[show abstract][hide abstract] ABSTRACT: Abstract
The current Indian indoor comfort standards do not reflect the country’s great cultural and climatic diversity. There have been very few reports on the actual environments in Indian offices in the last three decades. We conducted a thermal comfort field study in 28 naturally ventilated (NV) and air-conditioned (AC) offices in Chennai and Hyderabad for fourteen months, and collected 6048 responses from 2787 individuals. Warm humid and composite climates are experienced in these cities, and these two climates cover about 80% area of the country.
This paper proposes an adaptive thermal comfort model for South India based on this data. Mean comfort temperature was found to be 28.0 °C in NV mode, and 26.4 °C in AC mode on all data. Chennai had slightly higher comfort temperature. We found an adaptive relationship between the prevailing outdoor temperature and the comfortable indoor temperatures. Most of the environments in NV mode and about half in AC mode were warmer than the current Indian Standard upper limit (26 °C).
In most cases, the air speed was below 0.20 m/s. Most of the subjects used fans. Air speeds of 1 m/s increased the comfort temperature by 2.7 K in both the modes. Logistic regression predicted 87% and 50% fan usage at 29 °C in NV and AC modes respectively. Several factors prevented further thermal adaptation. We can potentially improve comfort and reduce air-conditioning by providing higher air speeds with energy-efficient fans. Such strategies may be vital given the scale of the scarcity of power.
Building and Environment 01/2014; · 2.43 Impact Factor
[show abstract][hide abstract] ABSTRACT: Large-eddy simulations (LESs) were performed on the reactive air pollutant dispersion in three types of urban street canyons that had various roof-height levels. Line sources that emit nitrogen monoxide (NO) were set on the bottom of the canyon space in each case. NO dispersed on the cavity eddy and reacted with ozone included in the free stream. The reactivity of air pollutants and the roof heights had a considerable influence on the concentrations of the pollutants inside street canyons. Deeper canyon spaces weakened the ventilation efficiency for pollutants generated inside the canyon. In contrast, variations in the roof height improved the ventilation efficiency. However, in terms of pollutants that came from outside the canyon, the concentration was the lowest for the case with the highest aspect ratio because of the effluent reactions that occurred during retention inside the canyon space. The correlation of the reactors’ concentrations was also inspected to reveal the influence of the turbulent nature of the atmosphere on the reaction rate. The correlation had a magnitude of more than 5% to 10% of the total reaction rate inside the street canyons, and it could reach 40% at the maximum in the case with an aspect ratio of 2.0.
Journal of Wind Engineering and Industrial Aerodynamics 07/2012; s 104–106:516–522. · 1.34 Impact Factor
[show abstract][hide abstract] ABSTRACT: In general, water pumped from a well used in a groundwater heat pump (GWHP) system is discharged to the well or the other wells. However, long-term pumping and injection may cause clogging of the wells, which is a major problem encountered when injecting groundwater into a well. “Reverse circulation” has been proposed as a solution to this problem, but this only results in temporary improvement of the injection efficiency and is not a permanent solution. With the aim of reducing the environment load and conserving groundwater resources, a groundwater circulation heat pump system was developed that is well suited for long-term use. This article provides an overview of the system and the results of real-scale experiments carried out at two sites (Chiba and Nagoya, Japan). These experiments have been conducted to evaluate the heating and cooling performance of the system. The system used at the Chiba site is equipped with two submersible pumps and two wells because of the deep groundwater level (–11 m (36 ft) G.L.). However, in the system at the Nagoya site, where the groundwater level is –4 m (13 ft) G.L., a land pump and a single well (for both production and injection) are used. Results show that the coefficient of performance (COP) of the groundwater heat pump is higher than that of the air-source heat pump. Furthermore, an automatic reverse circulation system was introduced that prevents clogging of the return well. Also, the effectiveness of a packer is confirmed for preventing short circuiting of the temperature in the aquifer in the case of the single well system. Finally, it is concluded that a small pumping rate and large temperature difference are very effective for reducing pumping-energy consumption and improving the coefficient of performance.
HVAC&R RESEARCH 08/2011; 17(4):556-565. · 0.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: Urban land surface schemes have been developed to model the distinct features of the urban surface and the associated energy exchange processes. These models have been developed for a range of purposes and make different assumptions related to the inclusion and representation of the relevant processes. Here, the first results of Phase 2 from an international comparison project to evaluate 32 urban land surface schemes are presented. This is the first large-scale systematic evaluation of these models. In four stages, participants were given increasingly detailed information about an urban site for which urban fluxes were directly observed. At each stage, each group returned their models' calculated surface energy balance fluxes. Wide variations are evident in the performance of the models for individual fluxes. No individual model performs best for all fluxes. Providing additional information about the surface generally results in better performance. However, there is clear evidence that poor choice of parameter values can cause a large drop in performance for models that otherwise perform well. As many models do not perform well across all fluxes, there is need for caution in their application, and users should be aware of the implications for applications and decision making. Copyright. 2010 Royal Meteorological Society
International Journal of Climatology 01/2011; 31:244-272. · 2.89 Impact Factor
[show abstract][hide abstract] ABSTRACT: We investigated the influence of meteorological factors that affect ozone in summer using both measurement analysis and numerical simulation. The results show that there is a close relationship between changes in meteorological conditions and variations in ozone concentrations over the central Kanto area. In summer, up to 84% of long-term variations in peak ozone concentrations may be accounted for by changes in the seasonally averaged daily maximum temperatures and seasonally averaged wind speeds. The ozone episodes in the Kanto region are dominated by three major patterns, of which Patterns I and II are regular summertime pressure patterns with a 26% and 16% frequency of occurrence, respectively. A detailed process analysis of ozone formation under urban heat island (UHI) at two areas in the Kanto region – urban and rural area – indicates that ozone formation is mainly controlled by chemistry, dry deposition, vertical transport, and horizontal transport processes. The groundlevel ozone concentrations are enhanced mainly by the vertical mixing of ozone-rich air from aloft, whereas dry deposition process mainly depletes ozone. Horizontal transport and chemistry processes play opposite roles in the net change of ozone concentration between the two areas. The results of numerical simulations also indicate that the sea breeze has significant effects on the ozone accumulation and distribution in the Kanto area. The high ozone was first observed in urban area and then was transported to the rural area by sea breeze. At rural area, the highest ozone concentrations were found in late afternoon, about two hours later in comparison with the urban area.
[show abstract][hide abstract] ABSTRACT: We assessed the ability of the MM5/CMAQ model to predict ozone (O3) air quality over the Kanto area and to investigate the factors that affect simulation of O3. We find that the coupled MM5/CMAQ model is a useful tool for the analysis of urban environmental problems. The simulation results were compared with observational data and were found to accurately replicate most of the important observed characteristics. The initial and boundary conditions were found to have a significant effect on simulated O3 concentrations. The results show that on hot and dry days with high O3 concentration, the CMAQ model provides a poor simulation of O3 maxima when using initial and boundary conditions derived from the CMAQ default data. The simulation of peak O3 concentrations is improved with the JCAP initial and boundary conditions. On mild days, the default CMAQ initial and boundary conditions provide a more realistic simulation. Meteorological conditions also have a strong impact on the simulated distribution and accumulation of O3 concentrations in this area. Low O3 concentrations are simulated during mild weather conditions, and high concentrations are predicted during hot and dry weather. By investigating the effects of different meteorological conditions on each model process, we find that advection and diffusion differ the most between the two meteorological regimes. Thus, differences in the winds that govern the transport of O3 and its precursors are likely the most important meteorological drivers of ozone concentration over the central Kanto area.
Journal of Environmental Sciences 01/2011; 23(2):236-46. · 1.77 Impact Factor
[show abstract][hide abstract] ABSTRACT: The summer climate around the Tokyo metropolitan area has been analysed on an urban scale, and the regional characteristics
of the thermal energy balance of a bayside business district in the centre of Tokyo (Otemachi) have been compared with an
inland residential district (Nerima), using a mesoscale meteorological model incorporating an urban canopy model. From the
results of the analysis, the mechanism of diurnal change in air temperature and absolute humidity in these areas is quantitatively
demonstrated, with a focus on the thermal energy balance. Moreover, effective countermeasures against urban heat-islands are
considered from the viewpoint of each region’s thermal energy balance characteristics. In addition to thermal energy outflux
by turbulent diffusion, advection by sea-breezes from Tokyo Bay discharges sensible heat in Otemachi. This mitigates temperature
increases during the day. On the other hand, because all sea-breezes must first cross the centre of Tokyo, it has less of
a cooling effect in Nerima. As a result, the air temperature during the day in Nerima is higher than that in Otemachi.
KeywordsHeat-island phenomenon-Meteorological mesoscale model-Thermal energy balance analysis-Urban canopy model
[show abstract][hide abstract] ABSTRACT: It is necessary for optimum design of GSHP systems to estimate accurately thermal properties of the designed ground and predict the heat extraction rate from the ground. Generally, experimental analysis has been used for the feasibility of system introduction such as thermal response test, pumping test or cone penetrating test, but it causes to increase estimation cost before the introduction, equivalent to tens of thousands of dollars in Japan. On the other hand, the heat exchange rate and the effect of the system on underground environment can be predicted by using numerical simulation. In this research, in order to estimate the effect of the ground thermal properties on system performance, numerical simulation has been conducted through the sensitivity analysis with the developed simulation tool. Furthermore, the method to develop an energy potential for GSHP system has been suggested and its application for Tokyo 23 ward area has been conducted with GIS data.
[show abstract][hide abstract] ABSTRACT: Recently, due to global warming and the heat-island effect, more and more people are exposed to the dangers of heat disorders. A hot thermal environment can be evaluated using various indices, such as new Standard Effective Temperature (SET∗) using the 2-Node Model (2 NM), Wet Bulb Globe Temperature (WBGT), Predicted Heat Strain (PHS) model, and so on. The authors aim to develop a safety evaluation approach for hot environments. Subject experiments are performed in a laboratory to comprehend the physiological response of the human body. The results are compared with the computed values from the 2 NM and PHS models, and improved the sweating model in 2 NM in order to take into account the relationship with metabolic rate. A demonstration is provided of using the new sweating model for evaluating thermal safety in a hot environment.
[show abstract][hide abstract] ABSTRACT: The present study explains the application of a numerical simulation to investigate the thermal environment of a new riverside
residential development in summer. The case study area consists of more than one hundred two-story detached houses built next
to a river near Tokyo, Japan. According to the meteorological data, prevailing wind directions are at an angle to the northbound
river flow affecting the microclimate of the study area in terms of surface temperature of land and buildings, air temperature
and wind distribution at pedestrian height. These factors have been estimated using the stepwise CFD (computational fluid
dynamics) simulation of radiation, conduction and convection. This method leads to an improvement of outdoor thermal environment
by manipulating the site design and layout planning scenarios. The effect of river, permeable pavements and green space on
thermal environment is examined by the site design options. Likewise, the impact of building arrangement is evaluated using
alternative layout planning scenarios. In total, five scenarios have been simulated for the proposed sustainable development
as explained in the paper. Above simulations provided an insight into the mitigation effects of each countermeasure. It is
also shown that the management of inflow paths and the creation of wind paths for the interior of the site have the potentials
to improve the outdoor thermal environment of riverside residential development.
Keywordsprevailing wind-thermal environment-layout planning-site design-riverside development-CFD
Building Simulation 01/2010; 3(1):51-61. · 0.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Technology directed at geothermal energy, one of our renewable energy sources, to heat and air-condition buildings has become very attractive in recent years following the significant developments in ground-source heat pump (GSHP) systems. In general, although the energy efficiency of GSHP systems is far superior to conventional air-source heat pump (ASHP) systems, GSHP system is still expensive. Therefore, GSHP system employs the foundation pile of buildings as heat exchanger is introduced in order to reduce the initial cost. When designing a GSHP system (especially in case of the energy pile system), it is necessary to accurately predict the heat extraction and injection rates of the heat exchanger. The thermal and hydraulic properties of the ground are very important to accurately predict heat transfer between the ground heat exchanger and the ground. In particular, those are the most important design parameters because energy pile system is installed only a few tens of meters deep. In this paper, an estimation method is suggested in order to determine the thermal and hydraulic properties of the ground for design the heat exchanger of energy pile system base on geotechnical investigation for the design the building's foundations. The use of results from generally applied geotechnical site investigation methods to estimate ground thermal and hydraulic properties was evaluated.
[show abstract][hide abstract] ABSTRACT: The groundwater heat pump (GWHP) system is an open-loop system that draws water from a well or surface water, passes it through a heat exchanger and discharges the water into an injection well or nearby river. By utilizing the relatively stable temperature of groundwater, GWHP system can achieve a higher coefficient of performance and can save more energy than conventional air-source heat pump (ASHP) system. The performance of the system depends on the condition of groundwater, especially temperature and depth, which affect performance of the heat pump and system. For the optimization of design and operation of GWHP systems, it is necessary to develop a simulation tool which can predict groundwater and heat flow and evaluate system performance comprehensively. In this research, 3D numerical heat-water transfer simulation and experiments utilizing real-scale equipment has been conducted in order to develop the optimization method for GWHP systems. Simulation results were compared with the experimental results, and the validity of the simulation model was confirmed. Furthermore, several case studies for the optimal operation method have been conducted by calculating the coefficient of performance on various groundwater and well conditions.
Energy and Buildings 01/2010; 42(1):69–75. · 2.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: We have assessed the contributions of individual physical and chemical atmospheric processes on ozone formation under different weather conditions during a typical summer month (August 2005) using the MM5/CMAQ modelling system. We found that the ozone episodes in the Kanto region are dominated by three major patterns, of which Patterns I and II are regular summertime pressure patterns with a 26% and 16% frequency of occurrence, respectively. A process analysis at two typical sites in the Kanto region – one located in the central region of Tokyo and the other located in the rural areas of Kanto – indicates that ozone formation is mainly controlled by advection, vertical diffusion, dry deposition, and chemical processes. The ground-level ozone concentrations are enhanced mainly by the vertical mixing of ozone-rich air from aloft, whereas the dry deposition and chemical processes mainly deplete ozone. By investigating the effects of each process under different weather conditions, we found that the significant decrease in ozone removal due to the chemical and advection processes under conditions of high stagnation is the most important cause of the enhanced levels of ozone in the central region of Tokyo. The results of this study can contribute to a better understanding of ozone formation in the Kanto region, and they may be valuable for local policy makers for further development planning.
[show abstract][hide abstract] ABSTRACT: Distributed energy systems based on cogeneration offer significant potential to save energy since they effectively utilize waste heat from power generators. However, unless there is an appropriate combination of machinery and operations, the planned performance cannot be achieved. Thus, it is quite difficult to determine the optimal combination of machinery and operations. For this, an optimal design approach is needed. In this study, a new optimal design method for building energy systems is proposed. There are an enormous variety of combinations with regard to energy supply and demand. This method designs the most efficient energy system by optimizing the operation of available systems with consideration for the optimal capacity of machinery in the systems. Optimization algorithms known as “genetic algorithms” (GAs) with the capacity to deal with non-linear optimization problems have been adopted in this optimization analysis. In this study, a single-building energy system is evaluated. The result shows that the proposed method is sufficiently capable of optimizing the design, and has the potential to be applied to very complex energy systems with appropriate improvements.
Energy and Buildings - ENERG BLDG. 01/2010; 42(7):985-991.
[show abstract][hide abstract] ABSTRACT: To achieve high heat pump efficiency, groundwater heat pump (GWHP) system uses groundwater, which is relatively stable AT temperature compared with outdoor air, as a heat source. However, it is difficult to meet annual heating and cooling loads using only groundwater as a heat source. In order to optimize the operation method of GWHP systems, it is necessary to develop a system utilizing both groundwater and air sources according to the building load conditions. Furthermore, during intermediate seasons (such as spring and autumn) with reduced heating and cooling loads, GWHP system is less efficient than air source heat pump (ASHP) system according to temperature conditions. In order to more efficiently use GWHP systems, it is necessary to develop a system which utilizes both groundwater and air sources according to temperature conditions and building loads. This research has developed a GWHP system that employs a hybrid heat pump system with groundwater wells using dual groundwater and air heat sources. In this paper, the annual performance of the developed system has been calculated, and several case studies have been conducted on the effect of introduction location, refrigerant and pumping rate. Furthermore, the coefficient of system performance and the effects on underground environments have been evaluated by real-scale experiment using two wells.
Energy and Buildings - ENERG BLDG. 01/2010; 42(6):909-916.
[show abstract][hide abstract] ABSTRACT: Urbanization is progressing rapidly in many Asian cities. The process of urbanization has modified the land use from natural environment into built environment. It alters not only the surface energy balance of the urban canopy, but also brings about a great quantity of anthropogenic sources of waste heat through air-conditioning, cars, etc. In addition, the effect of urbanization on urban wind environment is likewise significant. Thus, the primary precondition is to understand how the urban environment affects the physical and climatic pattern in and around the city resulting from urban encroachments. Commonly, wind-tunnel measurements and observational campaigns enable us to understand the physical processes that take place with the morphology of urban areas. This understanding is then used to represent these processes within numerical models of different urban scales. The ever-increasing computational power together with highresolution computational fluid dynamic models has now become a useful tool to gain significant insight into detailed processes occurring within the urban context. This chapter gives an overview of the latest simulation studies for mesoscale and microscale climates, and also the assessment tools used in urban climate research. Various assessment tools are introduced and classified according to corresponding modelling scales. Next, the chapter addresses recent achievements in urban climate research for urban thermal environment studies. Examples of numerical results obtained by researchers of Japan are presented.
Advances in Building Energy Research 04/2009; 3(1):147-188.