Thermal sensation and comfort with different task conditioning systems

Subjective experiments with task conditioning systems, 3DU⁺, PEM, TU, and RCU were conducted to investigate the effect of three different types of Task air-conditioning systems on thermal comfort in a climate chamber. The chamber was conditioned at 28 °C/50%RH with task systems and 26 °C/50%RH without them. Under the condition with the task conditioning systems, the average rating of comfort sensation was between comfortable (0) and slightly uncomfortable (−1). For males it was between −0.5 and −0.7 and for females between −0.3 and −0.4. This was equal to or even better than that in condition without task system. It was found that these systems were effective in providing thermal comfort. The parts to which subjects wanted to diffuse air were different for each system. However, the individual control of task conditioning system contributed to create the preferred environment.     

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.     

Effects of 6‐h exposure to low relative humidity and low air pressure on body fluid loss and blood viscosity

The purpose of this study was to investigate the effects of 6‐h exposure to low relative humidity (RH) and low air pressure in a simulated air cabin environment on body fluid loss (BFL) and blood viscosity. Fourteen young healthy male subjects were exposed to four conditions, which combined RH (10% RH or 60% RH) and air pressure (NP: sea level or LP: equivalent to an altitude of 2000 m). Subjects remained seated on a chair in the chamber for 6 h. Their diet and water intake were restricted before and during the experiment. Insensible water loss (IWL) in LP10% condition was significantly greater than in NP60% condition; thus, combined 10%RH and LP conditions promoted a greater amount of IWL. The BFL under the LP condition was significantly greater than that under the NP condition. Blood viscosity significantly increased under LP conditions. Increases in red blood cell counts (RBCs) and BFL likely contributed to the increased blood viscosity. These findings suggest that hypobaric‐induced hypoxia, similar to the conditions in the air cabin environment, may cause increased blood viscosity and that the combined low humidity and hypobaric hypoxia conditions increase IWL.     

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.     

Intelligence in buildings: the potential of advanced modelling

“Intelligence” in buildings usually implies facilities management via building automation systems (BAS). However, present-day commercial BAS adopt a rudimentary approach to data handling, control and fault detection, and there is much scope for improvement. This paper describes a model-based technique for raising the level of sophistication at which BAS currently operate. Using stochastic multivariable identification, models are derived which describe the behaviour of air temperature and relative humidity in a full-scale office zone equipped with a dedicated heating, ventilating and air-conditioning (HVAC) plant. The models are of good quality, giving prediction accuracies of ±0.25 °C in 19.2 °C and of ±0.6% rh in 53% rh when forecasting up to 15 minutes ahead. For forecasts up to 3 days ahead, accuracies are ±0.65 °C and ±1.25% rh, respectively.

The utility of the models for facilities management is investigated. The “temperature model” was employed within a predictive on/off control strategy for the office zone, and was shown to substantially improve temperature regulation and to reduce energy consumption in comparison with conventional on/off control. Comparison of prediction accuracies for two different situations, that is, the office with and without furniture plus carpet, showed that some level of furnishing is essential during the commissioning phase if model-based control of relative humidity is contemplated.

The prospects are assessed for wide-scale replication of the model-based technique, and it is shown that deterministic simulation has potential to be used as a means of initialising a model structure and hence of selecting the sensors for a BAS for any building at the design stage. It is concluded that advanced model-based methods offer significant promise for improving BAS performance, and that proving trials in full-scale everyday situations are now needed prior to commercial development and installation.     

Calcination of Roman cement: A pilot study using cement-stones from Whitby

Roman cement was patented in 1796 and established as a major material in the development of European architecture and engineering in the 19th century. However, the market is poorly served for those conservators wishing to use authentic materials in their work and there is a need to reintroduce Roman cement for such purposes.

Cement-stones from Whitby were calcined at various temperatures and residence times in a laboratory kiln. The resulting cements were assessed for setting time, strength development and mineralogical characteristics.

The properties are sensitive to calcination conditions with optimum strengths being achieved at temperatures of approximately 900 °C accompanied by rapid setting of <1 min. A three stage strength development profile was identified characterised by a high initial strength, a dormant period which could last for many weeks and a final increase in strength to an age of 1 year.

Considerable variation in the composition was noted and related to the calcination conditions. Of particular interest is the formation of both ′-belite and β-belite under differing calcination conditions. Clinker particles were also compared using the SEM in both secondary electron and back-scattered electron imaging modes and the development of morphology observed.     

The long-term nutrient accumulation with respect to anthropogenic impacts in the sediments from two freshwater marshes (Xianghai Wetlands, Northeast China)

Sediment cores, representing a range of watershed characteristics and anthropogenic impacts, were collected from two freshwater marshes at the Xianghai wetlands (Ramsar site no. 548) in order to trace the historical variation of nutrient accumulation. Cores were ²¹⁰Pb- and ¹³⁷Cs-dated, and these data were used to calculate sedimentation rates and sediment accumulation rates. Ranges of dry mass accumulation rates and sedimentation rates were 0.27–0.96 g m⁻² yr⁻¹ and 0.27–0.90 cm yr⁻¹, respectively. The effect of human activities on increased sediment accumulation rates was observed. Nutrients (TOC, N, P, and S) in sediment were analyzed and nutrient concentration and accumulation were compared in two marshes with different hydrologic regime: an “open” marsh (E-0) and a partly “closed” marsh (F-0). Differences in physical and chemical characteristics between sediments of “open” and partly “closed” marsh were also observed. The “open” marsh sequestered much higher amounts of TOC (1.82%), N (981.1 mg kg⁻¹), P (212.17 mg kg⁻¹), and S (759.32 mg kg⁻¹) than partly “closed” marsh (TOC: 0.32%, N: 415.35 mg kg⁻¹, P: 139.64 mg kg⁻¹, and S: 624.45 mg kg⁻¹), and the “open” marsh indicated a rather large historical variability of TOC, N, P, and S inputs from alluvial deposits. Nutrient inputs (2.16–251.80 g TOC m⁻² yr⁻¹, 0.43–20.12 g N m⁻² yr⁻¹, 0.39–3.03 g P m⁻² yr⁻¹, 1.60–15.13 g S m⁻² yr⁻¹) into the Xianghai wetlands of China are in the high range compared with reported nutrient accumulation rates for freshwater marshes in USA. The vertical variation, particularly for N, P, and S indicated the input history of the nutrients of the Xianghai wetlands developed in three periods—before 1950s, 1950–1980s, and after 1980s. The ratios between anthropogenic and natural inputs showed that the relative anthropogenic inputs of TOC, N, P, and S have been severalfold (TOC: 1.68–11.21, N: 0.47–3.67, P: 0.24–1.36, and S: 1.46–2.96) greater than values of their natural inputs after 1980s. The result is probably attributable, in part, to two decades of surface coal mining activities, urban sewage, and agriculture runoff within the upstream region of the Huolin River. Our findings suggest that the degree of anthropogenic disturbance within the surrounding watershed regulates wetland sediment, TOC, N, P, and S accumulation.     

Wet and dry cured compressive strength of concrete containing ground granulated blast-furnace slag

This paper reports a part of an ongoing laboratory investigation in which the compressive strength of ground granulated blast-furnace slag (GGBFS) concrete studied under dry and wet curing conditions. In the study, a total of 45 concretes, including control normal Portland cement (NPC) concrete and GGBFS concrete, were produced with three different water-cement ratios (0.3, 0.4, 0.5), three different cement dosages (350, 400, 450 kg/m³) and four partial GGBFS replacement ratios (20%, 40%, 60%, 80%). A hyperplasticizer was used in concrete at various quantities to provide and keep a constant workability. Twelve cubic samples produced from fresh concrete were de-moulded after a day, then, six cubic samples were cured at 22±2 °C with 65% relative humidity (RH), and the remaining six cubic samples were cured at 22±2 °C with 100%RH until the samples were used for compressive strength measurement at 28 days and three months. Three cubic samples were used for each age and curing conditions. The comparison was made on the basis of compressive strength between GGBFS concrete and NPC concrete. GGBFS concretes were also compared within themselves. The comparisons showed that compressive strength of GGBFS concrete cured at 65%RH was influenced more than that of NPC concrete. It was found that the compressive strength of GGBFS concrete cured at 65%RH was, at average, 15% lower than that of GGBFS concrete cured at 100%RH. The increase in the water-cementitious materials ratios makes the concrete more sensitive to dry curing condition. The influence of dry curing conditions on GGBFS concrete was marked as the replacement ratio of GGBFS increased.     

Kinetic competition between phosphorus release and denitrification on sludge under anoxic condition

The kinetic behaviors of simultaneous phosphorus release and denitrification on sludge were investigated under anoxic condition. A phosphorus enriched sludge produced from Anaerobic-Anoxic-Oxic (AnAO) process under various SRT (5, 10 and 15 days) operation conditions was carried out in a series of batch tests. Experimental results indicated that the available organic substrate determined the kinetic behaviors of phosphorus release/uptake and denitrification. The simultaneous phosphorus release and denitrification demonstrated a kinetic competition under anoxic conditions in the presence of an available organic substrate. When the substrate was abundant, sludge was under “releasable-phosphorus-limited” condition; phosphorus release rate decreased slightly by nitrate inhibition. However, nitrate significantly inhibited phosphorus release when sludge was under “initial-substrate-limited” condition. Moreover, the sludge's phosphorus contents (as created by different SRT processes) dominated the kinetics of competition between phosphorus release and denitrification. The sludge with a high phosphorus content had a higher phosphorus release rate in accordance with a lower denitrification rate. Additionally, the substrate sequestrated rate markedly increased under the condition of simultaneous phosphorus release and denitrification. Finally, a preliminary metabolism model of denitrifying phosphorus removal bacteria was proposed, and found to be capable of adequately accounting for simultaneous phosphorus release and denitrification under anoxic conditions.     

Filtration methods for recovery of Bacillus anthracis spores spiked into source and finished water

Spores of Bacillus anthracis Sterne strain were recovered from 100 ml and 1 L volumes of tap and source waters using filtration through a 0.45 um filter, followed by overnight culture on agar plates. In a set of experiments comparing sheep red blood cell (SRBC) plates with a chromogenic agar formulation designed by R & F Laboratories, with a spiking dose of 47 plate-enumerated spores in 100 ml tap water, the mean spore recoveries were 34.0 and 30.8 spores, respectively. When a spiking dose of 100 fluorescence activated cell sorter(FACS)-enumerated spores was used in 100 ml potable water, the average recovery with SRBC plates was 48 spores. Detection efforts with spiking doses of 35 and 10 spores in 1 L tap water were successful, but recovery efforts from spiked 1 L volumes of source water were problematic due to the concomitant growth of normal spore-forming flora. Recoveries were also attempted on 10 L volumes of tap water. For a spiking dose of 100 spores, mean recovery from six replicates was 11 spores (±6.8, range 2–20), and for a spiking dose of 10 spores, mean recovery from six replicates was 2.3 spores (±3.5, range 0–9). Efforts were also made to “direct detect” spores via polymerase chain reaction (PCR) on washes from filters. When spiking 534 spores in 100 ml, 9/9 replicates of spiked tap water, 6/6 source water replicates, and 0/3 unspiked controls were positive by lef PCR. When 534 spores were spiked into 1 L tap water, the lef PCR was unsuccessful; however, using the nested vrrA PCR resulted in 4/9 spiked samples, and 0/3 unspiked controls, testing positive. Our results indicate that an inexpensive and user-friendly method, utilizing filtration apparatus commonly present in many water quality testing labs, can readily be adapted for use in detecting this potential threat agent.     

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.     

The effects of free chlorine and chloramine on growth and respiration rates of larval lobsters (Homarus Americanus)

The length, dry weight and standard respiration rate of larval lobsters (Homarus americanus) were monitored for 19 days following a 60 min exposure at 25°C to 1.0 mg I⁻¹ applied free chlorine and 1.0 mg I⁻¹ applied chloramine. Compared to control organisms, significantly lower increases in dry weight (P < 0.05) and significant reductions in standard respiration rates (P < 0.01) were measured among exposed organisms; greater differences were detected among chloramine exposed organisms. From these results it can be concluded that acute exposure to either free chlorine or chloramine results in subsequent reductions in growth and metabolic activity of larval lobsters.     

A planktonic Oscillatoria species from Mississippi catfish ponds that produces the off-flavor compound 2-methylisoborneol

A planktonic, gas-vacuolate Oscillatoria species was isolated from catfish ponds in Mississippi during an episode of off-flavor and high 2-methylisoborneol (MIB) levels. Volatile compounds from unialgal cultures were isolated using closed-loop stripping, liquid-liquid extraction, and analyzed by gas chromatography and mass spectroscopy. The organism produced MIB at 75–87 μg 1⁻¹ after 2–3 wk of incubation at 25°C. The alga was found in moderate to high numbers in three pond water samples with high MIB levels, and low numbers in two other samples with low MIB levels. The organism was not present (less than one organism/10 ml) in nine other samples characterized by a “woody” or “swampy” odor and no detectable MIB. This Oscillatoria strain is believed to be the first blue-green alga that produces MIB ever isolated from Mississippi catfish ponds, and may be a cause of the off-flavor problem associated with MIB in those systems.     

Foams and gels as fire protection agents

Fire protection foams and gels are used as temporary barriers to protect samples from incident thermal radiation thus delaying their ignition. Comparative measurements of the thermal behavior of these agents are made using a radiant heat exposure. The results of this comparison clearly show that thermal protection is obtained by two different mechanisms. The conduction-dominated gel operates at near saturation conditions (100°C). The radiation-dominated foam provides complete protection at ambient conditions (20–30°C) for about half the transient duration. Thereafter, the residual foam layer cannot prevent a rapid heat-up of the sample. Tests are performed applying the agents to a flat sample that is then positioned vertically and exposed to radiant heat. The lateral ignition and flame spread test (LIFT) apparatus is used to determine the ignition delay time for the gel. Due to the sample size restrictions associated with the LIFT apparatus, data collection for foams is not possible. Therefore, measurements are conducted in a Radiant Exposure Apparatus (REA) which allows for larger samples subjected to uniform heat fluxes up to 18 kW/m². The data gathered from the LIFT and REA are compared to establish the consistency between the two measurement sets.     

Influence of dry and wet curing conditions on compressive strength of silica fume concrete

This paper reports a part of an ongoing laboratory investigation in which the compressive strength of silica fume concrete is studied under dry and wet curing conditions. In the study, a total of 48 concretes, including control Portland cement concrete and silica fume concrete, were produced with four different water–cement ratios (0.3, 0.4, 0.5, 0.6), three different cement dosages (350, 400, 450 kg/m³) and three partial silica fume replacement ratios (10%, 15%, 20%). A hyperplastisizer was used in concrete at various quantities to provide and keep a constant workability. Three cubic samples produced from fresh concrete were demoulded after a day; then, they were cured at 20±2 °C with 65% relative humidity (RH), and three other cubic samples were cured at 20±2 °C with 100% RH until the samples were used for compressive strength measurement at 28 days. The comparison was made on the basis of compressive strength between silica fume concrete and control Portland cement concrete. Silica fume concretes were also compared among themselves. The comparisons showed that compressive strength of silica fume concrete cured at 65% RH was influenced more than that of Portland cement concrete. It was found that the compressive strength of silica fume concrete cured at 65% RH was, at average, 13% lower than that of silica fume concrete cured at 100% RH. The increase in the water–cementitious material ratios makes the concrete more sensitive to dry curing conditions. The influence of dry curing conditions on silica fume concrete was marked as the replacement ratio of silica fume increased.     

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.     

An experimental study of relative humidity effect on VOCs’ effective diffusion coefficient and partition coefficient in a porous medium

Most building materials are porous media. As a critical environmental factor, the influence of relative humidity on VOCs diffusion is still not well understood. In this study, VOC transport and sorption in a porous medium in the building materials (calcium silicate) were measured under three levels of relative humidity (25%, 50% and 80%) by using a dynamic dual chamber method. Tests were conducted for water-soluble compound (formaldehyde) and non-soluble compound (toluene). In addition, the transport of acetaldehyde, hexanal, benzaldehyde, butanol and decane through the calcium silicate were also tested at 50%RH to study the relationship between the effective diffusion coefficient (D_e), partition coefficient (K_ma) and the VOCs’ physical properties (molecular weight, vapor pressure and Henry’s law constant). Experimental results showed that: relative humidity in the 80%RH led to a higher partition coefficient for formaldehyde compared to 50%RH. However, between 25% and 50%RH, there was no significant difference in partition coefficient. Partition coefficient of toluene decreased with the increase of humidity due to competition of water molecules for pore surface area and the non-solubility nature of toluene. Relative humidity had no significant influence on the effective diffusion coefficient on both formaldehyde and toluene for the range of moisture conditions tested. The solubility of VOCs was found to correlate with the partition coefficient of VOCs. The partition coefficient of VOCs was not simply inversely proportional to the vapor pressure of the compound, but also increased with the increase of Henry’s law constant.     

Thermal performance of a personalized ventilation air terminal device at two different turbulence intensities

The performance of a circular perforated panel (CPP) air terminal device for a personalized ventilation (PV) system operating under two levels of turbulent intensity (Tu) was examined. The impact of Tu on spatial distribution of the cooling effect on the facial region and whole body were studied through experiments carried out in an indoor environment chamber using a breathing thermal manikin and 24 tropically acclimatized subjects. The PV system was adjusted to deliver treated outdoor air over a range of conditions, which were presented blind to the subjects in a balanced order. Over a 15-min exposure, subjects voted their thermal sensation experienced at the facial region and whole body. At each of the conditions, the near body flow field characteristics and heat loss rate on each of the 26 body segments of the manikin were measured. The results indicate that over the range of PV air supply volume studied, by controlling the temperature and velocity of PV air supply at 15 cm from the face, PV air supplied at lower Tu, when compared against that supplied at higher Tu:

• Achieved a larger range of velocities at the face.

• Achieved a greater cooling effect on the head region.

• Achieved a lower facial thermal sensation, which has potential draft risks (when facial_thermal sensation vote <−1).

Denitrification with natural gas and various new growth media

Biological denitrification was investigated in an attached growth reactor system using several growth media, denitrifying cultures and natural gas (95% methane) as a carbon source. In order to establish a baseline of operation, initial experiments were conducted with a bed of 2–3 mm sand and methanol as a carbon source using a methylotrophic denitrifying culture and then the system was compared with natural gas using various methane utilising cultures. Compared to methanol, performance with methane was considerably lower. In order to improve denitrification with methane a plastic medium (Etapak, surface area 200 m²/m³) was placed above the sand bed (which increased the surface area for bacteria growth in the upper part of the bed), and a new methanotrophic mixed culture (NCIMB-code 11085) was introduced to the system. This combination resulted in a 27% higher denitrification efficiency. Experiments were continued by systematically varying the operating conditions to obtain highest denitrification using methane gas and replacing the Etapak media with different plastic media of higher surface area, but keeping the NCIMB culture unchanged. Other media tested were Pall-rings (surface area 319 m²/m³), IP-spacers (surface area 500 m²/m³) and granular activated carbon (GAC-code: Norit PK 1–3). Best results were obtained with IP-spacers which, surprisingly, are designed for use in the concrete industry rather than as a bacterial support medium. These produced nitrate removal efficiencies of up to 93% at 0.6 m/h or 55% at 1.6 m/h water filtration rates. Run times of 10 days or more to a limiting headloss of about 1.0 m,were usually achieved before “bumping” or back-washing to reduce headloss. Effluent turbidities were generally below 1.0 NTU. Tests for bacteria present with GAC media and COD removal with IP spacers were also carried out. Results are discussed with operational conditions and denitrification efficiencies achieved.     

Thermal comfort study of young Chinese people in Hong Kong

The purpose of this study is to investigate the thermal comfort of college-age Chinese subjects and obtain the optimum thermal conditions for buildings. 134 college-age Chinese subjects wearing 0.6 clo standard clothing were exposed under sedentary activity for 3 h to several different thermal conditions. The neutral temperature of young Hong Kong Chinese was found to be 24.9°C. This is not significantly different from previous studies with Danish and American subjects. Using the probit technique for analysing subjective responses of thermal sensation the neutral zone was found to be between 22.2 and 25.2°C.