Thermal Comfort Criteria Research Articles

The effects of diffuser type on thermal flow and contaminant transport in high-speed train (HST) cabins – a numerical study

ABSTRACTRecalling the previous global outbreaks of diseases including severe acute respiratory syndrome spread in public transportation cabins, the investigation of transport characteristics of containments through the high-speed trains (HSTs) cabin is critical due to the currently fast development of high-speed rail around the world. For quantitatively analysing the effects of diffuser on ventilation and spread of diseases in HST cabins, computational fluid dynamics (CFD) models containing four different diffuser types were developed in this study. The drift-flux model and Lagrangian model were applied. Simulation results indicated that the diffuser type significantly affects overall cabin airflow pattern. Even though all four types of diffusers applied in HST cabins could satisfy the thermal comfort criterion, containments dispersion processes varied. Besides, gaseous contaminants and particle contaminants transport also varied in the same ventilation conditions. Importantly, contaminants had locked-up zones around passengers due to the uprising passengers' thermal plume against the descending ventilation airflow.

Why Are Naturally Ventilated Office Spaces Not Popular in New Zealand?

In this paper, we investigated the reason(s) why natural ventilation is not as popular as air-conditioned or mixed-mode ventilation systems in Green-rated office buildings in New Zealand. To achieve this, we had three objectives. Firstly, we reviewed the Green Star criteria for thermal comfort in office buildings to ascertain which ventilation system the NZ Green Star rating tool promotes. Secondly, we ascertained the perception of occupants in office buildings regarding thermal comfort. This was followed by an interview with building experts regarding factors that affect the use of natural ventilation in New Zealand offices. The findings showed that the NZ Green Star thermal comfort criteria encourage the use of mechanical ventilation over natural ventilation which results in designers opting for air conditioning systems in office designs. We observed that occupants of naturally ventilated spaces were least satisfied with the thermal comfort of their offices when compared with occupants of mixed-mode and air-conditioned offices. This study fulfils the need to encourage the use of natural ventilation in office environments by designers and building owners. Further study on other aspects of the indoor environment quality that is related to naturally ventilated systems such as lighting and noise is required in a bid to ascertain its viability in office environments.

Adaptive thermal comfort in the main Mexican climate conditions with and without passive cooling

The present work shows an adaptive thermal comfort modelling suitable for the main four climatic regions of Mexico, for cooling and heating seasons and for both air-conditioned and free-running buildings using passive cooling. The document has the aim of setting up an own thermal comfort criteria within the Mexican territory and thereby determining the upper limit of the indoor air temperature, for passive cooling, and the lower threshold, for active cooling. All this with the purpose of reaching the maximum of comfort with passive methods as well as minimizing the energy consumption when active cooling is on. The comfort model takes account of the main human and physical factors presented in previous surveyed studies. With this, it is found that for air-conditioned buildings the temperature set-point of the thermostat could be considerably raised and still maintaining indoor comfort. On the other hand, for free-running buildings, the sensation of discomfort could be decreased if the occupants are able to have the control of their environment by using controlling passive techniques namely natural ventilation and solar control systems.

Exploring Energy Conservation in Office Buildings with Thermal Comfort Criterion Towards Sustainable New Developments in Warm and Humid Climate

Abstract India is experiencing rapid urbanization and there is tremendous growth in the building construction sector since the last decade. India has proposed 100 smart cities and the offices/commercial built space is expected to increase fourfold between 2015 and 2030. Building sector consumes 40% of the world's energy and is the single leading contributor to anthropogenic climate change. The office buildings in the warm and humid region in India are mostly installed with air-conditioning to maintain indoor thermal comfort. This system consumes the most energy of all building services representing 55% of the total energy consumption in office buildings and has the largest potential in energy savings. As a case study, a six storey office building in Manipal in Coastal Karnataka, India is documented and simulated for indoor thermal comfort analysis. Various building envelope design strategies are examined in order to improve indoor temperatures and conserve energy towards sustainable new developments in warm and humid climate.

Impact of conservatory as a passive solar design of UK dwellings

The prime goal of professionals in the built environment is to build cost-effective, environmentally sustainable buildings. This work focuses on the viability of passive solar design strategies of conservatories in the UK in mitigating the impact of future climate change. It further shows that passive solar energy utilisation in building design can contribute to the reduction of dwelling energy consumption and enhancement of indoor thermal comfort. Synergetic passive design strategies that optimise solar energy gains through thermal simulation analyses of varying future climatic conditions, occupant behaviour, building orientation, thermal mass, advance glazing, appropriate ventilation and shading, which influence the potential thermal performance of the conservatory, are devised. The balanced energy benefits of reduction in energy consumption through the application of passive solar design principles for space heating in winter and the challenge of reducing excessive solar gains in summer are analysed using the Cibse TM52 adaptive thermal comfort criteria. The results show that judicious integration of passive solar design strategies in conservatories, with increasing conservatory size in elongated south-facing orientation with an aspect ratio of at least 1·67, could decrease energy consumption, enhance thermal comfort and help to mitigate the impact of climate change when the conservatory is neither heated nor air conditioned.

Thermal design of two-stage evaporative cooler based on thermal comfort criterion

Performance of two-stage evaporative coolers at various outdoor air conditions was numerically studied, and its geometric and physical characteristics were obtained based on thermal comfort criteria. For this purpose, a mathematical model was developed based on conservation equations of mass, momentum and energy to determine heat and mass transfer characteristics of the system. The results showed that two-stage indirect/direct cooler can provide the thermal comfort condition when outdoor air temperature and relative humidity are located in the range of 34–54 °C and 10–60 %, respectively. Moreover, as relative humidity of the ambient air rises, two-stage evaporative cooler with the smaller direct and larger indirect cooler will be needed. In building with high cooling demand, thermal comfort may be achieved at a greater air change per hour number, and thus an expensive two-stage evaporative cooler with a higher electricity consumption would be required. Finally, a design guideline was proposed to determine the size of required plate heat exchangers at various operating conditions.

The effectiveness of organic PCM based on lauric acid from coconut oil and inorganic PCM based on salt hydrate CaCl2.6H2o as latent heat energy storage system in Indonesia

A latent heat energy storage system utilizing phase change materials (PCM) is an alternative strategy to reduce the use of Air Conditioning (AC) system in big cities in Indonesia in order for energy conservation in the future. In this research we used two kinds of materials, namely organic PCM based on lauric acid from coconut oil (CO) and inorganic PCM based on salt hydrate CaCl2.6H2O, because they have thermophysical parameters suitable for human's thermal comfort application in the building. The CO which contained more than 50% lauric acid has the melting temperature (Tm) of about 26 °C and heat entalphy (ΔH) around 103 kJ/kg, while CaCl2.6H2O has the melting point of 29 °C and heat entalphy of 190 kJ/kg. In this paper we report the effectiveness of those two kinds of PCM in reducing the air temperature as one of some criteria for human's thermal comfort. The experiments were performed in a close and adiabatic room and the time-temperature measurements were done automatically using Arduino microcontroller and LM35 temperature sensor connected to the PC.

An Exhaustive Parametric Study on Major Passive Design Strategies of a Typical High-rise Residential Building in Hong Kong

This paper presents a comprehensive sensitivity analysis (SA) of the typical High-rise residential building in Hong Kong. A generic building model is constructed with proposed natural ventilation strategies subject to the examination of thermal comfort criteria. The numerical modelling exhaustively investigate the thermal and energy responses based on the variation of different passive design parameters. The parametric studies with respect to multiple output indices are able to prove that the window solar heat gain coefficient is the most influential architectural design factor. Different thermal comfort models including the Adaptive Comfort Standard (ACS) and Predicted Mean Vote (PMV) are compared in estimating the indoor environmental quality (IEQ) for the generic building. It is believed that sensitivity analysis benefit the identification of important inputs to facilitate further optimization of the building performance in initial plan stages.

Design and prototyping of a FRCC modular and climate responsive affordable housing system for underserved people in the pacific island nations

This paper outlines the process of design and prototyping of a modular housing system aimed at serving the needs of people in the Pacific island nations. Many people in these islands are economically challenged and live in sub-standard housing at low elevations, making them vulnerable to increased tropical storms brought about by climate change.A collaborative team comprised of architecture and engineering faculty and students is currently developing a system to address the need for improved housing in the Pacific islands based on the criteria of affordability, customizable design, thermal comfort, durability, sustainability, and local reproducibility.To best address the design criteria, the team reviewed indigenous building and tropical architecture literature, studied climactic factors, formed alternative design strategies, and selected the most promising for further development. A method of using precast fiber-reinforced cementitious composite (FRCC) modular components was chosen, with a limited number of parts to lower unit cost. The assembly was designed to allow homeowners to participate in the construction process, and the house is adaptable by adding or reconfiguring modules. To provide thermal comfort, the design evolved to include shading overhangs, a narrow floor plate, porous walls, and a ridge vent for stack ventilation. Durability is addressed through structural design and material selection. The structure is designed to withstand anticipated hurricane and storm surge events. Local reproducibility is sought by using materials and methods of construction possible with moderate workforce training and minimal capitalization costs.A successful housing system for the Pacific Islands must address cultural, environmental, constructional, and structural factors, and therefore benefits from a collaborative design approach involving both architects and engineers. The proposed system as developed to date appears to be a promising solution to provide affordable, sustainable, and resilient housing for underserved people in the Pacific islands. Pending availability of funding, a first prototype house is slated for construction on a Pacific island site and evaluated for cost, thermal comfort, climate effect resistance, and occupant satisfaction.

Human thermoneutral zone and thermal comfort zone: effects of mild heat acclimation

Overheating of buildings is currently a hot topic in the Western World. A significant amount of energy is needed for air conditioning and ventilation of public and commercial buildings. Nevertheless, up to 80% of the occupants are dissatisfied with the thermal environment, even though buildings meet thermal comfort criteria as determined by the ASHRAE Standard 55 and ISO Standard 7730. Physiological parameters such as sex, age, body composition and metabolic rate can have a great effect on an individual's perception of the thermal environment. A study among young Europeans indicated that the preferred ambient temperature might vary as much as 10 °C between individuals. However, it is not yet clear how an individual's thermal comfort zone (TCZ) relates to the physiological thermo-neutral zone (TNZ). Moreover, unlike thermoregulatory adaptations to strong repetitive heat challenges, it is unknown to what extent humans adapt to more mild warm ambient conditions in terms of subjective perception and thermo-regulatory physiology. Therefore, the present study aimed to investigate the relationship of an individual's TNZ and TCZ as well as the influence of 7 days of mild heat acclimation on TNZ and TCZ. Since the study is still ongoing, preliminary data will be presented.

An experimental investigation into the pull-down performances with different air distributions

The purpose of this study is to investigate the loads and lengths of the pull-down periods (the time used to achieve a comfortable thermal environment before a room is ready for occupation) with mixing ventilation, displacement ventilation and stratum ventilation. In a typical classroom in Hong Kong, experiments begin with the same initial hot thermal environment. Based on ASHRAE 55-2010, ISO Standard 7730 and literature, existing indices PMV, PD and ADPI, calculated from measured data, are used as the thermal comfort criteria to determine the end of the pull-down period. The results indicate that stratum ventilation outperforms the other two air distributions during the pull-down period in terms of rapidity and energy consumption. For the rapidity of the pull-down process, mixing ventilation spends a shorter time than displacement ventilation, while stratum ventilation spends less than half of the time the other two spend. The average pull-down load of stratum ventilation is only around a quarter of that of mixing ventilation or displacement ventilation, The exergy consumption of the chilled water used for the pull-down of stratum ventilation is also lower than that of the other two distributions.

Window operation and impacts on building energy consumption

Operable windows provide occupants with the ability to control local environments and satisfy human expectation to access outdoor environments. Operation behaviors or strategies for operable windows have substantial impacts on the indoor environment and building energy consumption. Facility managers complain about operable windows left open in buildings with conventional HVAC systems. However, optimum control strategies of window operation reduce energy consumption for buildings via natural ventilation or mixed-mode ventilation. This study focuses on the investigation of the impacts of window operation on building performance for different types of ventilation systems including natural ventilation, mixed-mode ventilation, and conventional VAV systems in a medium-size reference office building. A building performance simulation tool—EnergyPlus—is used to simulate window operation for each system type. Various control strategies of window operation, simulated using the energy management system feature (EMS) in EnergyPlus, are evaluated based on the criteria of thermal comfort and energy consumption. The investigation included the interaction between conventional VAV systems and window operation as well as control strategies for natural ventilation and mixed-mode ventilation. The results highlighted the impacts of window operation on energy use and comfort and identified HVAC energy savings of 17–47% with mixed-mode ventilation during summer for various climates.

Thermal Performance of Apartment (High-Rise) in Surabaya with Precast Concrete for the Building Envelope

Lack of horizontal land causes the development of vertical buildings. Residences in major cities are dominated by apartments from the low rise to the high rise types. Based on the information cited from Vivanews May 2, 2010, the number of apartments in Surabaya approximately 12 new apartment projects and has been built with a total of 5,000 units with an average of nearly 80% is sold in every apartment. Current sheath material that is widely used for apartment’s envelope is precast concrete. Precast concrete is the material that had been made at the factory in accordance with the form of the mold, then the molded concrete will be transported and installed to the building construction site. Precast concrete is chosen because it has several advantages when compared to conventional concrete structural system, including the efficiency of processing time, energy efficiency, and environmentally friendly. Given these statements, the researcher needs to know the thermal performance of apartment buildings (high-rise) in Surabaya with precast concrete building envelope. Expected to know the configuration of precast concrete materials in the building envelope, the researcher can construct an apartment building design proposals that meet the criteria of thermal comfort in tropical regions. This study aims to identify and explain the thermal performance of the precast concrete configuration in apartment buildings (high-rise) in Surabaya for the buiding envelope. The method that is used for this research is an experimental method to study the object with modeling strategies by Archipak for the simulation. The results shows that thermal performance of precast concrete pretty well applied to the apartment with thermal properties that support the value of the thermal performance of precast.

The role of a building's thermal properties on pupils' thermal comfort in junior school classrooms as determined in field studies

Recent thermal comfort research in a light-weight junior school building showed that children were more sensitive to higher temperatures than adults and subsequently that current thermal comfort standards were not appropriate for the assessment of their thermal environment. This paper presents a comparison of these survey results to those from a survey conducted in a medium-weight school building, in order to evaluate the role of the construction type on the results. Both surveys followed the same methodology, including thermal comfort questionnaires and measurements of indoor environmental variables. A total of 2990 responses were gathered. The buildings had an average difference in air temperature of 2.7 °C during occupied hours in the period of investigation (June and July 2012), with the medium-weight building being cooler than the light-weight building. However, the different construction type and the cooler overall thermal environment in the medium-weight school building had little impact on the pupils' overall thermal sensitivity. The comparison showed a general agreement on the pupils' warm thermal sensation trends, interpersonal variation and undeveloped adaptive behaviour. The results further support the finding that current thermal comfort criteria lead to an underestimation of pupils' thermal sensation during summer.

Heat Exchanger Design of Direct Evaporative Cooler Based on Outdoor and Indoor Environmental Conditions

Performance of a direct evaporative cooler (DEC) was numerically studied at various outdoor and indoor air conditions, with geometric and physical characteristics of it being extracted based on thermal comfort criteria. For this purpose, a mathematical model was utilized based on the equations of mass, momentum, and energy conservation to determine heat and mass transfer characteristics of the system. It is found that the DEC can provide thermal comfort conditions when the outdoor air temperature and relative humidity (RH) are in the range of 27–41 °C and 10–60%, respectively. The findings also revealed that by raising the RH of ambient air, the system will reach the maximum allowed RH faster and hence a smaller heat exchanger can be used when the ambient air has higher RH. Finally, performance of the DEC in a central province of Iran was investigated, and a design guideline was proposed to determine size of the required plate heat exchangers at various operating conditions.

Bayesian thermal comfort model

Thermal comfort assessment is a prime measure in indoor environment design to evaluate occupant satisfaction. Fanger's thermal comfort model using heat balance theory conducted by chamber test has been widely adopted for thermal environment design criteria. However, rising numbers of thermal comfort field studies show that Fanger's model is not a good predictor of actual thermal sensation and many field measurements were statistically insignificant. This study proposes a Bayesian approach to update our current beliefs about thermal comfort and shows that the maximum likelihood of posterior estimates is close to the actual percentage dissatisfied (APD) obtained from large sample field surveys. For small sample sizes, the Bayesian estimation is close to Fanger's prediction and gives a solution for the discrepancy of Fanger's model. Congruence between Fanger's model prediction and contemporary field survey data is quantified. This quantitative assessment on the belief in newly yielded thermal comfort data can be a solution to the choice of thermal comfort criteria in future thermal environment designs.

통기성 향상을 위한 하계비행복 설계 및 착용쾌적성 평가

This study verified the effect of summer flight ventilation developed in a previous study based on wearing comfort evaluation. Seven healthy males in their twenties volunteered for this experiment conducted in aclimatic chamber. The experiment consisted of three consecutive periods of rest (20 minutes), running on a treadmill (10 minutes) and recovery (20 minutes). A comparative evaluation was conducted on the general flight suit which had no ventilation holes and summer flight suit that use subjective satisfaction measures and objective measures. The subjective satisfaction was evaluated according to the criteria of temperature sensation, wet sensation, thermal comfort and fatigue sensation. The objective satisfaction was measured by skin temperature, microclimate (temperature and humidity), sweat rate and thermography. The comparative wearing evaluation identified the summer flight suit decreased the temperature between skin and suit by <TEX>$0.42^{\circ}C$</TEX> (upper arm), <TEX>$0.9^{\circ}C$</TEX> (calf) and the skin temperature by <TEX>$0.3^{\circ}C$</TEX> (shoulder), <TEX>$0.4^{\circ}C$</TEX> (upper arm), <TEX>$0.5^{\circ}C$</TEX> (calf) as compared to the general flight suit. The humidity inside the summer flight suit decreased at head (7.73%), shoulder (5.86%), upper arm (5.26%), and calf (8.73%) compared to the one inside the general flight suit. Thermography showed that the air flowed through ventilation holes (neck and armpit). The design of ventilation holes applied to the summer flight suit can be applicable to overall clothing that requires thermal comfort such as dust-free garments, mechanical clothing and combat uniforms.

Design guideline for application of earth-to-air heat exchanger coupled with solar chimney as a natural heating system

Abstract In the present paper, design of solar chimney (SC) and earth-to-air heat exchanger (EAHE) to meet thethermal need of flat buildings are studied regarding adaptive thermal comfort criteria. Investigation onthe effects of geometric features shows that the design of SC with the air gap and outlet sizes of 0.2 m andalso EAHE with the diameter and length of 0.5 and 25.0 m reveals better performance. Thermal comfortanalysis shows that the SC is capable to power the underground heating system during few hours of thesunny days even at the ambient temperature as low as 08C and the heating demand of 1000 W withoutneeding the auxiliary devices. In addition, the required numbers of SCs and the underground air channelsare strongly influenced by environmental outdoor conditions and heating demand of building and areapproximately calculated by: room volume/50and 2 ð room volume/50Þþ1, respectively. Keywords: Design; earth-to-air heat exchanger; natural heating; solar chimney Received 31 July 2013; revised 23 November 2013; accepted 4 January 2014

Assessing energy and thermal comfort of different low-energy cooling concepts for non-residential buildings

Energy consumption for cooling is growing dramatically. In the last years, electricity peak consumption grew significantly, switching from winter to summer in many EU countries. This is endangering the stability of electricity grids. This article outlines a comprehensive analysis of an office building performances in terms of energy consumption and thermal comfort (in accordance with static – ISO 7730:2005 – and adaptive thermal comfort criteria – EN 15251:2007 –) related to different cooling concepts in six different European climate zones. The work is based on a series of dynamic simulations carried out in the Trnsys 17 environment for a typical office building. The simulation study was accomplished for five cooling technologies: natural ventilation (NV), mechanical night ventilation (MV), fan-coils (FC), suspended ceiling panels (SCP), and concrete core conditioning (CCC) applied in Stockholm, Hamburg, Stuttgart, Milan, Rome, and Palermo. Under this premise, the authors propose a methodology for the evaluation of the cooling concepts taking into account both, thermal comfort and energy consumption.

Performance of hospital spaces in summer: A case study of a ‘Nucleus’-type hospital in the UK Midlands

Nucleus-type Hospital in Glenfield comprises connected cruciform blocks with numerous small courtyards between. The hospital has mechanical ventilation and perimeter heating. The wards have a hybrid ventilation strategy with a low rate of mechanical ventilation. Ventilation through windows is the main source of summer time cooling. This paper investigates the summer time performance of spaces that are mechanically ventilated but passively cooled. The paper presents the measured indoor temperatures in selected hospital spaces and compares them with thermal comfort criteria. Finally, future summer conditions for the ward space are predicted using a calibrated multi zone dynamic thermal model.During June to September 2010, the maximum indoor temperatures in the case study spaces varied between 27.3°C and 29.3°C. The nurse station was found to be the hottest area. During this period the performance of most of the monitored spaces was reasonably within the thermal comfort threshold as defined by HTM03-01. The simulation results demonstrate that light-touch low carbon interventions could produce comfortable conditions in bedrooms into the 2050s in UK Midlands.