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Development of JOS-2 Human Thermoregulation Model with Detailed Vascular System

April 26, 2013, 8:19 am
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Publication date: Available online 26 April 2013
Source:Building and Environment
Author(s): Yutaka Kobayashi , Shin-ichi Tanabe
A human thermoregulation model called JOS-2 was developed based on the Stolwijk model and our previously developed (in 2002) JOS model. In this model, the whole body was idealized as 17 spherical or cylindrical body segments (Head, Neck, Chest, Pelvis, right and left Shoulders, right and left Arms, right and left Hands, right and left Thighs, right and left Legs, and right and left Feet). The Head segment consists of four layers—core, first layer, second layer, and skin—and the other segments consist of two layers—core and skin). All body segments have artery and vein blood pools. In addition, the limb segments have a detailed vascular system consisting of superficial veins and arteriovenous anastomoses (AVA). Thermoregulatory mechanisms such as vasoconstriction, vasodilation, perspiration, and shivering are considered. The physical parameters of this model, such as height, weight, sex, age, body fat percentage, basal metabolic rate, and cardiac index, can be changed. This paper describes the equations and coefficients as well as the model validation for stable, nonuniform, transient conditions.

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Evaluation of Thermal Environmental Conditions and Thermal Perception at Naturally Ventilated Hostels of Undergraduate Students in Composite Climate

April 27, 2013, 8:54 am
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Publication date: Available online 27 April 2013
Source:Building and Environment
Author(s): Shivraj Dhaka , Jyotirmay Mathur , Andreas Wagnerb , Ghanshyam Das Agrawal , Vishal Garg
Field study of thermal comfort was conducted in six naturally ventilated hostel buildings of composite climate considering Class-II protocol of field measurement during summer 2011. Total 429 survey samples of same age group (average 19.6 years) were collected including objective and subjective measurements. Statistical analysis of student’s responses and measured thermal environmental variables was performed to determine existing indoor environmental conditions and priority of using behavioural controls. Thermal comfort indices were also calculated and compared to the student’s perceptions. Neutral temperature was found to be 30.15oC through regression analysis, with an average clothing of 0.41 Clo (min. 0.19 Clo, max 0.82 Clo). Results have shown a wide bandwidth of neutral temperatures (25.9oC to 33.8oC) for the hostel buildings which is higher than national/international standards of thermal comfort. Acceptable air velocity and relative humidity were found to be 0.51m/s and 36%, respectively. Analysis has shown that about 51% students felt ‘overall comfortable’ at the existing environmental conditions in the hostel rooms and only 38% occupants were comfortable based on room air temperature. Students from single, double and triple occupancy rooms were found thermally satisfied at neutral temperature of 30.4°C, 30.1°C and 29.8oC, respectively and their thermal preferences were different.

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Optimization of design flow rates and component sizing for residential ventilation

April 27, 2013, 8:54 am
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Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): J. Laverge , A. Janssens
The potential systemic differences in performance of natural, exhaust and mechanical ventilation in dwellings is the object of relentless debate among scientists, industry and policy makers, although comparisons found in literature often fail to compare the different systems on an equal basis. Presenting the results from a multi zone simulation based optimization study of residential ventilation design flow rates and sizing of the system components, this paper aims to provide a benchmark for achievable performance for the different systems for moderate climate regions (eg. Western Europe), as well as point to possible sizing strategies for future standards. The results clearly demonstrate that, considering average occupant exposure to metabolic carbon dioxide, there are small differences in the optimal performance for the 3 system approaches, with an increase of about 13% in ventilation heat loss for equal exposure for the natural ventilation system compared to the mechanical ventilation system. These differences are more marked (up to 26%) when peak exposure is considered. For typically household activity related sources, the mechanical and exhaust ventilation systems provide substantially better optimal performance, while building tighter improved the performance of all 3 system approaches. Exhaust ventilation benefits from small trickle ventilators and large transfer devices. The latter also improves the performance of natural ventilation systems, while slightly higher supply flow rates provide the best results for mechanical ventilation.

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Assessing the stability of annual temperatures for different urban functional zones

April 28, 2013, 8:58 am
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Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): Ranhao Sun , Yihe Lü , Liding Chen , Liu Yang , Ailian Chen
The urban functional zone (UFZ) is the basic unit of urban planning, which is defined as an area of similar social and economic functions. Despite the importance of UFZs, the stability of their annual temperature between winter and summer has seldom been investigated. With an understanding of the thermal impacts that planning decisions can have, it is essential to know how UFZs can be designed to regulate temperatures in the urban environment. 690 UFZs were identified using ALOS images in 2009 in Beijing. Land surface temperature (LST) was extracted from daytime Landsat TM (2002) and ASTER (2009) images. The regional LST variation of 31 district-sized sub-regions was correlated to the types of UFZs in the region and structural features of the region such as area, size, diversity, complexity and connectivity. Results showed that: (1) UFZ types, in order from highest to lowest LST variation, were commercial, campus, high density residential, water, recreational, low density residential, road, preservation, and agricultural zones; (2) the regional LST variation was positively correlated with the area of campus, commercial, high density residential, water, and road zones, but negatively correlated with the area of agricultural and low density residential zones; (3) increased connectivity and complexity decreased regional LST variations. The results indicated that the stability of annual temperatures was determined not only by the UFZ type and size but also by the connectivity and complexity. These results are clearly useful and essential pieces of information that can be applied in urban planning to improve climate adaptability.

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Directions in green roof research: a bibliometric study

April 29, 2013, 9:25 am
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Publication date: Available online 29 April 2013
Source:Building and Environment
Author(s): Lior Blank , Amiel Vasl , Shay Levy , Gary Grant , Gyongyver Kadas , Amots Dafni , Leon Blaustein
Green roof research is a multidisciplinary and new research area. We conducted a bibliometric quantification to assess the rate of publications in specific areas of research for this novel research area based on the scientific literature as available from the Web of Science. Bibliometric research can provide valuable information about changes in the trends within a particular area of research. For example, we found that the number of publications in this field increased in the last two decades at very similar pace to other pre-established academic disciplines. We also found that papers on green roofs were classified into 32 research areas. There was very little change in the frequency of most research areas through time. The percentages of plant sciences, forestry, marine and freshwater biology and biodiversity conservation of the total research areas classifications used each year increased significantly with time, while architecture decreased significantly with time signifying an increased interest in environmental issues and less focus on architectural issues. The distribution of publications between countries has been skewed, with the USA and the EU conducting 66% of the research, and thus allocation of research effort is focused in those continents and predominantly in temperate ecosystems. However, there has been a sharp increase in the number of countries that conduct green roof research. Our work provides a suite of indicators that can be combined to give a useful picture of the development of green roof research and identifies the challenges which lie ahead for this novel research area.

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Computational investigation on the factors influencing thermal comfort for impinging jet ventilation

April 29, 2013, 9:25 am
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Publication date: Available online 29 April 2013
Source:Building and Environment
Author(s): Huijuan Chen , Bahram Moshfegh , Mathias Cehlin
Impinging jet ventilation (IJV) has been proposed to achieve an effective ventilation of an occupied zone in office and industrial buildings. For IJV systems, draught discomfort is the issue of most concern since it supplies cooled air directly to the occupied zone. This study investigated a number of factors influencing draught discomfort and temperature stratification in an office environment equipped with IJV. The factors considered were: shape of air supply device, discharge height, supply airflow rate and supply air temperature. The Response Surface Methodology (RSM) was used to identify the level of the significance of the parameters studied, as well as to develop the predictive models for the local thermal discomfort. Computational fluid dynamics (CFD) was employed to perform a set of required studies, and each simulation condition was determined by the Box-Behnken design (BBD) method. The results indicated that at a low discharge height, the shape of air supply device had a major impact on the flow pattern in the vicinity of the supply device because of the footprint from impinging jet, which consequently affected the draught risk level in the occupied zone. A square-shaped air supply device was found to result in lower overall draught discomfort than rectangular and semi-elliptic shapes. The RSM analysis revealed that the supply airflow rate had a significant impact on the draught discomfort, while the shape of air supply device and discharge height had moderate effects. The temperature stratification in the occupied zone was mostly influenced by the supply air temperature within the range studied.

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Multiplexed optimization for complex air conditioning systems

April 29, 2013, 9:25 am
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Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): Yongjun Sun , Gongsheng Huang , Zhengwei Li , Shengwei Wang
Optimization has been considered as an efficient tool to realize energy efficiency in the operation of air conditioning (AC) systems. With the increase of complexity of AC systems, the computational complexity of real-time optimization appears to be a challenge for practical applications. In order to overcome the challenge, this paper proposes a multiplexed optimization scheme. Unlike conventional optimization that optimizes and updates all decision variables simultaneously, the proposed scheme optimizes and updates the decision variables sequentially and one decision variable at a time. The proposed scheme is compared with a conventional optimization method (in which the genetic algorithm is adopted) as regards computational load, energy performance and system stability. Case studies show that compared with the conventional optimization method, the computational burden of the proposed scheme is greatly reduced, up to 98.3%; the energy saving achieved by the proposed scheme is 6.8%, which is comparable to that achieved by the conventional method (6.7%); and the system operation stability is significantly enhanced since the average tracking errors for several monitored variables were reduced around 50%.

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Comfort under personally controlled air movement in warm and humid environments

April 30, 2013, 9:58 am
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Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): Yongchao Zhai , Hui Zhang , Yufeng Zhang , Wilmer Pasut , Edward Arens , Qinglin Meng
This study examined the effects of personally controlled air movement on human thermal comfort and perceived air quality (PAQ) in warm-humid environments. At temperatures 26, 28, and 30 °C, and relative humidity (RH) 60% and 80%, sixteen human subjects were exposed to personally controlled air movement provided by floor fans in an environmental chamber. The subjects reported their thermal sensation, thermal comfort, and PAQ during the tests. Two breaks periods with elevated metabolic levels were used to simulate normal office activities. Results show that with personally controlled air movement, thermal comfort could be maintained up to 30 °C and 60% RH, and acceptable PAQ could be maintained up to 30 °C 80% RH, without discomfort from humidity, air movement or eye-dryness. Thermal comfort and PAQ were resumed within 5 min after the breaks. The 80% acceptable limit implicit in comfort standards could be extended to 30 °C and 60% RH. The average energy consumed by the fans for maintaining comfort was lower than 10 W per person, making air movement a very energy-efficient way to deliver comfort in warm-humid environments.

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Identification of key plant traits contributing to the cooling effects of green façades using freestanding walls

May 3, 2013, 10:49 am
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Publication date: Available online 2 May 2013
Source:Building and Environment
Author(s): Takuya Koyama , Mika Yoshinaga , Hideki Hayashi , Kei-ichiro Maeda , Akira Yamauchi
Green façades have long been used to reduce the overheating of buildings by excessive solar gain, but little research attention has been paid to the plant traits that reduce the surface temperature of urban structures. This study aimed to identify the key traits contributing to the cooling effects of green façades by comparing five vine plant species. The vines were trained to climb a plastic net that was attached on the freestanding walls under outdoor conditions. One of the walls was not covered with plants to serve as control. We measured the longest vine length, total number of leaves, percentage coverage, leaf transpiration rate, leaf solar transmittance, wall surface temperatures, global solar radiation on a vertical south surface (GSR) and ambient temperature. We identified the percentage coverage as the key trait determining the overall cooling effect: a statistically positive relationship (P < 0.001) was identified between the percentage coverage and the wall surface temperature reduction (WTR; the wall surface temperature differences between the non-covered wall and the covered wall) under GSR of more than 0.1 kW m-2. The percentage coverage was in turn found to be determined by the vine length. We also found that genotypic differences in WTRs that were not explained by those in the percentage coverage were related to those in leaf solar transmittance, indicating that this trait also contributed to the cooling effects.

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Passive alternatives to mechanical air conditioning of building: A review

May 3, 2013, 10:49 am
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Publication date: Available online 2 May 2013
Source:Building and Environment
Author(s): D.G. Leo Samuel , S.M. Shiva Nagendra , M.P. Maiya
Human comfort is gaining importance in the recent decades. Mechanical air conditioners are conventional means of creating thermal comfort but they are energy intensive and hence harmful to ecological system. Therefore passive cooling can be adopted as a viable alternative to conventional cooling system. This paper reviews various passive cooling options available such as nocturnal radiation, geothermal, ventilation, evaporative, hydrogeothermal, deep ocean/lake, thermal insulation and shading along with their advantages, limitations, working principles and climatic dependence. The mathematical equations used for computing the performance of passive cooling systems have been discussed along with design and environmental parameters influencing the systems’ performance. The usefulness of phase change materials, thermal mass and radiant cooling in passive cooling systems is also examined. Case studies containing experimental data and numerical predictions are discussed to provide options for building architects and infrastructure developers to adopt the appropriate passive cooling strategy. In addition, issues related to occupants’ health and indoor air quality are also explained. A brief review of energy-efficient and eco-friendly solar cooling systems is also included.

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Experimental study of a non-isothermal wall jet issued by a displacement ventilation system

May 3, 2013, 10:49 am
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Publication date: Available online 2 May 2013
Source:Building and Environment
Author(s): Iman Fatemi , Bing-Chen Wang , Mike Koupriyanov , Brad Tully
This paper reports a new set of experimental data and presents an in-depth analysis of the flow physics of a non-isothermal jet stream produced by a large quarter-round corner-mounted displacement diffuser. The air velocity, temperature and turbulence intensity inside the displacement ventilation (DV) jet have been thoroughly analyzed and compared with the reported findings of previous studies and model predictions. Through the experiment, it is observed that the DV jet development is significantly altered by buoyant forces and can be divided into four distinctive zones. The results of the present study refine the physical understanding of the coupled thermal-fluid fields characteristic of a DV jet stream, and are useful for improving the design of the DV system tested.

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CFD simulation of micro-scale pollutant dispersion in the built environment

May 3, 2013, 10:49 am
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Publication date: June 2013
Source:Building and Environment, Volume 64
Author(s): B. Blocken , Y. Tominaga , T. Stathopoulos


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Thermal comfort in buildings with split air-conditioners in hot-humid area of China

May 3, 2013, 10:49 am
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Publication date: June 2013
Source:Building and Environment, Volume 64
Author(s): Yufeng Zhang , Huimei Chen , Qinglin Meng
Occupants' thermal sensations, perceptions and behaviors in buildings with split air-conditioners in hot-humid area of China were systematically investigated for a whole year with longitudinal design. Thirty college students, naturally acclimatized to local climate and well experienced with the indoor environments of buildings, participated in the present study. They reported their thermal sensations, perceptions and behaviors in questionnaires while their ambient environmental variables were measured. A close match of indoor and outdoor climate was found. Thermal sensation was found to be a linear function of ET* or SET and thermal neutrality was 25.6 °C in ET* or 24.9 °C in SET. The central five categories of the ASHRAE 9-point thermal sensation scale were found to be acceptable and the 90% (80%) acceptable range of thermal environment was found to be 20.6–30.5 °C (16.9–34.2 °C) in ET*. The adaptive behaviors of clothing adjustment, opening windows and using fans were found to be closely correlated with indoor ET*. The split air-conditioners were used from May to October and turned on most often at midnight with indoor air temperature of 30.1 °C and setting temperature of 26.1 °C. Compared with those from naturally ventilated buildings, the occupants from buildings with split air-conditioners kept indoor climates much cooler, used adaptive opportunities much earlier and perceived their ambient environments more sensitively and rigidly.

Highlights

► Field study was conducted in buildings with split air-conditioners for a whole year. ► Thermal neutrality was 25.6 °C in ET* or 24.9 °C in SET. ► The 80% acceptable range of thermal environment was 16.9–34.2 °C in ET*. ► The central five categories of thermal sensation scale were found to be acceptable. ► Relationships between various behaviors and thermal environments were obtained.
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Atmospheric environmental impact assessment of a combined district heating system

May 3, 2013, 10:49 am
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Publication date: June 2013
Source:Building and Environment, Volume 64
Author(s): Wang Haichao , Jiao Wenling , Risto Lahdelma , Zou Pinghua , Zhan Shuhui
Assessing the atmospheric environmental impacts of district heating (DH) systems is of increasing importance as the environmental concerns and the eco-sustainability concept is more and more widespread in the energy sector around the world. However, this issue has been overlooked to some extent for past decades in China, which led to inappropriate assessments only by measuring pollutant emissions per unit floor area or unit heat supply. In this paper, we present an atmospheric environmental assessment model incorporating the state of the art AERMOD modeling and the concept of normalized population distribution weights (NPDWs) to compute the mean spatial distribution (MSD) of pollutants for qualitatively evaluating the atmospheric environmental impacts of DH. We demonstrate the model in assessing different heating scenarios, characterized by basic heat load ratio in a real-life combined district heating system of Daqing city with a population of 2.7 million. The results show that the presented model and MSD concentrations furnish a better base to assess the atmospheric environmental impact. We also show how the combined district heating system can undertake a part of CO2 emission reduction burden in the DH sector at a city-scale.

Highlights

► Atmospheric environmental impact of a combined heating system is studied. ► An assessment model based on AERMOD is proposed. ► Population distribution is taken into account in the model. ► Mean spatial distribution of pollutants are proposed to measure the impact. ► Combined heating systems using gas-fired boilers are environmentally efficient.
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Editorial Board

May 3, 2013, 10:49 am
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Publication date: June 2013
Source:Building and Environment, Volume 64



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Coupled TRNSYS-CFD simulations evaluating the performance of PCM plate heat exchangers in an airport terminal building displacement conditioning system

May 3, 2013, 10:49 am
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Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): B.L. Gowreesunker , S.A. Tassou , M. Kolokotroni
This paper reports on the energy performance evaluation of a displacement ventilation (DV) system in an airport departure hall, with a conventional DV diffuser and a diffuser retrofitted with a phase change material storage heat exchanger (PCM-HX). A TRNSYS-CFD quasi-dynamic coupled simulation method was employed for the analysis, whereby TRNSYS® simulates the HVAC and PID control system and ANSYS FLUENT® is used to simulate the airflow inside the airport terminal space. The PCM-HX is also simulated in CFD, and is integrated into the overall model as a secondary coupled component in the TRNSYS interface. Different night charging strategies of the PCM-HX were investigated and compared with the conventional DV diffuser. The results show that: i) the displacement ventilation system is more efficient for cooling than heating a space; ii) the addition of a PCM-HX system reduces the heating energy requirements during the intermediate and summer periods for specific night charging strategies, whereas winter heating energy remains unaffected; iii) the PCM-HX reduces cooling energy requirements, and; iv) maximum energy savings of 34% are possible with the deployment of PCM-HX retrofitted DV diffuser.

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Evaluation of various categories of turbulence models for predicting air distribution in an airliner cabin

May 3, 2013, 10:49 am
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Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): Wei Liu , Jizhou Wen , Chao-Hsin Lin , Junjie Liu , Zhengwei Long , Qingyan Chen
Flow fields in commercial airliner cabins are crucial for creating a thermally comfortable and healthy cabin environment. The study of flow fields in cabins could be achieved by numerically solving Navier–Stokes equations with a suitable turbulence model. This investigation evaluated three turbulence models in different categories: the RNG k-ε model, LES, and DES for the steady-state flow in the first-class cabin of a functional MD-82 commercial airliner. The measured flow fields under unoccupied and fully-occupied conditions in the first-class cabin were used for validating the turbulence models. The flow in the unoccupied cabin was isothermally forced convection created by air jets from the diffusers, while the flow in the fully-occupied cabin was mixed convection driven by both the jets and thermal plumes from the thermal manikins used to simulate passengers. This study found that the RNG k-ε model gave acceptable accuracy in predicting the airflow in the unoccupied cabin where the flow was simple, but not for the complicated flow in the fully-occupied cabin. The DES gave acceptable flow fields for both cabins. The LES performed the best and the results agreed well with the experimental data. Comparing the measured flow fields in the two cabin conditions, this study found that the thermal plumes from the heated manikins had a significant influence on the flow fields, but little influence on the turbulence.

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Impact of Design Parameters on the Performance of Ultraviolet Photocatalytic Oxidation Air Cleaner

May 4, 2013, 5:22 pm
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Publication date: Available online 4 May 2013
Source:Building and Environment
Author(s): Donya Farhanian , Fariborz Haghighat , Chang-Seo Lee , Ness Lakdawala
Ultraviolet photocatalytic oxidation (UV-PCO) is regarded as one of the promising technologies for air purification. Previous studies on UV-PCO of ethanol were performed in an ideal bench top reactors. However, this research is focused on UV-PCO of ethanol in full-scale open test rig which closely resembles the real application of this technology. Ethanol mineralization was investigated under several conditions including two types of UV-lamps (UVC and VUV) for two different photocatalysts under varied concentrations, airflow rate and relative humidity. In each case, removal efficiency and by-products yield were compared. Furthermore, possible mechanism for by-product formation is presented. Experimental results show that acetaldehyde and formaldehyde are the main by-products of ethanol. VUV lamps increase photocatalytic oxidation of ethanol compared to UVC lamps. The increase of relative humidity decreases UV-PCO of ethanol using both VUV and UVC lamps; however, the yield of by-products in the presence of VUV lamps increases while it decreases in the presence of UVC lamps. Higher flow rate results lower removal efficiency and consequently formation of less by-products. Improvement of reaction section by increasing the number of reactors leads to higher ethanol removal efficiency, less partial oxidation, lower amount of by-products and the complete mineralization of acetaldehyde.

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Driving carbon reduction strategies adoption in built environment – the moderating role of organizational culture

May 7, 2013, 5:40 pm
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Publication date: Available online 6 May 2013
Source:Building and Environment
Author(s): Peter S.P. Wong , Jason Zapantis
In recent years, numbers of strategies were advocated to foster carbon reduction in built environment. However, few studies have acknowledged that strategies adoption is a matter of organizational culture (OC). In this study, a conceptual model that depicts the hypothesized relationship among carbon reduction drivers, strategies adoption and OC is developed. The model is then tested with data collected via a survey conducted in Australia. The results suggest that the significant relationship between the carbon tax and the adoption of carbon reduction strategies can be further enhanced by OC in terms of goal clarity, rewards, and innovation. Surprisingly, stringent regulations may not necessarily induce adoption of carbon reduction strategies in built environment even if OC exists.

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Factors affecting horticultural and cleaning workers’ preference on cooling vests

May 7, 2013, 5:40 pm
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Publication date: Available online 6 May 2013
Source:Building and Environment
Author(s): A.P.C. Chan , Y. Yang , D.P. Wong , E.W.M. Lam , Y. Li
Outdoor workers are at high risk of suffering from heat-related illness when they are exposed to a hot and humid environment under prolonged working time. Providing suitable cooling vests for these workers might help alleviate heat stress during summer time. However, whether workers are willing to wear cooling vests is still uncertain because of various personal preferences. To understand the determinants of worker preferences on two kinds of cooling vests, field studies were conducted in construction, horticulture and cleaning, and airport apron services industries, respectively. Workers were asked to rate 18 items of subjective attributes from a self-administrated questionnaire. Based on 17 items of subjective attributes, workers revealed four underlying factors; namely, thermal comfort, usability, tactile comfort, and fabric hand (feel), as the underlying factors affecting their preference. Multiple linear regression analysis was conducted between the four underlying factors derived from factor analysis and one dependent variable ‘dislike–like’ to find out the reasons why horticultural and cleaning workers preferred one type of cooling vest over the others. Results indicated that while male and female workers were influenced differently by different underlying factors, usability was the common and determining factor having the strongest correlation with their preference regardless of gender difference. Thermal comfort, tactile comfort, and fabric hand (feel) were also important factors affecting their preferences. However, the choices of male workers were influenced more by thermal comfort, whereas female workers paid more attention to tactile comfort and fabric hand (feel). Therefore, gender differences should be considered in designing and constructing suitable cooling vests.

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