Neutral Air Temperature Research Articles

A field study on thermal acceptability and energy consumption of mixed-mode offices building located in the hot-dry climate of Burkina Faso

To ensure thermal comfort in hot dry climates such as the climate of Burkina Faso, occupants of buildings often rely on air conditioning systems. Defining the appropriate conditions for thermal comfort is crucial to reduce energy consumption. This paper presents the findings of a field study that aimed to assess acceptable temperatures for thermal comfort and analyze the energy consumption related to the use of air conditioning systems in a mixed-mode office building. Surveys were also conducted to gather occupants’ feedback on thermal comfort. The results of the study revealed that the average air temperature was 27.1 °C with standard deviation of 1.7 °C. Fifty-four offices were investigated and all 93 occupants to the survey consider their thermal environment comfortable. The study also identified neutral air temperature and operative temperature which are between 26.2 °C and 26.5 °C, and 26.3 °C and 26.5 °C, respectively. The results show a non-significant gap between the neutral temperature of male and female subjects. It was observed that the energy consumption for comfort is linked to the neutral temperature. These findings can serve as a starting point for establishing thermal comfort parameters for mixed-mode office buildings in Sudano-Sahelian climates having a particular socio-cultural context.

Investigation of indoor thermal comfort of heritage buildings in hot summer and cold winter zone of China: A case study

The heritage buildings of a country or region are frequently considered to be of value and significance to the current generation. This study investigates the winter indoor thermal comfort of heritage buildings in hot summer and cold winter zone of China. Field measurements and questionnaire surveys were used to conduct specific studies on the winter indoor thermal comfort of two typical traditional residential buildings (“Yinziwu” and “Diaojiaolou”) in the Yuan River basin heritage building area. The aim is to investigate the current status of building thermal comfort and provide a theoretical basis for promoting their sustainable development. The results show that 1) Indoor air temperatures in both types of buildings are significantly and positively correlated in winter, but both are below the human thermal comfort range. 2) Mean air temperatures measured in "Yinziwu" and "Diaojiaolou" are 8.8 °C and 9.4 °C, respectively, with neutral air temperatures of 11.1 °C and 13.8 °C. 3) Thermal sensation, thermal preference, and thermal comfort were significantly correlated in the two buildings, with ooccupants experiencing the coldest phase from 7:00–11:00 and the warmest phase from 15:00–19:00 daily. 4) "Yinziwu" occupants are more tolerant of the cold climate.

Predictive Capacity Analysis for Outdoor Thermal Comfort Assessments: A Case Study of Jijel City, Algeria

Ensuring acceptable thermal comfort conditions in public spaces is nowadays a major concern of urban design. A number of indices have been proposed in the literature, namely PMV, PET, SET*, UTCI, PT, mPET and MOCI. The present study aims to find the most suitable index the outdoor thermal comfort assessment in the city of Jijel by comparing the predictive capacities of these indices in terms of frequency occurrence and by relating them with the contextual responses of users. These indices are defined, their feature is analysed and finally explored. Thermal comfort based on these indices was evaluated using RayMan and Townscope softwares. The choice among these indices needs their comparison with data gathered from a survey by questionnaire. The findings indicate a slight agreement between these indices and the perceived sensation (PESV) values in the range of -1 and +1, especially with the indices SET* and mPET. However, for the classes +2 and +4, a significant disagreement is observed. For the class +3, however, only PET, PMV and SET* are more joined to the perceived sensation values. The disagreements may be related to the physical environment characteristics, the subjective perception, and the adaptation attitude of the users. Thus, further indices calibration investigation is needed for better prediction of comfort taking into account local specificities. Based on the indices which are relatively in agreement with PESV, a neutral air temperature of 19.8 °C in winter and 20.4 °C in summer for the city of Jijel is deduced. Also, a comfort zone of 17.3 to 22.4 °C in winter and 18 to 22.8 °C in summer is extrapolated.

Human thermal comfort under lateral radiant asymmetries

Occupants’ thermal comfort in buildings may be affected by the cool wall and warm wall, which is attributed to the effect of asymmetric radiation. However, the previous majority of the researches on asymmetric radiation were mainly about the comfort limits under thermally neutral condition within 1∼1.5 h but had not considered the effect of exposure duration and the condition beyond neutral. To investigate the human thermal comfort under an asymmetric environment caused by the cool wall and warm wall, forty-four subjects were exposed to neutral air temperature with lateral radiant asymmetries in winter and summer for 3 h. The results indicated that the cool wall caused thermal discomfort easier than the warm wall because the thermal sensation decreased and deviated from neutral with time. Subjects' sensitivity of local parts to asymmetric radiation was affected in the conditions beyond neutral, thus their acceptability to asymmetric radiation decreased. The currently used limits of radiant temperature asymmetry tended to underestimate the local discomfort due to the walls. For the conditions tested, The limits of 5 % dissatisfaction in radiant temperature asymmetry were 4.4 °C (180 min) and 1.8 °C (60 min and 120 min) for the warm wall, and 1.8 °C at 60 min for the cool wall.

Probability mass functions forecasting of occupants’ sensation votes under the effects of temperature, illuminance, and sound level based on ANN

Occupants' individual sensation has been usually quantified under the stimulation of single environmental factor and presented by a mean sensation vote in previous literatures. However, individual factor sensation was affected by multiple environmental factors and personal sensation vote will probably deviate considerably from a mean vote. Hence, there is an attempt to adopt Probability Mass Function (PMF) as an evaluation method for presenting the distributions of occupants' sensation vote under the simultaneous stimulation of multiple environmental parameters and predict such distributions. Our investigation firstly conducted a controlled laboratory test and collected occupants' sensation votes on thermal, acoustic, and visual environments. Subsequently, we developed, optimized, and trained three artificial neural networks (ANNs) using the collected data for predicting PMFs of occupants' 7-point sensation votes i.e., thermal sensation vote, acoustic sensation vote, and visual sensation vote, under the simultaneously stimulus of temperature, illuminance , and sound level. Finally, the ANN models were generalized to predict the PMFs of thermal, visual, and acoustic sensation vote under different environments within typical ranges of environmental factors. Results indicated that the PMFs predicted by the trained ANN models show a good agreement with the collected vote proportion distributions. Thereafter, by comparing the expected values of sensation votes under different defined conditions, it confirmed the existence of crossed and interaction effects of multiple environmental factors on human comfort. The combinations of environmental parameters that lead to a neutral sensation were illustrated as a space with small thicknesses under three-dimensional coordinate system. The neutral air temperature, illumination, and sound level are between 23 °C–24.7 °C, 580 Lux~650 Lux, and 41.5 dB–43.5 dB, respectively. Moreover, the effect directions and effect sizes of temperature, illuminance, and sound level on occupants’ sensation were numerically expressed and discussed by variable control. Suggestions on environment control strategy and further research were also provided. • Probability Mass Function (PMF) was adopted as a description method for occupants' sensation votes. • Three Three-Input Seven-Output ANN models were developed for predicting PMFs of occupants' 7-point sensation votes. • Effect directions and effect sizes of temperature, illuminance, and sound level on sensation were numerically expressed.

Neutral temperatures at 90 km altitude over Svalbard (78°N 16°E), 2002–2019, derived from meteor radar observations

Neutral air temperatures at 90 km altitude over Svalbard (78°N, 16°E) for the period 2002 to 2019 inclusive have been estimated from observations by the Nippon/Norway Svalbard Meteor Radar (NSMR). The data are presented per se and we shall not attempt to identify contributions from extra-terrestrial or anthropogenic driving. On the other hand, comparison with the corresponding period of solar UV flux notably fails to exhibit similarities. Moreover, there is indeed evidence of systematic temporal changes, possibly with a breakpoint around 2012. Selecting winter and summer months and years before and after 2012 and fitting trend-lines, we see strong evidence for cooling during summer. An apparent winter cooling prior to 2012 lacks statistical significance. A suggestion of reversal to winter warming after 2012 is also very uncertain. The summer cooling is found to be 9.9 ± 2.9 K decade−1 between 2002 and 2012, and 4.3 ± 1.2 K decade−1 between 2002 and 2019. Importantly, there is a suggestion (although lacking statistical significance) that summer cooling alleviated after 2012, and even reversed in winter.

Thermal Effects of Microwave Reduced-Graphene-Oxide Coated Polyester Fabric on a Simulated Human Skin in Cool and Neutral Air Temperatures

Batteryless wearable technology has wide applications. In particular, human body surface temperature controlling fabrics can help regulate skin temperature in heat or cold. This study investigated surface temperature distribution of the fabrics coated with reduced graphene oxide (rGO) on simulated human body skin conditions at 18 °C (cool) and 27 °C (neutral) ambient air temperatures. Polyester fabrics were spin-coated with a graphene-oxide (GO) solution of 0.2 wt%. Preparation of rGO was processed by using a microwave oven (MW-rGO). Non-treated fabric (CON) was compared to GO and MW-rGO. The surface temperature of a hot plate was maintained at 35 °C or 40 °C. The test fabrics were put on the heated hot plate or non-heated-outer portions of the hot plate. Surface temperatures of MW-rGO on the heated hot plate at an air temperature of 18 °C (cool) were higher than those of non-treated fabric (CON) under the same conditions (p < 0.01). No effects from the graphene treatment were found on non-heated portions of the graphene oxide fabric (GO) or the reduced graphene oxide fabric (MW-rGO). On the non-heated portions, surface temperatures were higher at the location closer to the hot plate compared to the location farther from the hot plate (p < 0.05). These results partially represent thermal effects of MW-rGO under a specific environment and heat source. Our findings enable an application of reduced graphene oxide to body temperature regulating clothing.

Evaluation of a new ballistic vest design for compliance with Standard No. PN-V-87000:2011 using physiological tests

Research into newly developed ballistic vests to be worn by police officers under clothing was carried out with air temperature conditions of +20 °C. A ballistic vest should incorporate protective features, comfort and ergonomics. The thermal strain on users who wore the vests was evaluated as an average and individually, after they had been conditioned in high (+50 °C), low (−40 °C) or neutral (+20 °C) air temperatures, while performing various occupational activities. Research involved six police officers aged 36–42 years, who wore civilian clothing used in moderate environmental conditions. During the tests, physiological parameters (internal temperature, local skin temperatures and amount of sweat secreted) were determined. The ease of doing exercises while wearing the vests, vest service and level of discomfort in use were assessed. Research showed that the vests tested, both as an average and individually, meet the requirements of Standard No. PN-V-87000:2011 (clause 4.5).

The effect of personal and microclimatic variables on outdoor thermal comfort: A field study in Tehran in cold season

Outdoor thermal comfort condition is examined through field surveys in Tehran, Iran, during five days of winter. Environmental monitoring has been carried out in parallel to human surveys using interviews and questionnaires with space users. Examining the climatic data in relation to subjective thermal sensation, this study confirms the significant effect of personal (age and gender) and climatic (air temperature, solar radiation, and air velocity) variables. It also determines the outdoor acceptable thermal range utilizing the index Ta, with the neutral air temperature of 14.2°C for cold season, which is then compared and justified with its indoor associated study. Finally, this research endorses environmental stimulation and expectations as two major parameters of psychological adaptation influencing thermal perception in this study.

Experimental study on the variations in human skin temperature under simulated weightlessness

To study the variations in skin temperature in weightlessness, the skin temperatures of 6 male volunteers were measured under simulated weightlessness by head down bed rest (HDBR) experiments. The effects of the air temperature, relative humidity and air speed on the mean skin temperature were scrutinized, and the regional skin temperatures of the subjects under comfortable conditions were investigated. The results showed that the mean skin temperature increased with the air temperature both before and after HDBR in low and neutral air temperatures and that the mean skin temperature was found to be higher before HDBR. However, a higher mean skin temperature was observed after HDBR when the air temperature was high. Moreover, the mean skin temperature in low and neutral air temperatures was found to increase with the relative humidity both before and after HDBR, and a higher mean skin temperature was also observed before HDBR. Additionally, a negative correlation between the mean skin temperature and air speed was observed both before and after HDBR. However, different patterns of the mean skin temperature were observed when the environment changed from low air temperature and humidity to a neutral environment and finally to a high air temperature and humidity. Finally, the regional skin temperature after HDBR showed a different distribution compared with that before HDBR, such as a higher skin temperature in the thorax, forehead and back and a lower skin temperature in the thigh, calf and hand. This indicated that the skin temperature distribution changed greatly under simulated weightlessness by HDBR, which might suggest an altered thermal regulatory mechanism in humans experiencing weightlessness.

Analysis on Thermal Comfort of Air-Conditioned Buildings in Malaysia: Case Study of Universiti Tenaga Nasional

Field study was carried out on the thermal conditions and thermal comfort of occupants in air conditioned buildings in Malaysia. The study was carried out in 10 staff offices and 6 student study areas of Universiti Tenaga Nasional (UNITEN) during October and November 2013, collecting a full set of objective physical measurements and subjective assessments through questionnaires. The measured environmental parameters were air temperature, relative humidity and air velocity. The subjective responses concern the judgment of the occupants about the thermal environment at the moment of measurements. The obtained results showed that most places are in acceptable and comfort zone according to Fanger’s predicted mean vote (PMV) model. The neutral air temperature obtained through linear regression analysis of thermal sensation vote (TSV) is 23.9°C for UNITEN. The result of this study demonstrates that the acceptability of thermal comfort among UNITEN occupant is about 78 %.

Thermal responses to different residential environments in Harbin

In China, adding space heating in residential buildings is normally scheduled at the end of October each year, with heat supplied by district heating systems. This paper describes a field study of thermal comfort conducted in Harbin during the winter from 2009 to 2010 before and after the space heating is added. The aim is to study human responses to thermal conditions in the two periods in cold climates. 23 buildings in six communities were investigated. 199 occupants from 135 families and 174 occupants from 104 families participated in the two surveys during the two periods, respectively. The neutral air temperature before adding the space heating is 25.1 °C, while during the space heating, it is 20.4 °C. The clothing insulation is 0.77 clo and 0.88 clo, respectively. If they were 0.88 clo instead of 0.77 clo before adding the space heating, the neutral air temperature should be 21.1 °C. Before and during space heating, more than 80% felt acceptable at the air temperature range between 17.5–24.0 °C and 19.0–26.5 °C for the two periods. The residents’ physiological acclimation may contribute to the differences. The preferred temperature is within the range of 23.0–24.0 °C and 21.5–24.0 °C, respectively. The preferred humidity is 47.7% and 40.5% during the two surveys. People felt cold generally before heating, while they felt comfortable at the same temperature range during space heating period. People often felt dry during heating when the relative humidity is lower than 30%, while they felt comfortable at the same relative humidity before heating.

Improved estimates for neutral air temperatures at 90 km and 78°N using satellite and meteor radar data

[1] A technique for using satellite-derived temperatures to calibrate initial estimates of 90 km temperatures measured by meteor wind radar is presented. Temperatures derived from the Nippon/Norway Svalbard Meteor Radar, situated on Svalbard at 78°N, 16°E, are calibrated using data from the Aura spacecraft's Microwave Limb Sounder (MLS) experiment. The calibration was performed in a two-step process: after an initial calibration of first-guess temperatures, results were used to adjust the MLS values to reflect daily means rather than the 0200–1100 UT observation period of the satellite instrument; thereafter the calibration was repeated with the revised MLS temperatures. The resulting temperature time series represents a marked improvement on earlier results calibrated using hydroxyl emission and potassium/K-Lidar observations, as the uncertainty is reduced from 17 to 7 K. These latest results represent a new step toward reliable and continual monitoring of upper mesosphere/lower thermosphere temperature.

On the response of the neutral temperature at 78°N and 90 km altitude to solar proton events

We are able to determine neutral air temperatures by examining the fading times of meteor trail echoes in the upper mesosphere/lower thermosphere. It has been suggested that solar proton events may stimulate both dynamic and aeronomic changes in the middle atmosphere and we have endeavoured to investigate this. Despite a variety of approaches to determine the background temperature above which we might expect to see enhancements under conditions of strong proton precipitation, we are unable to detect any significant changes. We have repeated the search during selected seasons and also with various proton flux thresholds, similarly to no avail. We conclude, therefore, that at 90 km altitude, 78°N and 16°E, at least, we are unable to detect enhanced neutral temperatures due to solar proton events. At best, any enhancements, predicted to be of the order of a few K only, are likely to be completely masked by the day-to-day variability of the temperature field.

Neutral air temperatures at 90 km and 70°N and 78°N

Meteor radars are employed to determine neutral air temperatures at 90 km altitude above Adventdalen, Spitsbergen (78°N, 16°E) and Ramfjordmoen, mainland Norway (70°N, 19°E). The philosophy underlying the temperature derivation including choice of appropriate pressure model and calibration against independent observations is discussed. Average annual variations at each of the two geographic locations are presented, indicating that current models overestimate the summer temperatures by as much as 20 K. The seasonal variation of variability of these temperatures, indicative of corresponding variation in planetary wave activity, is investigated, and in particular, we see that wave activity at 78°N is largely suppressed during summer and is otherwise characterized by a quasi 27‐day oscillation during late autumn and winter. The monthly average temperatures for 78°N presented here are proposed as a viable alternative to current semiempirical models.

Multi‐instrument derivation of 90 km temperatures over Svalbard (78°N 16°E)

For 90 km above Svalbard at 78°N, 16°E, neutral air temperatures derived from potassium lidar and OH spectrometer observations are combined and used to calibrate the corresponding estimates derived from meteor echo fading times. While lidar and spectrometer results depend heavily on observing conditions, a meteor radar can easily provide daily measurements; the three instruments thus complement each other to yield daily temperature estimates, hence providing a temporal coverage hitherto unprecedented at this location.

Meteor radar observations at middle and Arctic latitudes Part 1: mean temperatures

Observations with a Meteor radar operating at 32.55 MHz have been used to derive daily atmospheric temperature data for an altitude of 90 km at mid-latitudes during November 1999 until August 2001, and at high latitudes during September 2001 until December 2002. The neutral air temperatures are derived from determination of the ambipolar diffusion coefficient variation as a function of height, and are then corrected by application of a temperature-gradient model. The seasonal variations at both latitudes are characterized by high temperatures in winter and markedly smaller ones during summer. Whereas the winter temperatures at high latitudes are slightly warmer than at mid-latitudes by about 10 K , during summer the temperatures at high latitudes are colder by up to about 40 K . The majority of the variation in temperatures measured by this technique is due to variations in the ambipolar diffusion coefficient, but the accuracy of the temperature gradient model is important for second-order corrections. The meteor technique is valuable tool to study the short time temperature variability. The temperature data derived in this manner are in reasonable agreement with independent experimental results from different rocket, satellite and ground-based measurements, as well as with theoretical results obtained from calculations with the global circulation model COMMA-IAP.

Comment on “Neutral air turbulence and temperatures in the vicinity of polar mesosphere summer echoes” by F.‐J. Lübken, M. Rapp, and P. Hoffmann

Comment on “Neutral air turbulence and temperatures in the vicinity of polar mesosphere summer echoes” by F.‐J. Lübken, M. Rapp, and P. Hoffmann

Reply to comment by J. Klostermeyer on “Neutral air turbulence and temperatures in the vicinity of polar mesosphere summer echoes” by F.‐J. Lübken, M. Rapp, and P. Hoffmann

Reply to comment by J. Klostermeyer on “Neutral air turbulence and temperatures in the vicinity of polar mesosphere summer echoes” by F.‐J. Lübken, M. Rapp, and P. Hoffmann

Neutral air turbulence and temperatures in the vicinity of polar mesosphere summer echoes

A total of 8 sounding rocket flights with measurements of neutral air turbulence in the upper mesosphere have been performed in the past 10 years with simultaneous and nearly co‐located radar measurements of polar mesosphere summer echoes (PMSE). These measurements took place close to the rocket ranges in northern Norway (Andøya Rocket Range, 69°N) and in northern Sweden (Esrange, 68°N). A detailed comparison demonstrates that there is no apparent correlation between PMSE and neutral air turbulence and that in fact turbulence is absent in the majority of all PMSE events (no turbulence in 7 out of 10 PMSE layers). This suggests that neutral turbulence and other mechanisms affecting the neutral atmosphere at very small spatial scales play a minor role in creating PMSE, contrary to the speculations published in the literature. The main mechanism for creating PMSE remains unidentified. A comparison of PMSE with simultaneous temperature profiles derived from falling sphere and ionization gauge measurements shows that PMSE are practically always present at altitudes where the temperature is low enough for water ice particles to exist. This supports the general understanding that PMSE are closely related to charged water ice particles. On the other hand, the measurements also demonstrate that low enough temperatures are not sufficient for PMSE to exist. Temperature lapse rates were deduced from the high‐altitude‐resolution ionization gauge measurements. Within the PMSE layers the temperature lapse rate is typically +1–2 K/km with a rather large variability of ±5–10 K/km. Adiabatic lapse rates have never been found within a PMSE layer, which suggests that turbulence cannot have been active for a substantial period. This again supports the idea that neutral air turbulence plays a minor role in creating PMSE. Probably the only common physical reason for PMSE and turbulence is the background temperature profile, which supports the creation of ice particles (since temperatures are very low) and which provokes the breaking of gravity waves and creation of turbulence since the temperature gradient changes at the mesopause.