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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Modelování prostředí v kabině osobního automobilu / Simulation of indoor environment in a car cabin

Tuka, Ján January 2011 (has links)
The thesis deals with the evaluation of indoor environment cab passenger car, with a focus on thermal comfort of passengers. The theoretical part contains the fundamentals of heat transfer, analysis of the aspects affecting human thermal comfort and its assessment methods. A brief description of the ventilation and air conditioning systems used in passenger cars is mentioned. The practical part includes numerical simulations of indoor environment, in selected driving modes and at different climatic conditions. Results of simulations lead to evaluation the status of the internal environment in terms of thermal comfort.
52

Thermal analysis of the internal climate condition of a house using a computational model

Knutsen, Christopher 31 January 2021 (has links)
The internal thermal climatic condition of a house is directly affected by how the building envelope (walls, windows and roof) is designed to suit the environment it is exposed to. The way in which the building envelope is constructed has a great affect on the energy required for heating and cooling to maintain human thermal comfort. Understanding how the internal climatic conditions react to the building envelope construction is therefore of great value. This study investigates how the thermal behaviour inside of a simple house reacts to changes made to the building envelope with the objective to predict how these changes will affect human thermal comfort when optimising the design of the house. A three-dimensional numerical model was created using computational fluid dynamic code (Ansys Fluent) to solve the governing equations that describe the thermal properties inside of a simple house. The geometries and thermophysical properties of the model were altered to simulate changes in the building envelope design to determine how these changes affect the internal thermal climate for both summer and winter environmental conditions. Changes that were made to the building envelope geometry and thermophysical properties include: thickness of the exterior walls, size of the window, and the walls and window glazing constant of emissivity. Results showed that there is a substantial difference in indoor temperatures, and heating and cooling patterns, between summer and winter environmental conditions. The thickness of the walls and size of the windows had a minimal effect on internal climate. It was found that the emissivity of the walls and window glazing had a significant effect on the internal climate conditions, where lowering the constant of emissivity allowed for more stable thermal conditions within the human comfort range.
53

Ambient Micro-Climate and Thermal Comfort Assessment of Davis Wade Stadium during the 2016 Football Season

Collins, Andrew 30 April 2021 (has links)
College football stadiums host anywhere from 15,000 to 115,000 people each Saturday from late summer to early winter and leave fans exposed to ambient conditions. Amplified heat from stadium infrastructure substantially impact attendants’ thermal comfort. In order to assess personal heat exposure and mitigate exposure misclassification, temperature and relative humidity sensors (iButtons) were placed throughout Mississippi State University’s Davis Wade Stadium during the 2016 Football Season. iButton measurements established a micro-climate and compared its readings to the Soil Climate Analysis Network site 1.2 miles north of the stadium. The program RayMan Pro modeled a Physiological Equivalent Temperature (PET) micro-climate to create an individualized heat metric. The results of this study assess stadium occupants’ thermal comfort through Heat Index and PET. Heat-related health outcomes were examined regarding thermal comfort and the stadium micro-climate using data from the stadium’s EMS calls and First Aid stations during game days.
54

Assessing the impact of the indoor environment on productivity : A case study in a university building in Stockholm

Hellström, Petter January 2018 (has links)
The impact that the indoor environment has on productivity is a topic that has been investigated in numerous studies. There are a variety of different methods that have been used to evaluate productivity with. There are quantitative methods and there are qualitative ones, and both have been used in the literature as indicators or real productivity. The quantitative ones are for instance short arithmetical or linguistic performance tests or measurements of the actual quantitative output of a job. Qualitative assessments of productivity consist of different ways of allowing the subjects to rate their own productivity. Both these two approaches of evaluating productivity are claimed to be subject to different issues, and the question of which way is preferable is a matter of contention among the researchers. The quantitative approach is claimed to be unable to reflect the complex and qualitative output of many modern jobs, while the qualitative one is believed to be highly influenced by bias. This master’s degree project has investigated the associations between the two approaches and conducted a qualitative assessment of the impact of the indoor environment on the productivity in a university building in Stockholm. Numerous studies have been reviewed that include both quantitative evaluations of productivity and qualitative evaluations of the indoor environment. Qualitative evaluations are for instance evaluations of environmental satisfaction, as well as evaluations of healthiness and productivity. The relationship between the quantitative measurements and the subjective evaluation is indeed complex. However, there appears to be a consistency to some extent between the two, and the trend seems to indicate that occupants who are more productive are also more satisfied with the indoor environment or perceive themselves to be healthier or more productive. A working hypothesis has been formulated; that subjective evaluations of the indoor environment may act as indicators of productivity. This approach has been used in a university building in Stockholm, where the productivity of the students has been evaluated through a survey, together with physical measurements of the indoor environment. The survey is designed based on the current literature within the field. It has a large emphasis on productivity, with several questions concerning it directly and indirectly. The physical parameters that were measured were radiant temperature, air velocity, relative humidity, CO2- concentration and sound pressure level. Considerable correlations were observed between perceived productivity and environmental satisfaction, perceived environmental control and between different ways of evaluating productivity subjectively. The correlations between the physical measurements and the subjective evaluations were in general considerably weaker than the ones between the different subjective parameters. The correlations between the mean CO2-concentration and productivity was weak, and similar findings were obtained concerning sound pressure level. This emphasise the importance of heeding the opinions of the occupants while evaluating the performance of a building, as physical measurements alone appear to be unable to reflect the users’ perspective reliably. The correlation between the thermal parameters (evaluated by the PMV- value) and the subjective evaluations were, on the other hand, considerably stronger. This may indicate that the thermal parameters are among the most influential ones in creating a productive workplace. Furthermore, the study discusses different methods that have been used to evaluate productivity with. It discusses their weaknesses and strengths and what elements they contain that may be used for future studies of productivity.
55

Decentralized HVAC Operations: Novel Sensing Technologies and Control for Human-Aware HVAC Operations

Jung, Wooyoung 13 April 2020 (has links)
Advances in Information and Communication Technology (ICT) paved the way for decentralized Heating, Ventilation, and Air-Conditioning (HVAC) HVAC operations. It has been envisioned that development of personal thermal comfort profiles leads to accurate predictions of each occupant's thermal comfort state and such information is employed in context-aware HVAC operations for energy efficiency. This dissertation has three key contributions in realizing this envisioned HVAC operation. First, it presents a systematic review of research trends and developments in context-aware HVAC operations. Second, it contributes to expanding the feasibility of the envisioned HVAC operation by introducing novel sensing technologies. Third, it contributes to shedding light on viability and potentials of comfort-aware operations (i.e., integrating personal thermal comfort models into HVAC control logic) through a comprehensive assessment of energy efficiency implications. In the first contribution, by developing a taxonomy, two major modalities – occupancy-driven and comfort-aware operations – in Human-In-The-Loop (HITL) HVAC operations were identified and reviewed quantitatively and qualitatively. The synthesis of previous studies has indicated that field evaluations of occupancy-driven operations showed lower potentials in energy saving, compared to the ones with comfort-aware operations. However, the results in comfort-aware operations could be biased given the small number of explorations. Moreover, required data representation schema have been presented to foster constructive performance assessments across different research efforts. In the end, the current state of research and future directions of HITL HVAC operations were discussed to shed light on future research need. As the second contribution, moving toward expanding the feasibility of comfort-aware operations, novel and smart sensing solutions have been introduced. It has been noted that, in order to have high accuracy in predicting individual's thermal comfort state (≥90%), user physiological response data play a key part. However, the limited number of applicable sensing technologies (e.g., infrared cameras) has impeded the potentials of implementation. After defining required characteristics in physiological sensing solutions in context of comfort-aware operations (applicability, sensitivity, ubiquity, and non-intrusiveness), the potentials of RGB cameras, Doppler radar sensors, and heat flux sensors were evaluated. RGB cameras, available in many smart computing devices, could be a ubiquitous solution in quantifying thermoregulation states. Leveraging the mechanism of skin blood perfusion, two thermoregulation state quantification methods have been developed. Then, applicability and sensitivity were checked with two experimental studies. In the first experimental study aiming to see applicability (distinguishing between 20 and 30C with fully acclimated human bodies), for 16 out of 18 human subjects, an increase in their blood perfusion was observed. In the second experimental study aiming to evaluate sensitivity (distinguishing responses to a continuous variation of air temperature from 20 to 30C), 10 out of 15 subjects showed a positive correlation between blood perfusion and thermal sensations. Also, the superiority of heat flux data, compared to skin temperature data, has been demonstrated in predicting personal thermal comfort states through the developments of machine-learning-based prediction models with feature engineering. Specifically, with random forest classifier, the median value of prediction accuracy was improved by 3.8%. Lastly, Doppler radar sensors were evaluated for their capability of quantifying user thermoregulation states leveraging the periodic movement of the chest/abdomen area induced by respiration. In an experimental study, the results showed that, with sufficient acclimation time, the DRS-based approach could show distinction between respiration states for two distinct air temperatures (20 and 30C). On the other hand, in a transient temperature without acclimation time, it was shown that, some of the human subjects (38.9%) used respiration as an active means of heat exchange for thermoregulation. Lastly, a comprehensive evaluation of comfort-aware operations' performance was carried out with a diverse set of contextual and operational factors. First, a novel comfort-aware operation strategy was introduced to leverage personal sensitivity to thermal comfort (i.e., different responses to temperature changes; e.g., sensitive to being cold) in optimization. By developing an agent-based simulation framework and thorough diverse scenarios with different numbers and combinations of occupants (i.e., human agents in the simulation), it was shown that this approach is superior in generating collectively satisfying environments against other approaches focusing on individual preferred temperatures in selection of optimized setpoints. The energy implications of comfort-aware operations were also evaluated to understand the impact from a wide range of factors (e.g., human and building factors) and their combinatorial effect given the uncertainty of multioccupancy scenarios. The results demonstrated that characteristics of occupants' thermal comfort profiles are dominant in impacting the energy use patterns, followed by the number of occupants, and the operational strategies. In addition, when it comes to energy efficiency, more occupants in a thermal zone/building result in reducing the efficacy of comfort-driven operation (i.e., the integration of personal thermal comfort profiles). Hence, this study provided a better understanding of true viability of comfort-driven HVAC operations and provided the probabilistic bounds of energy saving potentials. These series of studies have been presented as seven journal articles and they are included in this dissertation. / Doctor of Philosophy / With vision of a smart built environment, capable of understanding the contextual dynamics of built environment and adaptively adjusting its operation, this dissertation contributes to context-aware/decentralized HVAC operations. Three key contributions in realization of this goal include: (1) a systematic review of research trends and developments in the last decade, (2) enhancing the feasibility of quantifying personal thermal comfort by presenting novel sensing solutions, and (3) a comprehensive assessment of energy efficiency implications from comfort-aware HVAC operations with the use of personal comfort models. Starting from identifying two major modalities of context-aware HVAC operations, occupancy-driven and comfort-aware, the first part of this dissertation presents a quantitative and qualitative review and synthesis of the developments, trends, and remaining research questions in each modality. Field evaluation studies using occupancy-driven operations have shown median energy savings between 6% and 15% depending on the control approach. On the other hand, the comfort-aware HVAC operations have shown 20% energy savings, which were mainly derived from small-scale test beds in similar climate regions. From a qualitative technology development standpoint, the maturity of occupancy-driven technologies for field deployment could be interpreted to be higher than comfort-aware technologies while the latter has shown higher potentials. Moreover, by learning from the need for comparing different methods of operations, required data schemas have been proposed to foster better benchmarking and effective performance assessment across studies. The second part of this dissertation contributes to the cornerstone of comfort-aware operations by introducing novel physiological sensing solutions. Previous studies demonstrated that, in predicting individual's thermal comfort states, using physiological data in model development plays a key role in increasing accuracy (>90%). However, available sensing technologies in this context have been limited. Hence, after identifying essential characteristics for sensing solutions (applicability, sensitivity, ubiquity, and non-intrusiveness), the potentials of RGB cameras, heat flux sensors, and Doppler radar sensors were evaluated. RGB cameras, available in many smart devices, could be programmed to measure the level of blood flow to skin, regulated by the human thermoregulation mechanism. Accordingly, two thermoregulation states' quantification methods by using RGB video images have been developed and assessed under two experimental studies: (i) capturing subjects' facial videos in two opposite temperatures with sufficient acclimation time (20 and 30C), and (ii) capturing facial videos when subjects changed their thermal sensations in a continuous variation of air temperature from 20 to 30C. Promising results were observed in both situations. The first study had subjects and 16 of them showed an increasing trend in blood flow to skin. In the second study, posing more challenges due to insufficient acclimation time, 10 subjects had a positive correlation between the level of blood flow to skin with thermal sensation. With the assumption that heat flux sensing will be a better reflection of thermoregulation sates, a machine learning framework was developed and tested. The use of heat flux sensing showed an accuracy of 97% with an almost 4% improvement compared to skin temperature. Lastly, Doppler radar sensors were evaluated for their capability of quantifying thermoregulation states by detecting changes in breathing patterns. In an experimental study, the results showed that, with sufficient acclimation time, the DRS-based approach could show distinction between respiration states for two distinct air temperatures (20 and 30C). However, using a transient temperature was proven to be more challenging. It was noted that for some of the human subjects (38.9%), respiration was detected as an active means of heat exchange. It was concluded that specialized artifact removal algorithms might help improve the detection rate. The third component of the dissertation contributed by studying the performance of comfort-driven operations (i.e., using personal comfort preferences for HVAC operations) under a diverse set of contextual and operational factors. Diverse scenarios for interaction between occupants and building systems were evaluated by using different numbers and combinations of occupants, and it was demonstrated that an approach of addressing individual's thermal comfort sensitivity (personal thermal-comfort-related responses to temperature changes) outperforms other approaches solely focusing on individual preferred temperatures. The energy efficiency implications of comfort-driven operations were then evaluated by accounting for the impact of human and building factors (e.g., number of thermal zones) and their combinations. The results showed that characteristics of occupants' thermal comfort profiles are dominant in driving the energy use patterns, followed by the number of occupants, and operational strategies. As one of the main outcomes of this study, the energy saving and efficiency (energy use for comfort improvement) potentials and probabilistic bounds of comfort-driven operations were identified. It was shown that keeping the number of occupants low (under 6) in a thermal zone/building, boosts the energy saving potentials of comfort-driven operations. These series of studies have been presented as seven journal articles, included in this dissertation.
56

Directional Airflow for HVAC Systems

Abedi, Milad January 2019 (has links)
Directional airflow has been utilized to enable targeted air conditioning in cars and airplanes for many years, where the occupants could adjust the direction of flow. In the building sector however, HVAC systems are usually equipped with stationary diffusors that can only supply the air either in the form of diffusion or with fixed direction to the room in which they have been installed. In the present thesis, the possibility of adopting directional airflow in lieu of the conventional uniform diffusors has been investigated. The potential benefits of such a modification in control capabilities of the HVAC system in terms of improvements in the overall occupant thermal comfort and energy consumption of the HVAC system have been investigated via a simulation study and an experimental study. In the simulation study, an average of 59% per cycle reduction was achieved in the energy consumption. The reduction in the required duration of airflow (proportional to energy consumption) in the experimental study was 64% per cycle. The feasibility of autonomous control of the directional airflow, has been studied in a simulation experiment by utilizing the Reinforcement Learning algorithm which is an artificial intelligence approach that facilitates autonomous control in unknown environments. In order to demonstrate the feasibility of enabling the existing HVAC systems to control the direction of airflow, a device (called active diffusor) was designed and prototyped. The active diffusor successfully replaced the existing uniform diffusor and was able to effectively target the occupant positions by accurately directing the airflow jet to the desired positions. / M.S. / The notion of adjustable direction of airflow has been used in the car industry and airplanes for decades, enabling the users to manually adjust the direction of airflow to their satisfaction. However, in the building the introduction of the incoming airflow to the environment of the room is achieved either by non-adjustable uniform diffusors, aiming to condition the air in the environment in a homogeneous manner. In the present thesis, the possibility of adopting directional airflow in place of the conventional uniform diffusors has been investigated. The potential benefits of such a modification in control capabilities of the HVAC system in terms of improvements in the overall occupant thermal comfort and energy consumption of the HVAC system have been investigated via a simulation study and an experimental study. In the simulation study, an average of 59% per cycle reduction was achieved in the energy consumption. The reduction in the required duration of airflow (proportional to energy consumption) in the experimental study was 64% per cycle on average. The feasibility of autonomous control of the directional airflow, has been studied in a simulation experiment by utilizing the Reinforcement Learning algorithm which is an artificial intelligence approach that facilitates autonomous control in unknown environments. In order to demonstrate the feasibility of enabling the existing HVAC systems to control the direction of airflow, a device (called active diffusor) was designed and prototyped. The active diffusor successfully replaced the existing uniform diffusor and was able to effectively target the occupant positions by accurately directing the airflow jet to the desired positions.
57

Avaliação do conforto térmico dos apartamentos do BNH da cidade de Santos. / Thermal comfort evaluation of social dwellings in the city of Santos.

Garcia, Thiago dos Santos 05 May 2015 (has links)
Boas alternativas nas escolhas de materiais construtivos em um projeto arquitetônico possibilitam de forma mais assertiva os aspectos de conforto térmico em habitações de interesse social. A existência de normas que determinem alguns parâmetros de conforto térmico não significa que a unidade habitacional esteja dentro dos parâmetros ideais, já que dependem de bons projetos, correta execução da obra e estarem adequadas às restrições econômicas dos usuários. Esta pesquisa teve como motivação revelar as reclamações dos usuários referentes ao conforto térmico no interior das unidades habitacionais do BNH de Santos, construído em 1969, identificando quais eram os principais problemas térmicos ocorridos nestas unidades habitacionais. O objetivo desta pesquisa é verificar se os usuários encontram-se dentro dos padrões de conforto térmico estabelecidos por normas existentes e recomendar possíveis soluções que colaborem para que os apartamentos estejam dentro dos parâmetros de conforto térmico adequados. Através de relatos dos usuários, foi proposta uma medição no local cuja finalidade era identificar se havia compatibilidade entre os resultados obtidos na APO aplicada com os resultados medidos e identificar se estas compatibilidades aplicavam-se as normas de conforto térmico existentes. Simulações no software energyplus foram realizadas com a finalidade de propor melhorias projetuais nos apartamentos que estivessem em desconforto térmico. Os resultados mostram que a maioria dos usuários entende que, ao longo do ano, os apartamentos possuem temperaturas elevadas, gerando desconforto térmico. Estes desconfortos ocorrem possivelmente à ocupação de cada apartamento, além da influência da radiação solar direta que cada apartamento recebe ao longo do dia. / The current wide range of alternatives in building materials makes it possible for architects to have greater control over aspects affecting thermal comfort in their designs for social dwelling. The existence of rules governing thermal comfort parameters does not mean that dwelling units are always constructed within the optimal parameters, as this depends on the quality of projects, the correct execution of construction work, and the economic constraints of users. This study was motivated by user complaints relating to thermal comfort inside the BNH Santos dwelling units, which were built in 1969. These complaints identify the main thermal problems occurring in the dwellings units. The objective of this research is to verify whether users live within the existing standards for thermal comfort, and to recommend possible solutions so that the apartments can all be within proper thermal comfort parameters. Based on reports from users, measurements were taken on site to determine whether there was compatibility between the results obtained in the POE and the measured results, and to identify whether any compatibilities applied to existing standards of thermal comfort. Energyplus software simulations were carried out, in order to determine proposed improvements to apartments whose inhabitants were experiencing thermal discomfort. The results show that most users understand that, during the year, the apartments have high temperatures that generate thermal discomfort. This discomfort may occur as a result of the occupation of each apartment, and may go beyond the influence of the direct sunlight that each apartment receives throughout the day.
58

Avaliação do conforto térmico dos apartamentos do BNH da cidade de Santos. / Thermal comfort evaluation of social dwellings in the city of Santos.

Thiago dos Santos Garcia 05 May 2015 (has links)
Boas alternativas nas escolhas de materiais construtivos em um projeto arquitetônico possibilitam de forma mais assertiva os aspectos de conforto térmico em habitações de interesse social. A existência de normas que determinem alguns parâmetros de conforto térmico não significa que a unidade habitacional esteja dentro dos parâmetros ideais, já que dependem de bons projetos, correta execução da obra e estarem adequadas às restrições econômicas dos usuários. Esta pesquisa teve como motivação revelar as reclamações dos usuários referentes ao conforto térmico no interior das unidades habitacionais do BNH de Santos, construído em 1969, identificando quais eram os principais problemas térmicos ocorridos nestas unidades habitacionais. O objetivo desta pesquisa é verificar se os usuários encontram-se dentro dos padrões de conforto térmico estabelecidos por normas existentes e recomendar possíveis soluções que colaborem para que os apartamentos estejam dentro dos parâmetros de conforto térmico adequados. Através de relatos dos usuários, foi proposta uma medição no local cuja finalidade era identificar se havia compatibilidade entre os resultados obtidos na APO aplicada com os resultados medidos e identificar se estas compatibilidades aplicavam-se as normas de conforto térmico existentes. Simulações no software energyplus foram realizadas com a finalidade de propor melhorias projetuais nos apartamentos que estivessem em desconforto térmico. Os resultados mostram que a maioria dos usuários entende que, ao longo do ano, os apartamentos possuem temperaturas elevadas, gerando desconforto térmico. Estes desconfortos ocorrem possivelmente à ocupação de cada apartamento, além da influência da radiação solar direta que cada apartamento recebe ao longo do dia. / The current wide range of alternatives in building materials makes it possible for architects to have greater control over aspects affecting thermal comfort in their designs for social dwelling. The existence of rules governing thermal comfort parameters does not mean that dwelling units are always constructed within the optimal parameters, as this depends on the quality of projects, the correct execution of construction work, and the economic constraints of users. This study was motivated by user complaints relating to thermal comfort inside the BNH Santos dwelling units, which were built in 1969. These complaints identify the main thermal problems occurring in the dwellings units. The objective of this research is to verify whether users live within the existing standards for thermal comfort, and to recommend possible solutions so that the apartments can all be within proper thermal comfort parameters. Based on reports from users, measurements were taken on site to determine whether there was compatibility between the results obtained in the POE and the measured results, and to identify whether any compatibilities applied to existing standards of thermal comfort. Energyplus software simulations were carried out, in order to determine proposed improvements to apartments whose inhabitants were experiencing thermal discomfort. The results show that most users understand that, during the year, the apartments have high temperatures that generate thermal discomfort. This discomfort may occur as a result of the occupation of each apartment, and may go beyond the influence of the direct sunlight that each apartment receives throughout the day.
59

Conflation Of CFD And Building Thermal Simulation To Estimate Indian Thermal Comfort Level

Manikandan, K 01 1900 (has links) (PDF)
In the residential and commercial buildings, most of the energy is used to provide the thermal comfort environment to the occupants. The recent research towards Green Buildings is focusing on reduction of energy consumption by air-conditioners and fans used for producing the thermal comfort environment. The thermal comfort is defined as the condition of mind which expresses human satisfaction with the thermal environment. The human body is continuously producing metabolic heat and it should be maintained within the narrow range of core temperature. The heat generated inside the body should be lost to the environment to maintain the thermal equilibrium with each other. The heat loss from the body is taking place in different modes such as conduction, convection, radiation and evaporation through the skin and respiration. These heat losses are influenced by the environmental factors (air temperature, air velocity, relative humidity and mean radiant temperature), physiological factors (activity level, posture and sweat rate) and clothing factors (thermal insulation value, evaporative resistance and microenvironment volume). When the body is in thermally equilibrium with its surrounding environment, the heat production should be equal to heat loss to maintain the thermal comfort. The level of thermal comfort can be measured by the different indices which combine many parameters. Of these, the Fanger’s PMV (Predicted Mean Vote) – PPD (Percentage of People Dissatisfied) index was universally suggested by ASHRAE and ISO. The PMV – PPD index was derived based on the experiment conducted on acclimated European and American subjects. Many researchers have criticized that the PMV – PPD index is not valid for tropical regions and some researchers have well agreed with this index for the same region. The validation of PMV – PPD index for thermal comfort Indians has not yet been examined. The validation of PMV – PPD index can be done by the human heat balance experiment and the individual heat losses have to be calculated from the measured parameters. In the human heat balance, the convective heat transfer plays the major role when the air movement exists around the human body. The convective heat loss is dependent on the convective heat transfer coefficient which is the function of the driving force of the convection. Using Computational Fluid Dynamics techniques, an attempt has been made in this work to determine the convective heat transfer coefficient of the human body at standing posture in natural convection. The CFD technique has been used to analyze the heat and fluid flow around the human body as follows: The anthropometric digital human manikin was modeled in GAMBIT with a test room. This model was meshed by tetrahedral elements and exported to FLUENT software to perform the analysis. The simulation was done at different ambient temperatures (16 oC to 32 oC with increment of 2 oC). The Boussinesq approximation was used to simulate the natural convection and the Surface to Surface model was used to simulate the radiation. The surrounding wall temperature was assigned equal to the ambient temperature. The sum of convective and radiative heat losses calculated based on the ASHRAE model was set as heat flux from the manikin’s surface. From the simulation, the local skin temperatures have been taken, and the temperature and velocity distributions analyzed. The result shows that the skin temperature is increasing with an increase in ambient temperature and the thickness of the hydrodynamic and thermodynamic boundary layers is increasing with height of the manikin. From the Nusselt number analogy, the convective heat transfer coefficients of the individual manikin’s segments have been calculated and the relation with respect to the temperature differences has been derived by the regression analysis. The relation obtained for the convective heat transfer coefficient has been validated with previous experimental results cited in literature for the same conditions. The result shows that the present relation agrees well with the previous experimental relations. The characteristics of the human thermal plume have been studied and the velocity of this plume is found to increase with the ambient temperature. Using the Grashof number, the flow around the human manikin has been examined and it is observed to be laminar up to abdomen level and turbulent from shoulder level. In between these two levels, the flow is found to be in transition. The validation of PMV model for tropical countries, especially for Indians, was done by heat balance experiment on Indian subjects. The experiment was conducted on forty male subjects at different ambient temperatures in a closed room in which low air movement exists. The local skin temperature, relative humidity, air velocity and globe temperature were measured. The sensation vote was received from all the subjects at all the conditions. The convective heat loss was calculated from its coefficient obtained from the present computational simulation. The radiation heat loss was calculated for two cases: In case one, the mean radiant temperature was taken equal to the ambient temperature and in case two, the mean radiant temperature was calculated from the globe temperature. The other heat losses were calculated from the basic formulae and the relations given by ASHRAE based on Fanger’s assumption. From these calculations, the validity of the Fanger’s assumption was examined. The collected sensation votes and the calculated PMV were compared to validate the PMV – PPD index for Indians. The experimental results show that there was much variation in the calculated comfort level using the measured parameters and the Fanger’s assumption. For the case of mean radiant temperature equal to the ambient temperature for indoor condition, the comfort level was varying more than the actual. In addition, the calculated comfort level from the globe temperature agreed well with the comfort level from the collected sensation votes. So it was concluded that the ASHRAE model is valid for Indians if the radiation was measured exactly. Using the ASHRAE model, the required wall emissivity of the surrounding wall at different ambient temperatures was determined from the CFD simulation. In the ASHRAE model, the surrounding wall emissivity plays the major role in the radiative heat loss from the human body. Hence in recent years, research on low emissive wall paints is focused. The computational study was done to determine the required wall emissivity to obtain the thermal comfort of the occupant at low energy consumption. The simulation was done with the different ambient temperatures (16 oC to 40 oC with increment of 4 oC) with the different surrounding wall emissivity (0.0 to 1.0 with increment of 0.2). From this simulation, the change in mean skin temperature with respect to wall emissivity was obtained for all ambient temperature conditions. The required mean skin temperature for a particular activity level was compared with the simulation results and from that, the required wall emissivity at the different ambient conditions was determined. If the surrounding walls are having the required emissivity, it leads to decrease in heat/cold strain on the human body, and the thermal comfort can be obtained with low energy consumption.(please note that title in the CD is given as COMPUTATION OF REQUIRED WALL EMISSIVITY FOR LOW ENERGY CONSUMPTION IN BUILDINGS USING ASHRAE MODEL VALIDATED FOR INDIAN THERMAL COMFORT)
60

Regulace ventilovaného sedadla automobilu s ohledem na tepelný komfort člověka / Local Control of Seat Ventilation and Its Impact on Human Thermal Comfort

Matuška, Jaroslav January 2018 (has links)
Diplomová práce je zaměřena na měření ventilovaného sedadla s ohledem na tepelný komfort člověka. Popisuje a shrnuje tepelný přenos lidského těla s okolím a termoregulaci člověka. Dále zachycuje a zhodnocuje vybrané přístupy hodnocení tepelného komfortu. Zabývá se komplexním přehledem tepelně komfortních jednotek v automobilu. Představuje použitou metodu měření tepelného komfortu u ventilovaného sedadla, načež analyzuje a vyhodnocuje jednotlivá získaná data.

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