Effect of humidity on human comfort and productivity after step changes from warm and humid environment

Subjective experiments were conducted to evaluate the effects of humidity on human comfort and productivity under transient conditions from hot and humid environment to thermally neutral condition. Two climate chambers, “Chamber 1” and “Chamber 2”, adjoined each other were used for this study. Subjects were exposed to 30 °C/70%RH air in Chamber 1 for 15 min with 2.0 met of metabolic rate. Then they moved into Chamber 2, where 4 humidity conditions, 30, 40, 50 and 70%RH were examined. Air temperature was adjusted to keep SET* constant at 25.2 °C for all conditions. Subjects were exposed in Chamber 2 for 180 min performing 2 kinds of simulated office work.

Positive effects of low humidity on subjective pleasantness were found under transient condition at low humidity due to more evaporation from human body, while no significant difference in thermal sensation and humidity sensation among 4 relative humidity levels was obtained. Subjective performance was found to be at the same level under all conditions. However, subjects reported to be more tired at 70%RH after humidity step change.     

Assessment of thermal environment using a thermal manikin in a field environment chamber served by displacement ventilation system

This paper presents a thermal comfort study using a thermal manikin in a field environment chamber served by the Displacement Ventilation (DV) system. The manikin has a female body with 26 individually heated and controlled body segments. The manikin together with subjects was exposed to 3 levels of vertical air temperature gradients, nominally 1, 3 & 5 K/m, between 0.1 and 1.1 m heights at 3 room air temperatures of 20, 23 and 26 °C at 0.6 m height. Relative humidity at 0.6 m height and air velocity near the manikin and the subjects were maintained at 50% and less than 0.2 m/s, respectively. The aims of this study are to assess thermally non-uniform environment served by DV system using the manikin and correlate the subjective responses with measurements from the manikin. The main findings indicate that room air temperature had greater influence on overall and local thermal sensations and comfort than temperature gradient. Local thermal discomfort decreased with increase of room air temperature at overall thermally neutral state. The local discomfort was affected by overall thermal sensation and was lower at overall thermally neutral state than at overall cold and cool sensations.     

Variation of fracture toughness of asphalt concrete under low temperatures

This study presents the results of experimental evaluation on fracture toughness of asphalt concrete at various low temperatures (from −5°C to −30°C in 5°C steps). An asphalt cement, penetration grade of 85/100 and two aggregates, a granite and a limestone, were used to prepare asphalt concrete beam specimens which were conditioned using two different procedures and tested under three-point bending setup. The first procedure dealt with evaluation of fracture toughness of the asphalt concrete at a control temperature, −5°C, following conditioning at the specified temperatures. The second procedure dealt with evaluation of fracture toughness at the temperatures at which the samples were conditioned. The results showed that fracture toughness (K_IC) for both aggregate mixtures in both procedures changed in a manner that it increased by lowering temperature from −5°C to −15°C, and then decreased thereunder. An improved mechanical adhesion due to the strengthened grip of asphalt matrix resulted from differential thermal contraction (DTC) is responsible for increased resistance to the applied loads. The reduction of fracture toughness below −15°C is explained as the effect of internal damage due to DTC that is a consequence of the large difference in coefficients of thermal contraction between aggregate and asphalt cement. Granite aggregate mixture showed a slightly better resistance to fracture throughout the temperatures. Relatively good linear relations between average values of σ_f and K_IC were found from the regression analysis. Increasing flexural strength resulted in an increased fracture toughness for all mixtures. K_IC of granite mix showed more critical to the change of σ_f.     

Field study on occupants’ thermal comfort and residential thermal environment in a hot-humid climate of China

This paper discusses thermal comfort inside residences of three cities in the hot-humid climate of central southern China. Only a few thermal comfort studies have been performed in hot-humid climates and none in Central Southern China. Field sampling took place in the summers of 2003 and 2004 by obtaining 110 responses to a survey questionnaire and measuring environmental comfort variables in three rooms in each of 26 residences. The objectives are to measure and characterize occupant thermal perceptions in residences, compare observed and predicted percent of dissatisfied and discern differences between this study and similar studies performed in different climate zones. Average clothing insulation for seated subjects was 0.54 clo with 0.15 clo of chairs. Only 48.2% of the measured variables are within the ASHRAE Standard 55-1992 summer comfort zone, but approximately 87.3% of the occupants perceived their thermal conditions acceptable, for subjects adapt to prevailing conditions. The operative temperature denoting the thermal environment accepted by 90% of occupants is 22.0–25.9°. In the ASHRAE seven-point sensation scale, thermal neutral temperature occurs at 28.6°. Preferred temperature, mean temperature requested by respondents, is 22.8°. Results of this study can be used to design low energy consumption systems for occupant thermal comfort in central southern China.     

Toxicity of chlorine to juvenile spot, Leiostomus Xanthurus

The sensitivity of juvenile spot, Leiostomus xanthurus, to total residual chlorine (TRC) in flowing sea-water was investigated. Incipient LC₅₀ bioassays, histopathology, avoidance tests and the combined effect of thermal stress and TRC were used to assess sensitivity.

Estimated incipient LC₅₀ values were 0.12 mg 1⁻¹ TRC at 10°C and 0.06 mg 1⁻¹ TRC at 15°C. Histological examination of spot used in the incipient LC₅₀ bioassay at 15°C and sacrificed while alive indicated pseudobranch and gill damage occurred in individuals exposed to a measured TRC concentration of 1.57 mg 1⁻¹. Spot exposed to lower concentrations of TRC, 0.02 0.06 mg 1⁻¹ at 15°C and sacrificed alive showed no consistent tissue damage.

Spot demonstrated temperature dependent avoidance responses to TRC. At 10°C, a concentration of 0.18 mg 1⁻¹ was required for significant (X²; P < 0.05) avoidance; at 15 and 20°C, spot showed significant avoidance of TRC concentrations as low as 0.05 mg 1⁻¹.

Simultaneous exposure of spot to thermal stress (5, 10 or 13°C above the acclimation temperature of 15°C) at measured TRC concentrations of 0.05 0.07 and 0.34–0.52 mg 1⁻¹ demonstrated a significant, (Z²) with Yates correction, P < 0.05) increase in sensitivity to TRC with increased temperature and exposure times for some of the groups tested.     

People''s clothing behaviour according to external weather and indoor environment

In prehistoric times man wore furs of animals to protect himself from the cold. Successively over the centuries clothing has become also a tool to distinguish ourselves in society. Clothing has in addition an important impact on people's perception of the indoor environment.

Clothing behaviour has been analysed by investigating the external and indoor parameters that motivate people's choice of clothing. Based on two existing databases, two types of buildings have been investigated: air-conditioned and naturally ventilated (NV) buildings. The impact of outdoor temperature on people's clothing selection has been considered. The outdoor temperature at 6 a.m. seems to affect people's choice of clothes the most. Gender does not significantly affect the selection of clothing insulation.

Latitude has also been investigated and a good correlation has been found between clothing insulation and external temperature in the ranges 20°–40° and −20° to −40° for NV buildings.

Indoor air temperature does not seem to influence the clothing choice early in the morning but it does seem to influence the change of clothing during the day, if this is authorized, in workplaces in NV buildings. Such action can be termed “clothing adjustment” during the day.

Some computer simulations on a test reference year have been carried out for a typical air-conditioned office to analyse a person's comfort when wearing different clothes. It is possible to see that in air-conditioned buildings a variation of 0.1 clo is sufficient to change totally the comfort evaluation. It is evident that further studies are needed in this field.     

Field experiments on energy consumption and thermal comfort in the office environment controlled by occupants’ requirements from PC terminal

The thermal environment in an office is not always optimal from the viewpoint of energy-conservation and occupants’ comfort. The main reason is that air-conditioning systems are controlled without taking the occupants’ needs into account. In this study, we would like to propose a new system to control air-conditioning systems, lighting systems, etc. via occupants’ requests. This system collects occupants’ requests from their own personal computers and controls the air-conditioning system with logic that balances the needs of occupants and energy consumption. The control logic is referred to as “Logic for Building a Consensus” and can be adjusted according to operating strategies such as energy-saving or occupants’ satisfaction with their environment. Moreover, the variety of feedback motivates occupants to cooperate with energy-saving efforts.

An interactive system to use occupants’ requests for controlling the air-conditioning system and providing a variety of feedback was developed. A series of cooling experiments were conducted in an open-plan office where about 50 people worked. The results show that this interactive system could save 20% more energy compared with controlling an air-conditioning system at a constant 26 °C.     

Relating seismic velocities, thermal cracking and permeability in Mt. Etna and Iceland basalts

We report simultaneous laboratory measurements of seismic velocities and fluid permeability on lava flow basalt from Etna (Italy) and columnar basalt from Seljadur (Iceland). Measurements were made in a servo-controlled steady-state-flow permeameter at effective pressures from 5–80 MPa, during both increasing and decreasing pressure cycles. Selected samples were thermally stressed at temperatures up to 900 °C to induce thermal crack damage. Acoustic emission output was recorded throughout each thermal stressing experiment.

At low pressure (0–10 MPa), the P-wave velocity of the columnar Seljadur basalt was 5.4 km/s, while for the Etnean lava flow basalt it was only 3.0–3.5 km/s. On increasing the pressure to 80 MPa, the velocity of Etnean basalt increased by 45%–60%, whereas that of Seljadur basalt increased by less than 2%. Furthermore, the velocity of Seljadur basalt thermally stressed to 900 °C fell by about 2.0 km/s, whereas the decrease for Etnean basalt was negligible. A similar pattern was observed in the permeability data. Permeability of Etnean basalt fell from about 7.5×10⁻¹⁶ m² to about 1.5×10⁻¹⁶ m² over the pressure range 5–80 MPa, while that for Seljadur basalt varied little from its initial low value of 9×10⁻²¹ m². Again, thermal stressing significantly increased the permeability of Seljadur basalt, whilst having a negligible effect on the Etnean basalt. These results clearly indicate that the Etnean basalt contains a much higher level of crack damage than the Seljadur basalt, and hence can explain the low velocities (3–4 km/s) generally inferred from seismic tomography for the Mt. Etna volcanic edifice.     

Observations of upper-extremity skin temperature and corresponding overall-body thermal sensations and comfort

This paper explores how upper extremity skin temperatures correlate with overall-body thermal sensation. Skin temperature measurements of the finger, hand, and forearm might be useful in monitoring and predicting people's thermal state. Subjective perceptions of overall thermal sensation and comfort were collected by repeated surveys, for subjects in a range of test chamber temperatures. A positive temperature gradient (finger warmer than the forearm) of as much as 2 K was seen when subjects felt warm and hot, while a negative temperature gradient (finger colder than the forearm) as much as 8.5 K was seen for cool and cold subjects. A useful warm/cold boundary of 30 °C was found in finger temperature, for both steady state and transient conditions. When finger temperature was above 30 °C, or finger-forearm skin temperature gradient above 0 K, there was no cool discomfort. When finger temperature was below 30 °C, or the finger-forearm skin temperature gradient less than 0 K, cool discomfort was a possibility. Finger temperature and finger-forearm temperature gradient are very similar in their correlation to overall sensation. We also examine how overall sensation is affected by actively manipulating the hand's temperature.     

Thermal comfort, skin temperature distribution, and sensible heat loss distribution in the sitting posture in various asymmetric radiant fields

This study aimed at investigating the thermal comfort for the whole body as well as for certain local areas, skin temperatures, and sensible heat losses in various asymmetric radiant fields. Human subject experiments were conducted to assess the overall comfort sensation and local discomfort, and local skin temperatures were measured. Through thermal manikin experiments, we discovered a new method for the precise measurement of the local sensible heat loss in nonuniform thermal environments. The local sensible heat losses were measured by the use of a thermal manikin that had the same local skin temperatures as the human subjects. The experimental conditions consisted of the anterior–posterior, right–left, and up–down asymmetric thermal environments created by radiation panels. A total of 35 thermal environmental conditions were created ranging from 25.5 to 30.5 °C for air temperature, from 11.5 to 44.5 °C for surface temperature of radiation panels, from 40% RH to 50% RH for humidity, and less than 0.05 m/s for inlet air velocity to the climatic chamber. The local skin temperature changed depending on the environmental thermal nonuniformity, even if the mean skin temperature remained almost the same. It is essential to use the skin temperature distribution as well as mean skin temperature for expressing thermal comfort in nonuniform environments. The local sensible heat loss changed depending on the environmental thermal nonuniformity, even if the mean sensible heat loss remained almost the same. The relationship between the local skin temperature and local sensible heat loss cannot be depicted by a simple line; instead, it varies depending on the environmental thermal nonuniformity. The local heat discomfort in the head area was dependent on both the local skin temperature and local sensible heat loss. However, the local cold discomfort in the foot area was related only to the local skin temperature.     

Anaerobic biological treatment of phenol at 9.5-15 degrees C in an expanded granular sludge bed (EGSB)-based bioreactor

The aims of this study were to demonstrate the (1) feasibility of psychrophilic, or low-temperature, anaerobic digestion (PAD) of phenolic wastewaters at 10–15 °C; (2) economic attractiveness of PAD for the treatment of phenol as measured by daily biogas yields and (3) impact on bioreactor performance of phenol loading rates (PLRs) in excess of those previously documented (1.2 kg phenol m⁻³ d⁻¹). Two expanded granular sludge bed (EGSB)-based bioreactors, R1 and R2, were employed to mineralise a volatile fatty acid-based wastewater. R2 influent wastewater was supplemented with phenol at an initial concentration of 500 mg l⁻¹ (PLR, 1 kg m⁻³ d⁻¹). Reactor performance was measured by chemical oxygen demand (COD) removal efficiency, CH₄ composition of biogas and phenol removal (R2 only). Specific methanogenic activity, biodegradability and toxicity assays were employed to monitor the physiological capacity of reactor biomass samples. The applied PLR was increased to 2 kg m⁻³ d⁻¹ on day 147 and phenol removal by day 415 was 99% efficient, with 4 mg l⁻¹ present in R2 effluent. The operational temperature of R1 (control) and R2 was reduced by stepwise decrements from 15 °C through to a final operating temperature of 9.5 °C. COD removal efficiencies of c. 90% were recorded in both bioreactors at the conclusion of the trial (day 673), when the phenol concentration in R2 effluent was below 30 mg l⁻¹. Daily biogas yields were determined during the final (9.5 °C) operating period, when typical daily R2 CH₄ yields of c. 3.3 l CH₄ g⁻¹ COD_removed d⁻¹ were recorded. The rate of phenol depletion and methanation by R2 biomass by day 673 were 68 mg phenol g VSS⁻¹ d⁻¹ and 12–20 ml CH₄ g VSS⁻¹ d⁻¹, respectively.     

Thermal comfort and productivity - Evaluation of workplace environment in a task conditioned office

The environment of workplace in an office involved in creative work was evaluated in 2005 and 2006. The M Company has installed partition based task/ambient conditioning systems (TAC) and several environment-friendly systems, such as double-skin and thermal-storage structures. It was intended to investigate the influence of the worker's behavior and task conditioning on worker's thermal comfort and productivity. In this survey, immediate thermal environment and worker's behavior were measured, and occupants' surveys of thermal comfort and feeling of fatigue were conducted. We found that both activity level of occupant and exposed thermal environment is greatly different one by one. It is suggested that an increase in metabolic rate according to worker's behavior influenced on their thermal comfort. Based on the knowledge obtained from this investigation, needs for TAC are discussed.     

Comfort,perceived air quality,and work performance in a low-power task–ambient conditioning system

Zhang's thermal comfort model [Zhang H. Human thermal sensation and comfort in transient and non-uniform thermal environments, Ph.D. thesis, UC Berkeley; 2003. 415 pp.] predicts that the local comfort of feet, hands, and face predominates in determining a person's overall comfort in warm and cool conditions. We took advantage of this in designing a task–ambient conditioning (TAC) system that heats only the feet and hands, and cools only the hands and face, to provide comfort in a wide range of ambient environments. Per workstation, the TAC system uses less than 41 W for cooling and 59 W for heating. We tested the TAC system on 18 subjects in our environmental chamber, at temperatures representing a wide range of practical winter and summer conditions (18–30 °C). A total of 90 tests were done. We measured subjects' skin and core temperatures, obtained their subjective responses about thermal comfort, perceived air quality, and air movement preference. The subjects performed three different types of tasks to evaluate their productivity during the testing. The TAC system maintains good comfort levels across the entire temperature range tested. TAC did not significantly affect the task performance of the occupants compared to a neutral ambient condition. Whenever air motion was provided, perceived air quality was significantly improved, even if the air movement was re-circulated room air. In our tests, subjects found thermal environments acceptable even if they were judged slightly uncomfortable (−0.5). By reducing the amount of control normally needed in the overall building, the TAC system saves energy. Simulated annual heating and cooling energy savings with the TAC system are as much as 40%.     

Aerobic treatment of piggery waste

The operating characteristics of laboratory waste treatment systems were studied during the aerobic degradation of pig excrement at different loading rates and temperatures. The treatment systems were of two types: one was operated with floc formation and gravity separation of liquid and suspended solid effluents; and a second was operated without floc formation or separation of the effluent into liquid and solid fractions.

With an operating temperature of 15°C the parameters most affected by loading rate were (1) the concentrations of suspended solids and chemical oxygen demand in the liquid effluent; (2) the pH value of the mixed liquor; (3) nitrification; (4) the BOD of the supernatant from the mixed liquor; and (5) output of suspended solids as a percentage of input.

The concentrations of suspended solids and chemical oxygen demand in the liquid effluents were little affected by loading rates in the range 0·05-0·15 g SS g MLSS⁻¹ d⁻¹ (0·02-0·06 g BOD g MLSS⁻¹ d⁻¹) but increased with increasing loading rate in the range 0·15-0·30 (0·06-0·12 BOD). At loading rates below about 0·17 g SS g MLSS⁻¹ d⁻¹ (0·07 g BOD g MLSS⁻¹ d⁻¹) the mixed liquors were acidic, with pH values down to 5·2, whereas at loading rates above about 0·80 (0·32 BOD) they were alkaline, with pH values up to 8·9. At intermediate loading rates the mixed liquor pH value was more variable though in general the higher the loading rate the higher also the pH value of the mixed liquor. Acidic conditions in the mixed liquors were attributed to the occurrence of nitrification, while in the absence of nitrification the mixed liquors remained alkaline. The concentration of BOD₅ in the supernatant from the mixed liquors increased with increasing loading rate from about 35 mg 1⁻¹ at a loading rate of 0·17 g SS g MLSS⁻¹ d⁻¹ (0·07 g BOD g MLSS⁻¹ d⁻¹) to about 250 mg 1⁻¹ at a loading rate of 1·30 (0·52 BOD). The output of suspended solids from the treatment systems represented about 70 per cent of input suspended solids at loading rates of about 0·15 g SS g MLSS⁻¹ d⁻¹ (0·06 g BOD g MLSS⁻¹ d⁻¹) and increased to about 100 per cent at loading rates of 0·80 (0·32 BOD). Output of chemical oxygen demand was about 60 per cent of input at the lower loading rates and 80–90 per cent at the higher ones.

Operation of treatment units at temperatures of 5 and 10°C instead of 15°C had little effect on the efficiency of degradation at loading rates in the range 0·085-0·20 g SS g MLSS⁻¹ d⁻¹ (0·034-0·08 g BOD g MLSS⁻¹ d⁻¹), but nitrification was prevented at 5°C. At loading rates of 0·77 (0·31 BOD) and 1·46 (0·58 BOD) operation at 25°C appeared to increase the amount of degradation as compared with that achieved at 15°C.

The practical implications of the results and possible future approaches to the aerobic treatment of farm wastes are discussed.     

Additive model for thermal comfort generated by matrix experiment using orthogonal array

In addition to ensuring the thermal comfort of occupants, monitoring and controlling indoor thermal environments can reduce the energy consumed by air conditioning systems. This study develops an additive model for predicting thermal comfort with rapid and simple arithmetic calculations. The advantage of the additive model is its comprehensibility to administrators of air conditioning systems, who are unfamiliar with the PMV–PPD model but want to adjust an indoor environment to save energy without generating complaints of discomfort from occupants. In order to generate the additive model, a laboratory chamber experiment based on matrix experiment using orthogonal array, was performed. By applying the analysis of variance on observed thermal sensation votes and percentage of dissatisfaction, the factor effects of environmental variables that account for the additive model were determined. Additionally, the applicability of the PMV–PPD model in hot and humid climates is discussed in this study, based on experimental results.     

Testing of Localized Ventilation Systems in a New Controlled Environment Chamber

This paper describes tests of thermal comfort and air distribution performance of two relatively new occupant-controlled localized ventilation (also called task ventilation) systems. The first is a raisd-floor distribution system providing air through grilles in the floor panels, and the second is a desk-mounted unit supplying conditioned air at desktop level. The tests were performed in a new controlled environment chamber (CEC) having unique capabilities for detailed studies of space conditioning and thermal comfort in office environments. Measurements were made in a mockup of a typical partitioned open-plan office, and the resulting temperature and air velocity distributions are reported for a variety of system- and locally controlled conditions. Comfort model predictions are presented to describe the degree of environmental control and range of occupant comfort levels produced in the workstations. The results are also compared to those produced by a conventional ceiling supply system. The tests investigated the effects of supply volume, supply location, supply vent orientation, supply/return temperature difference, heat load density, and workstation size and layout. Temperature differences in the range of 1–2.5°C were observed between adjacent workstations, and local air velocities in the vicinity of outlets could exceed 3 m/s. Such wide-ranging values could violate existing comfort standards (ASHRAE, 1981; ISO, 1984), if strictly interpreted. However since these systems put the local thermal conditions within the workstations under the direct control of their occupants, it is recommended that the standards grant exceptions to such systems.     

The maturity method: Modifications to improve estimation of concrete strength at later ages

Two modifications have been proposed for the Nurse–Saul maturity function to get better estimates of compressive strength of concrete cured at different temperatures. The modifications account for the effect of w/c ratio on the temperature dependence of strength development and the effect of curing temperature on the long-term strength. The effect of the proposed modifications on the estimation of concrete strength using the Nurse–Saul maturity function have been compared with the estimation using unmodified Nurse–Saul equation with two different datum temperatures (i.e., T₀ = −10 °C and T₀ = 0 °C). The results show that applying the proposed modifications improves the accuracy of estimated concrete strength at different curing temperatures, especially at later ages.     

A study of the thermal comfort of primary school children in summer

A study of the thermal comfort and clothing of primary school children aged 7–9 took place during the summers of 1971 and 1972. Of the 641 children who took part, 262 produced records suitable for analysis. The weight of clothing followed the trend of room temperature over several days, but did not respond to diurnal changes of temperature. The subjective warmth followed the variations of room temperature, but was not related to the mean temperatures of the classrooms, which were between 17° and 23°. The children differed significantly among themselves in their subjective response to temperature, but there was no appreciable difference between the responses of the boys and the girls. Thermal comfort distributions are presented and their implications for classroom temperatures are discussed.     

国外工位空调系统研究进展

本文对当前国际上工位空调领域内的研究工作进行了回顾和总结,介绍了不同工位空调系统的构成形式,及其在提高工作区热舒适性及空气品质等方面的效果,提出了空调领域中一个新的发展模式,分析并指出了我国在该领域内研究和发展的方向。     

Thermal diary: Connecting temperature history to indoor comfort

To explore the relationship between thermal history and indoor comfort, surveys and measurements were conducted in Seoul, Korea and Yokohama, Japan. Fifty-two subjects were recruited from university campuses in Seoul and Yokohama during the hot season in August 2002. To collect information regarding people's daily thermal history, background questions (a thermal diary) were completed by subjects during the 24 h prior to entering in a climate chamber. Subjects changed into uniform clothing ensembles and complete thermal diary questions just prior to entering the chamber which was pre-conditioned to 28 °C and 50% relative humidity. Subjects entered the chamber and completed a set of thermal comfort questions at 10-min intervals for 1 h. Thermal history, prior to the chamber experiment, influenced the thermal sensation in chamber. Though the physical conditions in the climate chamber were identical (28 °C, 50% rh), Yokohama subjects responded with cooler thermal sensations than Seoul subjects. These subjects experienced hotter weather conditions (than the Seoul subjects) and voted that they felt cooler than the Seoul subjects who experienced cooler temperatures prior to entering the chamber. It was also found that subjects who use air-conditioning at home responded with warmer thermal sensations than the subjects who did not use air-conditioning. These results indicate that there is a strong interaction and influence of our experience with outdoor weather and our indoor thermal comfort.