Evaluating the thermal comfort performance of heating systems using a thermal manikin with human thermoregulatory control

© International Society of the Built Environment. © The Author(s) 2014. The evaluation of the local thermal comfort and application of thermal manikins can further assist the design and selection of heating systems. This study aimed at evaluating the thermal comfort performance of different heating systems using a newly developed thermal manikin with an enhanced thermal control. The heating systems for a workstation, included a conventional radiator (convector) mounted under the window, heated floor in the occupied zone and an infrared heater mounted to the ceiling. The experiments were conducted in a test room with a façade attached to a climate chamber to simulate outdoor winter conditions. In these experiments, the supplied power for the different systems was kept constant to independently quantify the differences in their thermal comfort performance at same energy consumption. The thermal manikin was deployed in the occupied zone to evaluate the local and overall thermal comfort under each system using the equivalent temperature (Teq) approach. The thermoregulatory control used in the manikin operation is based on a model of human thermoregulation that interacts accurately with the surrounding environment through real-time measurements. The results showed that at the same energy consumption of the different systems, the variations in local thermal comfort levels were up to 1 on the comfort scale

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

This is the post-print version of the Article. The official published version can be accessed from the link below. Copyright @ 2013 Elsevier.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.This work was funded by the UK Engineering and Physical Sciences Research Council (EPSRC), Grant No: EP/H004181/1

Dynamic thermal simulation of advanced natural ventilation in buildings : current and future usage, UK exemplar

This paper evaluates the use of advanced natural ventilation (ANV) strategies in a range of climatic conditions from four cities in the UK. A prototype ANV system was proposed to determine the most effective case in mitigating overheating. The case was then assessed under identical simulation conditions for all four ANV strategies. The overheating criteria used in the research include the single temperature criterion from CIBSE Guide A and the adaptive thermal comfort overheating criteria from BS EN 15251. Both the current and future ‘Design Summer Year (DSY)’ weather data were used to examine the thermal performances of the proposed design. The findings show that shading, night cooling and heavy weight structures (ceiling) were all useful in mitigating overheating, with night cooling being identified as the most effective measure. The work assessed the use of ANV in both current and future scenarios to quantify the limits of outdoor environmental conditions under which natural ventilation is an effective strategy for achieving thermal comfort. The adaptive thermal comfort overheating criteria were proved to be easier to meet compared with the CIBSE single temperature criterion. With the adaptive overheating criteria, the given design is predicted to not overheat until 2050 in London Heathrow; and for other places evaluated in the UK (Edinburgh, Manchester & Birmingham), the design passes these criteria. The Centre-in ANV strategies proved to be more effective than the Edge-in strategies for space cooling due to the extended structure thermal mass

An experimental study of air flow and temperature distribution in a room with displacement ventilation and a chilled ceiling

Displacement ventilation and chilled ceiling panel systems are potentially more energy efficient than conventional air conditioning systems and are characterized by the presence of vertical temperature gradients and significant radiant asymmetry. The characteristics of this type of system have been studied by making temperature and air flow measurements in a test chamber over a range of operating parameters typical of office applications. Results from the displacement ventilation study are consistent with other studies and show that normalized temperature profiles are independent of internal heat gain. Linear temperature gradients in the lower part of the room were found, in all cases, to be driven by convection from the adjacent walls. Significant mixing, indicated by reduced temperature gradients, was evident in the upper part of the room in the chilled ceiling results at higher levels of heat gain. Visualization experiments, velocity measurements and related numerical studies indicated that with greater heat gains the plumes have sufficient momentum to drive flow across the ceiling surface and down the walls. The significance of forced, as opposed to natural convection, is also suggested by relatively low Richardson Number (Ri) values found near the ceiling. Furthermore, in cases with moderately high internal gains, comparison of the temperature gradients indicated that the effect of ceiling surface temperature on the degree of mixing and the magnitude of the temperature gradient were of secondary importance. These findings are in contrast to the view that it is natural convection at the ceiling that causes enhanced mixing

Correlations in thermal comfort and natural wind

Many field surveyshaveshownthatnaturallyventilatedbuildingsarefavorabletohumanthermal comfort andmayallowhighercoolingtemperaturesthanair-conditionedbuildings.Recreatingnatural wind characteristicswithamechanicalcoolingsystemmaydiminishthedrawbacksofconventional cooling systemssuchasdraftsandhighenergydemands.Naturalwindcharacteristics(windvelocity, direction, turbulentintensity,temperatureandrelativehumidity)wererecordedinamountain environmentandcorrelatedwiththehumanthermalsensationof48subjects.Naturalwind fluctuation characteristicswereanalyzedusingtheFastFourierTransform(FFT)analysis.Thedynamiccharacter- istics ofnaturalwindwereaveragedthroughthepowerspectrumexponent (β−value),whichrepresents the energydistributionoftheturbulent flowofnaturalwind.Thepowerspectrumexponent (β−value)of the naturalwindwilldecreasewhenthemeanvelocityincreases,whileitwillincreasewhenthe turbulent intensityincreases.Thepowerspectrumexponent (β−value)wascorrelated(Spearman's rank coefficient¼0.56, po0.001)withthermalcomfort.Thepowerspectrumexponent(β-value)forpeople feeling comfortablehasamedianvalueof1.62[1.41–1.80forthe first andthirdquartiles,respectively] and the β−valueforpeoplefeelinguncomfortablehasamedianvalueof1.10[0.97–1.25]. & 2013ElsevierLtd.Allrightsreserved

Indoor comfort and adaptation in low-income and middle-income residential buildings in a Nigerian city during a dry season

This paper investigates occupants' comfort, adaptation and their responses during the dry season in low-income to middle-income residential buildings in Abuja, Nigeria. The study aims to provide empirical data on occupants' comfort through evaluating 171 households in four different locations in Abuja. The study considered a combination of different research methods for data collection. Post-occupancy surveys were used to evaluate the buildings and residents' adaptation within the thermal environment. Thermal comfort surveys were also carried out in eight low-income residential households to assess occupants' perception of the thermal environment. Based on the short duration of the physical measurements, building simulation was also used to examine thermal comfort of occupants for an extended period. The Post Occupancy Evaluation (POE) results revealed over 70% of the occupants were dissatisfied with their thermal environment. The comfort surveys reported similar results with over 65% of the responses revealed being ‘uncomfortably warm’. The results showed an overall mean temperature of all the measured case studies to be 31.7 °C and the average temperature (predicted) of 30.7 °C. The neutral temperatures were in a range of 28°C–30.4 °C compared to the preferred temperature range of 27.5°C–29.4 °C. The prevalence of thermal discomfort highlights the need to explore the possibilities of reducing internal temperatures, particularly by passive means (fabric, shading, insulation etc.) given the need to avoid or reduce the need for air conditioning to make the buildings energy-efficient for low to middle income groups

Effect of thermal comfort on occupant productivity in office buildings : response surface analysis

Thermal environment is one of the main factors that influence occupants' comfort and their productivity in office buildings. There is ample research that outlines this relationship between thermal comfort and occupant productivity. However, there is a lack of literature that presents mathematical relationship between them. This paper presents a research experimental study that investigates effects of indoor environmental quality factors on thermal comfort and occupant productivity. This study was conducted by collecting indoor environmental quality parameters using sensors and online survey for twelve months. Data analysis was done using Response Surface Analysis to outline any mathematical relationship between indoor environmental quality and occupant productivity. The outlined relationships confirmed dependencies of occupant thermal comfort and productivity on various indoor environmental factors. These dependencies include the effect of CO2 concentration, VOC concentration. These relationships were analysed to rank nine indoor environmental parameters as per the degree of effect on occupant thermal comfort and productivity. These findings would help design professionals to design better office design that would improve occupants’ comfort and their productivity. Study results have different implications for professionals working in design, construction and operation of office buildings. It is recommended that design guidelines for office buildings should consider occupant productivity and incorporate recommended range for indoor environmental quality parameters in respective categories and criteria

The effect of passive measures on thermal comfort and energy conservation. A case study of the Hot Summer and Cold Winter climate in the Yangtze River region

The energy consumption for heating and cooling of buildings in the cities located within the boundaries of the Hot Summer and Cold Winter (HSCW) zone in China is rapidly increasing due to the increased comfort expectations from well-resourced occupants. Guidance on how and to what extent it is possible to improve energy efficiency of buildings is thus required by policy makers as well as designers and building managers. The aim of this study is to demonstrate how the use of climate-sensitive passive design solutions can help the improvement of indoor thermal conditions while reducing the energy needs and ultimately carbon emissions. An extensive parametric analysis of several passive strategies such as building orientation, thermal insulation, glazing area, shading devices, air tightness and natural ventilation, is carried out for a typical apartment block located in the cities of Chongqing, Changsha and Shanghai, which lays respectively in the upper, middle and downstream of the Yangtze River. Detailed hourly dynamic simulations show how it is possible to extend the non-heating/cooling period and reduce the peak loads, highlighting the potentialities of each strategy according to different climate constraints. The recommended strategies provides quantitative guidance to either design of new or retrofitting of existing buildings. This research contributes to the building energy conservation knowledge for policy-makers, developers and building designers with insight on the feasibilities of the application of passive measures for the residential buildings located in the Yangtze River region with hot summer and cold winter climates

Restaurant outbreak of Legionnaires' disease associated with a decorative fountain: an environmental and case-control study

BACKGROUND: From June to November 2005, 18 cases of community-acquired Legionnaires' disease (LD) were reported in Rapid City South Dakota. We conducted epidemiologic and environmental investigations to identify the source of the outbreak. METHODS: We conducted a case-control study that included the first 13 cases and 52 controls randomly selected from emergency department records and matched on underlying illness. We collected information about activities of case-patients and controls during the 14 days before symptom onset. Environmental samples (n = 291) were cultured for Legionella. Clinical and environmental isolates were compared using monoclonal antibody subtyping and sequence based typing (SBT). RESULTS: Case-patients were significantly more likely than controls to have passed through several city areas that contained or were adjacent to areas with cooling towers positive for Legionella. Six of 11 case-patients (matched odds ratio (mOR) 32.7, 95% CI 4.7-infinity) reported eating in Restaurant A versus 0 controls. Legionella pneumophila serogroup 1 was isolated from four clinical specimens: 3 were Benidorm type strains and 1 was a Denver type strain. Legionella were identified from several environmental sites including 24 (56%) of 43 cooling towers tested, but only one site, a small decorative fountain in Restaurant A, contained Benidorm, the outbreak strain. Clinical and environmental Benidorm isolates had identical SBT patterns. CONCLUSION: This is the first time that small fountain without obvious aerosol-generating capability has been implicated as the source of a LD outbreak. Removal of the fountain halted transmission