the Cooling Performance of a Hybrid Personal Cooling System (HPCS): Effects of Ambient Temperature and Relative Humidity

2020 ◽  
Vol 17 (14) ◽  
pp. 4995
Author(s):  
Pengjun Xu ◽  
Zhanxiao Kang ◽  
Faming Wang ◽  
Udayraj Udayraj
Keyword(s):  
Numerical Analysis ◽  
Relative Humidity ◽  
Ambient Temperature ◽  
Thermal Performance ◽  
Environmental Temperature ◽  
Cooling System ◽  
Cooling Performance ◽  
Hot Environment ◽  
Four Levels ◽  
Personal Cooling

Hybrid personal cooling systems (HPCS) incorporated with ventilation fans and phase change materials (PCMs) have shown its superior capability for mitigating workers’ heat strain while performing heavy labor work in hot environments. In a previous study, the effects of thermal resistance of insulation pads, and latent heat and melting temperature of PCMs on the HPCS’s thermal performance have been investigated. In addition to the aforementioned factors, environmental conditions, i.e., ambient temperature and relative humidity, also significantly affect the thermal performance of the HPCS. In this paper, a numerical parametric study was performed to investigate the effects of the environmental temperature and relative humidity (RH) on the thermal management of the HPCS. Five levels of air temperature under RH = 50% (i.e., 32, 34, 36, 38 and 40 °C) and four levels of environmental RH at two ambient temperatures of 36 and 40 °C were selected (i.e., RH = 30, 50, 70 and 90%) for the numerical analysis. Results show that high environmental temperatures could accelerate the PCM melting process and thereby weaken the cooling performance of HPCS. In the moderately hot environment (36 °C), HPCS presented good cooling performance with the maximum core temperature at around 37.5 °C during excise when the ambient RH ≤ 70%, whereas good cooling performance could be only seen under RH ≤ 50% in the extremely hot environment (40 °C). Thus, it may be concluded that the maximum environmental RH under which the HPCS exhibiting good cooling performance decreases with an increase in the environmental temperature.

scholarly journals Intermittent face cooling reduces perceived exertion during exercise in a hot environment

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Taiki Miyazawa ◽  
Mirai Mizutani ◽  
John Patrick Sheahan ◽  
Daisuke Ichikawa
Keyword(s):  
Perceived Exertion ◽  
Climatic Chamber ◽  
Ratings Of Perceived Exertion ◽  
Peak Heart Rate ◽  
Cycle Exercise ◽  
Hot Environment ◽  
Facial Cooling ◽  
Hot Environments ◽  
The Impact ◽  
Face Cooling

Abstract Background Facial cooling (FC) is effective in improving endurance exercise performance in hot environments. In this study, we evaluated the impact of intermittent short-lasting FC on the ratings of perceived exertion (RPE) during exercise. Methods Ten healthy men performed 40 continuous minutes of ergometric cycle exercise at 65% of the peak heart rate in a climatic chamber controlled at an ambient temperature of 35 °C and a relative humidity of 50%. In the control (CONT) trial, the participants performed the exercise without FC. In two cooling trials, each participant underwent 10 s of FC at 2- (FC2) and 4-min (FC4) intervals while continuing to exercise. FC was achieved by applying two soft-gel packs (cooled to 0 °C) directly and bilaterally on the forehead, eyes, and cheeks. In another cooling trial, 10 s of FC was performed at 2-min intervals using two soft-gel packs cooled to 20 °C (FC2-20). Results The RPE values in the FC4 trial were significantly lower than those in the CONT trial at 20 min (FC4, 11.6 ± 2.2 points; CONT, 14.2 ± 1.3 points; P < 0.01). Further, significant differences in the RPE values were observed between the FC4 and CONT trials at 5–15 min and 25–40 min (P < 0.05). RPE values were also significantly lower in the FC2 trial than in the CONT trial (5–40 min). Although the RPE values in the FC2-20 trial were significantly lower (5–10 min; 15–20 min) than those in the CONT trial, there were no significant differences in the RPE between the FC2-20 and CONT trials at 25–40 min. At 35 min, the RPE values were significantly higher in the FC2-20 trial than in the FC2 trial (P < 0.05). Conclusion Intermittent short-lasting FC was associated with a decrease in RPE, with shorter intervals and lower temperatures eliciting greater attenuation of increase in the RPE.

Thermal Performance Intensification of Car Radiator using SiO2/Water and ZnO/Water Nanofluids

2021 ◽  
pp. 1-25
Author(s):  
Hussein Maghrabie ◽  
Hamouda Mousa
Keyword(s):  
Heat Transfer ◽  
Working Conditions ◽  
Flow Rate ◽  
Thermal Performance ◽  
Cooling System ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Coolant Temperature ◽  
Inlet Temperature ◽  
The Impact

Abstract Recent progress in nanotechnology has lead to a revolution in the automotive cooling system. In the present work, enhancement of car radiator thermal performance was investigated using different nanofluids named SiO2/water, ZnO/water nanofluids as cooling mediums. The present study mainly aims to investigate the impact of (5 wt.%) from SiO2 and ZnO nanoparticles (NPs) dispersed in water based on car radiator heat transfer with spherical and hexagonal morphology, respectively. The experiments were performed in two working conditions of the nanofluids i.e coolant temperature and volume flow rate, moreover the present results were compared with the previous studies. The experimental working conditions were set at coolant inlet temperature (tc,i) ranged from 45 oC to 80 oC and the coolant volume flow rate (V) ranged from 3.5 lit/min to 6.5 lit/min. The experimental results show that the hexagonal ZnO/water nanofluid was superior towards enhancement of car radiator thermal performance comparing to that of SiO2 NPs. Additionally, at 6.5 lit/min and 45 °C, the enhancements of car radiator effectiveness due to using SiO2 and ZnO based water nanofluids and compared with that for the based water were 13.9% and 16%, respectively. The present study used the multiple regression analysis (MRA) and hence empirical correlations are suggested to estimate the overall heat transfer coefficient (U) for all coolants as functions of volume flow rate (V) and the coolant inlet temperature (tc,i) with a maximum STDEV of ± 1.85%.

SYNTHESIS OF ANDROGENS IN VITRO BY TESTES OF RATS ACCLIMATIZED TO A HOT ENVIRONMENT

1971 ◽  
Vol 51 (3) ◽  
pp. 489-498 ◽  
Author(s):  
E. BEDRAK ◽  
V. SAMOILOFF ◽  
U. A. SOD-MORIAH ◽  
S. GOLDBERG
Keyword(s):  
Growth Rate ◽  
Relative Humidity ◽  
Oxygen Uptake ◽  
Leydig Cells ◽  
Environmental Temperature ◽  
High Ambient Temperature ◽  
Male Rats ◽  
Similar Degree ◽  
Hot Environment

SUMMARY The relative activities of enzymes participating in the biosynthesis of testosterone via the 4-ene pathway were determined in testicular homogenates of rats acclimatized to a hot environment (33–35 °C, 25–40% relative humidity). Acclimatized animals showed an increase in activity of 17α-hydroxylase, 17,20-lyase and 20α-hydroxysteroid oxidoreductase, whereas the activity of 17β-hydroxysteroid oxidoreductase was markedly decreased. Histological examination of the testes disclosed that neither the germinal epithelium nor the Leydig cells were adversely affected by the increased environmental temperature. The results are discussed in relation to the synthesis and release of the gonadotrophins. A similar degree of acclimatization, as determined by the comparable decrease in oxygen uptake, was achieved by either of two methods: daily 4 h exposure to a high ambient temperature for 4 weeks or continuous maintenance at 35 °C. The former procedure, however, appeared to be the preferred method for acclimatization of male rats since it did not inhibit growth rate and was free of mortality.

scholarly journals Resilience of Small Ruminants to Climate Change and Increased Environmental Temperature: A Review

Animals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 867 ◽  
Author(s):  
Aleena Joy ◽  
Frank R. Dunshea ◽  
Brian J. Leury ◽  
Iain J. Clarke ◽  
Kristy DiGiacomo ◽  
...  
Keyword(s):  
Climate Change ◽  
Heat Stress ◽  
Ambient Temperature ◽  
Environmental Conditions ◽  
Environmental Temperature ◽  
Small Ruminant ◽  
Small Ruminants ◽  
Continuous Exposure ◽  
Hot Environments ◽  
The Impact

Climate change is a major global threat to the sustainability of livestock systems. Climatic factors such as ambient temperature, relative humidity, direct and indirect solar radiation and wind speed influence feed and water availability, fodder quality and disease occurrence, with production being most efficient in optimal environmental conditions. Among these climatic variables, ambient temperature fluctuations have the most impact on livestock production and animal welfare. Continuous exposure of the animals to heat stress compromises growth, milk and meat production and reproduction. The capacity of an animal to mitigate effects of increased environmental temperature, without progressing into stress response, differs within and between species. Comparatively, small ruminants are better adapted to hot environments than large ruminants and have better ability to survive, produce and reproduce in harsh climatic regions. Nevertheless, the physiological and behavioral changes in response to hot environments affect small ruminant production. It has been found that tropical breeds are more adaptive to hot climates than high-producing temperate breeds. The growing body of knowledge on the negative impact of heat stress on small ruminant production and welfare will assist in the development of suitable strategies to mitigate heat stress. Selection of thermotolerant breeds, through identification of genetic traits for adaption to extreme environmental conditions (high temperature, feed scarcity, water scarcity), is a viable strategy to combat climate change and minimize the impact on small ruminant production and welfare. This review highlights such adaption within and among different breeds of small ruminants challenged by heat stress.

scholarly journals Numerical Assessment of Earth to Air Heat Exchanger with Variable Humidity Conditions in Greenhouses

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1368
Author(s):  
Di Qi ◽  
Chuangyao Zhao ◽  
Shixiong Li ◽  
Ran Chen ◽  
Angui Li
Keyword(s):  
Heat Exchanger ◽  
Relative Humidity ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Energy Savings ◽  
Volume Flow Rate ◽  
Fluid Dynamic ◽  
Small Diameter ◽  
The Earth ◽  
The Impact

Earth to air heat exchangers are widely utilized to cool or heat passive buildings for energy savings. They often need to deal with high humidity air conditions, especially in the greenhouse due to plant transpiration, and the condensation phenomenon is frequently observed during the cooling process. To evaluate the effect of humidity and condensation on thermal performance, a three dimensional computational fluid dynamic (3D-CFD) model was developed. The distribution of relative humidity in each pipe was investigated, and the impact of inlet air relative humidity on the integrated performance of the earth to air heat exchanger was discussed. The effects of inlet air temperature and volume flow rate were also analyzed. Moreover, the influence of the heat exchanger configurations on the performance of the air condensation was researched. The results indicated that condensation had few effects on the airflow distribution uniformity of the earth to air heat exchanger, while it acted observably on the thermal performance. In addition, humid air in a small diameter pipe tended to condense more easily. Humidity and condensation should be taken into consideration for the design of earth to air heat exchangers in greenhouses during engineering applications.

scholarly journals Methods for personal cooling in hot environment used in clothing and wearables

2021 ◽  
Vol 327 ◽  
pp. 03003
Author(s):  
Atanas Vasilev ◽  
Radostina A. Angelova ◽  
Rositsa Velichkova
Keyword(s):  
Phase Change Materials ◽  
Cooling System ◽  
Cooling Water ◽  
Whole Body ◽  
Health Issues ◽  
Local Cooling ◽  
Body Cooling ◽  
Whole Body Cooling ◽  
Hot Environments ◽  
Personal Cooling

The use of an efficient personal cooling system in hot environments is becoming increasingly popular, as the increased air temperature provokes thermophysiological discomfort, heat stress, reduced productivity and could lead to several health issues. Different methods and devices for personal and local cooling have been developed over the years. The paper summarises the cooling methods applied in clothing and wearable items: phase-change materials, Peltier elements, evaporative cooling, water cooling and hybrid cooling. The local vs total (of the whole body) cooling is examined. The passive and active colling are analysed in terms of advantages, disadvantages and application.

Effects of Human Mood State in Extreme Hot Environment

2014 ◽  
Vol 522-524 ◽  
pp. 541-543 ◽  
Author(s):  
Guo Jian Li
Keyword(s):  
High Temperature ◽  
Relative Humidity ◽  
State Anxiety ◽  
Mood State ◽  
Negative Mood ◽  
Emotional Impact ◽  
Self Assessment ◽  
Hot Environment ◽  
The Impact ◽  
State Factor

To explore the effects of human mood state in extreme hot environment. The mood states of 20 healthy male volunteers were evaluated by self-assessment questionnaires, Profile of mood state (POMS) and state anxiety-inventory (S-AI), then random exposure to environmental chamber with temperature of 25°C,36°C,38°C,40°C and relative humidity of 40%,60%,80% for 1 hour. The negative mood state factor points (T,D,A,F,C) and S-AI points increased gradually as the temperature and relative humidity increased. While (V) points had a tendency to decrease, under the condition of high temperature, the relative humidity of the emotional impact is greater than the impact of high temperature on human emotions.

Investigation on the Effect of a Realistic Flow Field on the Adiabatic Effectiveness of an Effusion-Cooled Combustor

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Luca Andrei ◽  
Antonio Andreini ◽  
Cosimo Bianchini ◽  
Bruno Facchini ◽  
Lorenzo Mazzei ◽  
...  
Keyword(s):  
Flow Field ◽  
Cooling System ◽  
Acoustic Properties ◽  
Injection System ◽  
Flat Plates ◽  
Cooling Performance ◽  
Hot Gas ◽  
Adiabatic Effectiveness ◽  
The Impact ◽  
Side Flow

Effusion cooling represents the state of the art of liner cooling technology for modern combustors. This technique consists of an array of closely spaced discrete film cooling holes and contributes to lower the metal temperature by the combined protective effect of coolant film and heat removal through forced convection inside each hole. Despite many efforts reported in literature to characterize the cooling performance of these devices, detailed analyses of the mixing process between coolant and hot gas are difficult to perform, especially when superposition and density ratio effects as well as the interaction with complex gas side flow field become significant. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes, which showed higher sound absorption. The objective of this paper is to investigate the impact of a realistic flow field on the adiabatic effectiveness performance of effusion cooling liners to verify the findings available in literature, which are mostly based on effusion flat plates with aligned cross flow, in case of swirled hot gas flow. The geometry consists of a tubular combustion chamber, equipped with a double swirler injection system and characterized by 22 rows of cooling holes on the liner. The liner cooling system employs slot cooling as well: its interactions with the cold gas injected through the effusion plate are investigated too. Taking advantage of the rotational periodicity of the effusion geometry and assuming axisymmetric conditions at the combustor inlet, steady state RANS calculations have been performed with the commercial code Ansys® CFX simulating a single circumferential pitch. Obtained results show how the effusion perforation angle deeply affects the flow-field around the corner of the combustor, in particular, with a strong reduction of slot effectiveness in case of 90 deg angle value.

Investigation on the Effect of a Realistic Flow Field on the Adiabatic Effectiveness of an Effusion-Cooled Combustor

2014 ◽  
Author(s):  
L. Andrei ◽  
A. Andreini ◽  
C. Bianchini ◽  
B. Facchini ◽  
L. Mazzei ◽  
...  
Keyword(s):  
Flow Field ◽  
Cooling System ◽  
Acoustic Properties ◽  
Injection System ◽  
Flat Plates ◽  
Cooling Performance ◽  
Hot Gas ◽  
Adiabatic Effectiveness ◽  
The Impact ◽  
Side Flow

Effusion cooling represents the state of the art of liner cooling technology for modern combustors. This technique consists of an array of closely spaced discrete film cooling holes and contributes to lower the metal temperature by the combined protective effect of coolant film and heat removal through forced convection inside each hole. Despite many efforts reported in literature to characterize the cooling performance of these devices, detailed analyses of the mixing process between coolant and hot gas are difficult to perform, especially when superposition and density ratio effects as well as the interaction with complex gas side flow field become significant. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes, which showed higher sound absorption. The objective of this paper is to investigate the impact of a realistic flow field on the adiabatic effectiveness performance of effusion cooling liners to verify the findings available in literature, which are mostly based on effusion flat plates with aligned crossflow, in case of swirled hot gas flow. The geometry consists of a tubular combustion chamber, equipped with a double swirler injection system and characterized by twenty-two rows of cooling holes on the liner. The liner cooling system employs slot cooling as well: its interactions with the cold gas injected through the effusion plate are investigated too. Taking advantage of the rotational periodicity of the effusion geometry and assuming axisymmetric conditions at the combustor inlet, steady state RANS calculations have been performed with the commercial code ANSYS® CFX simulating a single circumferential pitch. Obtained results show how the effusion perforation angle deeply affects the flow-field around the corner of the combustor, in particular with a strong reduction of slot effectiveness in case of 90° angle value.

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