Thermal Comfort Of Room Research Articles

Investigation of flow generated by the collision of two opposed ceiling-attached jets from radial vortex diffusers

Thermal comfort in rooms with mixing air distribution systems is greatly influenced by air jets issuing from ceiling diffusers. Jets are often attached to ceilings, and as the attached jets collide with each other and generate flow, here called a merged jet, directed vertically and towards the occupied zone. In this research, air velocity and turbulence intensity were measured in the zone of the attached jets from two adjacent vortex ceiling diffusers and in the zone of the merged jet under isothermal conditions using omnidirectional anemometers. The jet characteristics, uniformity, similarity zone, spread rate, the position of virtual origin, centerline and profile distribution for velocity and turbulence intensity, were investigated in the ceiling-attached jet and the merged jet. The aim is to understand better the interactions between air jets created by diffusers and provide tools to designers of air distribution systems to estimate thermal comfort in the zone of the merged jet. Moreover, the results can be used to verify numerical models (CFD) and improve the reproduction of airflow characteristics created by diffusers. Velocity and turbulence intensity profiles show the presence of the similarity zone extending to the occupied zone, which is encouraging in terms of using well-known decay and profile equations to approximate velocity distribution, which has been done here. The draught rate index (DR) distribution in the merged jet was calculated from the measurement data. However, there is no known simple model to estimate turbulence intensity, which has a significant impact on the DR in the jet zone.

Data Driven Type-2 Fuzzy Modeling and Control of Personalized Thermal Comfort

Since the room thermal comfort has high uncertainties, it is difficult but necessary to study the modeling and control of thermal comfort. This paper tries to solve the modeling and control problem for the room thermal comfort by utilizing the temperature and humidity data collected from the working or living room. Firstly, in order to discard the noisy data and to obtain the reasonable intervals for modeling the temperature and humidity, a statistic method based preprocessing strategy is presented. Secondly, the Gaussian interval type-2 fuzzy set models are constructed to depict the personalized temperature and humidity comfort by measuring the uncertainty degrees of the obtained intervals. Thirdly, a interval type-2 fuzzy method based control scheme is proposed to realize the personalized thermal comfort regulation. Finally, some experimental results are given. And, the results show that the proposed thermal comfort models and control scheme can not only recommend a reasonable temperature and humidity range, but also can realize the optimal thermal comfort control.

Toward Utilizing IoT Open Data Set to Identify the Room Thermal Comfort

Building sectors are responsible for 33% of global energy consumption and a one-third of CO2 emission as buildings are expected to experience high performance in order to mee occupnt requirments such as lightng, coling, heting, and ventiltion systm. Internet of Things (IoT) as one of the leading developments in digital technologies led to the establishment of devices for improving the living style of the occupants. To date, stdies on intgrating the mechnisms of IoT to identify room thrmal cmfort are very sarce. Therefore, this study discussed the room thermal comfort with respect to room temperature and relative humidity. Three activities i.e. read, write, and sit were adopted. The value of air sped, metablic rate, and clohing inslation was assumed constant. The anlysis was condcted according to Fanger method and ASHRAE standard 55. Center for the Built Environment (CBE) Thermal Comfort Tool was usd to calculate the Predicted Mean Vote (PMV) vales. Results showed the average PMV values of each activity were -2.3 (read), -2.0 (write), and -1.4 (sit). Compared to the room climate data set, sitting performed the closest thermal comfort scale to the neutral. It means light activities with lower metabolic rate should be conducted in the room with higher room temperature and relative humidity.

Assessment of Thermal Comfort in Rooms Equipped with a Decentralised Façade Ventilation Unit

Thermal comfort affects not only the well-being of the occupants of a building but also the effectiveness of their learning and work efficiency. It can be disturbed if the ventilation airflow is increased when improving indoor air quality. When natural ventilation is used in the fall and winter period, the supply air temperature is low, resulting in a lack of thermal comfort. In existing buildings, there is often no place for mechanical ventilation; hence, decentralised façade ventilation units are increasingly used. The article presents an analysis of thermal comfort in rooms with this type of unit equipped with heat recovery exchangers of different efficiencies. Studies have shown that the alternating supply/exhaust airflow and the related unevenness of air streams flowing through the heat accumulator cause an inflow of low-temperature air, resulting in thermal discomfort. The highest value of the PMV index was −1.6, and the lowest was −4.1, which means that 54.8 to 100% of the occupants are dissatisfied with their thermal comfort. This means there is a need to change the construction of inlet/exhaust vents so that the stream of supply air is not directly parallel to the floor. In addition, the use of an air heater should be considered.

Reducing the cost of energy used for adaptation by using different exterior wall covering materials in Iraq

<p><span>This paper aimed to study how to reduce the amounts of heat transfer from or to the internal space of the building by covering its external walls with many locally available materials, thus reducing the rate of consumption of electrical energy used in adaptation, which leads to reducing energy consumption costs. The researcher built a model room with dimensions (1 x 1 x 2) m on the third floor of a building in Baghdad (L = 33.2 N), the dimensions of its walls (1 x 2 m) east for the installation of the sample, and the other surfaces are insulated with 200 mm polystyrene sheets. Use a 0.5 ton air conditioner to provide the room thermal comfort. The researcher found that the metal sheet with a thickness of 10 mm and covered with an insulating layer of thermoplastics is considered the best among the materials used in construction, as it saves 57% of the electrical energy consumed in air conditioning. While the use of marble, porcelain, Helen stone, and fiberglass slabs with a thickness of 10 mm, comes last because it saves less than 30% of electrical energy.</span></p>

Thermal Comfort Analysis in Rooms Using Low Temperature Convective and Radiant Heating Terminals

Abstract The concept of energy is closely related to the building sector and the systems used for heating, implicitly energy saving which is a current problem of both old and new buildings. In this paper a series of numerical simulations were made in Autodesk CFD Simulation in order to study the influence of terminal heating systems over the thermal comfort in rooms. Three case solutions were analysed, as follows: heating a room using a steel radiator, heating a room using an aluminium radiator and heating a room using underfloor heating. The values resulted through numerical simulations for the average room temperature were compared with the values for ideal heating. It was observed that underfloor heating is the most efficient source of heating among those analysed. Compared to heating using radiators, the temperatures along the length and height of the room using underfloor heating are constant and close to the ideal heating. The human body feels the most comfortable due to the uniform distribution of temperature from ground level, on height.

EXPERIMENTAL INVESTIGATION AND CFD SIMULATION OF INDOOR AIR QUALITY IN ROOM USING IMPINGING JET VENTILATION SYSTEM AT DIFFERENT OCCUPANT DISTRIBUTION

The current paper reports the analysis and design of air quality and human thermal comfort in rooms using impinging jet ventilation system at different occupant distribution. Theoretical and experimental studies at different situations of occupant distribution used the square cross sectional supply air duct with height from the foot level end (0.1h). This work presents a numerical study for predicting the indoor airflow and temperature distribution by adopting impinging jet ventilation system in office room. The emergence of the three zones flow field of an impinging jet is mostly divided into three distinguished zones: impingement zone, wall jet zone and free jet zone which produce excessive kinetic energy at the stagnation zone and distribute approximately in the longitudinal and lateral directions over the floor. Acceptable Air Distribution Performance Index (ADPI), effective temperature and ventilation efficiency were found at situations of occupant distribution (when the occupant located at the center of the room one sitting in front of the other gives optimum human thermal comfort if compared with the other situations of occupant distributions).

Passive air cooling system and solar water heater with Phase Change Material for low energy buildings in hot arid climate

Solar energy is considered alternative crucial to fulfilling the increasing of energy requirements. Passive cooling systems are considered alternatives to mechanical ventilation systems. In this work, a highlight for a solar chimney with water heater and Phase Change Material is applied as a passive solar technique for cooling building integrated with short wind tower for low energy building in the hot arid climate. This paper aims to investigate the performance of new passive air condition system with the solar chimney and solar water heater as a full system for cooling air and heating water to be applied during day and night time based on the improvement of the solar chimney in Assiut climate, Egypt. Measurements, for air temperatures and surface temperature of the aluminium and air velocity inside the chimney, water temperature and room temperature were conducted with different solar radiations to evaluate the panel performance and room thermal comfort. The findings show a minimum airflow rate in the chimney after sunset equal to 0.69 kg/s to provide fresh cold air during a hot day with a water temperature equal 58 °C and 40 °C during 2 pm and after sunset respectively. Also, integration of solar chimney and PCM with cooling wind tower achieves a significant reduction for room air temperature between 8 and 4 k during day and night time respectively and the condition within the comfort range of Predicted Mean Vote (PMV) especially night time. The results provided information to integrate this new low energy compact passive air cooling and water heating system for the housing projects of the upper floor in a hot arid climate in Egypt.

Introduction to the Dynamics of Heat Transfer in Buildings

Changing climatic conditions cause the variability of the parameters of the building’s surroundings, which in turn causes both the gains and losses of heat to change over time. There is variability in both daily and annual cycles. Meeting the requirements of thermal comfort in rooms requires maintaining the required parameters, including constant temperature. Heat gains and losses must be balanced, and this balance is ensured through appropriate heating systems. At the same time, the above means that the demand for heating buildings is not constant but depends on external weather conditions and the energy efficiency of the building. This, in turn, affects the thermal inertia, causing changes in the partition temperature to occur slower than the changes in air temperature. Therefore, the amplitude of the heating power changes is not proportional to the amplitude of the outside air temperature change. The paper presents an example of the analysis of thermal dynamics in buildings. Various aspects of heat transfer in the building were investigated taking into account the transient conditions. The variability of temperature over time at different depths of the partition was analysed, showing the results graphically. The periodic variability of the outside air temperature and the intensity of solar radiation were described by the Fourier series. Moreover, the article shows the influence of the thermal insulation thickness of the external wall on the annual amplitude of temperature changes and on the duration of the heating season, which is important from the point of view of optimization.

Cooling of office buildings in cold climates using direct ground-coupled active chilled beams

This study investigates the use of a direct ground cooling system (DGCS) using active chilled beams for the cooling of office buildings in Sweden. The methodology of the study entails laboratory experiments to develop and validate a simulation model of the cooling system. The sensitivity of the input parameters, such as borehole heat exchanger (BHE) length, internal heat gains and room temperature set point, are studied with respect to BHE outlet fluid temperature and room thermal comfort. The results provide a practical insight into designing DGCSs with regard to borehole outlet fluid temperatures. The results also show that the thermal comfort criteria in the room are met by applying the DGCS even under the most critical design conditions of undisturbed ground temperature and internal heat gains. The sensitivity study quantifies the influence of the room temperature setpoint and internal heat gain intensity on the BHE length. The BHE outlet temperature level is more sensitive in shorter BHEs than in the longer ones, and BHE length and room temperature levels are highly correlated. Thus, the sizing of DGCS can benefit from a control system to allow the room temperature to float within a certain range.

The Perception of the Indoor Environment Quality (IEQ) of Private Hostels in Ifite-Awka, Nigeria

This study aimed at evaluating the indoor environment conditions of the private hostels in Ifite Awka Anambra state with a view to establishing its quality and impacts on students dwelling on these hostels in the study area. Being a survey research, the study was affected by the use of questionnaire, literature searches and direct observations. Accordingly, a total of 311 questionnaires were administered while 258 questionnaires which represent 83% were returned and found useful. The study found that IEQ parameters of hostels in study area are: Indoor air quality was poor due to inadequate ventilation of rooms; thermal comfort of rooms was found to be warm; indoor light quality was found good and the acoustics comfort and noise slightly good and to some extent poor. Therefore, the study recommended that during the design and construction of buildings, IEQ parameters should be considered, so as to obtain a quality indoor environment.

A novel high temperature electrical storage heater using an inorganic salt based composite phase change material

AbstractWe have studied a high temperature storage heater containing an inorganic salt based composite phase change material (CPCM) for electrical load shift and operation cost reduction. The storage heater consists of CPCM modules with embedded electrical elements for charging at off‐peak hours and flow channels for discharging the stored heat in a controlled manner when needed. The flow channels are for heat transfer fluid (HTF, air in this work) to exchange heat with the CPCM modules and transport the heat to the heating space. A series of experiments are carried out to study the charging and discharging behavior of the storage heater. The effects of the flow channel arrangements between the CPCM modules, and the heating element arrangements inside the heater are studied. A mathematical model is also developed to investigate the performance of the storage heater with a focus on the performance comparison of the storage heater filled with the CPCM and that with the ferric oxide bricks (the conventional sensible heat storage material), and the evaluation of temperature control strategy for the CPCM based storage heater. The results show that a charge of 8 hours of the storage heater during the off‐peak period is sufficient to supply heat for the whole day under the conditions of this work. The flow channel arrangements have significant influences on the storage heater performance in terms of temperature distribution of the CPCM modules and HTF outlet temperature, and the efficiencies of the charging and discharging processes. An interlaced arrangement of CPCM modules in the heater can effectively reduce the temperature swing (eg, between 21.7°C and 22.5°C over a day) and hence improve the room thermal comfort level. The results also show that the CPCM based storage heater gives a superior performance than the ferric oxide based storage heater. Given the storage volume, the power rating, and the amount of stored heat, the mass of the ferric oxide based storage heater is more than 1.6 times that of the CPCM based storage heater. Given the mass and power rating, the heat storage capacity of the CPCM based heater is nearly 68% higher than that of the ferric oxide based storage heater. It is also found that the heat storage performance could be enhanced through a temperature control strategy with the temperature measurement located 15 mm away from the heating elements, for which the heating elements only need two start‐stops over the 8‐hour charging period.

Thermal Comfort Identification of Traditional Bugis House in Humid Tropical Climate

This study aims to determine the thermal comfort conditions in the interior of traditional Bugis houses in South Sulawesi. This phase measured 18 (eighteen) houses by collecting data on 2 (two) main variables of room thermal comfort, namely air temperature and relative humidity. The recording time starts from 08.00 to 16.00 WITA. Observation made to collect room geometry data, building orientation, roof slope, and material used. Measuring instruments are placed in the living room throughout the room. The analysis carried out on the measurement data is then correlated with the observation. The results show that the average outside temperature above the thermal comfort standard is around 32.0 to 37.4℃ from morning to afternoon, the maximum temperature reaching 41.7℃ occurs around 13.00 to 14.00 WITA and the minimum temperature is 28.2℃ only occurs in the morning. Air humidity average is relatively fair in the thermal comfort zone between 42.8 to 69.8%. Material gives the most dominant influence on heat induction from the outside environment to the interior space. The orientation of the house found in North-South is hotter, the roof with a double slope is hotter, and the lower the ceiling is more hot.

Aluminum Coated Micro Glass Spheres to Increase the Infrared Reflectance

The reflective properties of micro glass spheres (MGS) such as Solid Micro Glass Spheres (SMGS, “glass beads”) and Micro Hollow Glass Spheres (MHGS, “glass bubbles”) are utilized in various applications, for example, as retro-reflector for traffic road stripe paints or facade paints. The reflection behavior of the spheres can be further adapted by coating the surfaces of the spheres, e.g., by titanium dioxide or a metallic coating. Such coated spheres can be employed as, e.g., mid infrared (MIR)-reflective additives in wall paints to increase the thermal comfort in rooms. As a result, the demand of heating energy can be reduced. In this paper, the increase of the MIR-reflectance by applying an aluminum coating on MGS is discussed. Aluminum coatings are normally produced via the well-known Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD). In our work, the Liquid Phase Deposition (LPD) method, as a new, non-vacuum method for aluminum coating on spherical spheres, is investigated as an alternative, scalable, and simple coating process. The LPD-coating is characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and reflection measurements. The results are compared to a reference PVD-coating. It is shown that both sphere types, SMGS and MHGS, can be homogeneously coated with metallic aluminum using the LPD method but the surface morphology plays an important role concerning the reflection properties. With the SMGS, a smooth surface morphology and a reflectance increase to a value of 30% can be obtained. Due to a structured surface morphology, a reflection of only 5% could be achieved with the MHGS. However, post-treatments showed that a further increase is possible.

О КАЧЕСТВЕ НОРМИРОВАНИЯ ТЕПЛОЗАЩИТЫ ЗДАНИЙ

Considered relevant the problem of quality regulatory documentation for thermal protection of buildings, not only depends on the quality of the thermal protection designed buildings but also ensuring favourable hygienic conditions in the premises, as well as reliability and cost of enclosing structures. Provides a critical analysis of existing regulations on heat-shielding of buildings for compliance with the requirements of technical regulations on safety of buildings and constructions (FZ 384)-creation of thermal comfort indoors and ensure constructive reliability of external walling during the cold period of the year. It is noted that the existing regulations on heat shielding buildings incorrectly defined the main objective of the thermal insulation of buildings. How to ensure a given level of heat energy consumption. Critically analyzed the main sections of the existing regulations and proposed methods of Thermo-physical parameters of rationing of exterior fencing of buildings in which priority is energy conservation and ensuring thermal comfort in rooms, the main criterion which is established by specialists the difference between the room temperature and the temperature of the inner surface of the outer fence. Offered a simple and reliable technique for regulation of water resistance design that provides no moisture accumulation in constructions during the cold period of the year. The technique of integrated calculation of heat and vapor barrier layers of multilayer enclosing structures, Thermo-physical properties which meet regulatory requirements

Numerical Investigation of Energy Saving Characteristic in Building Roof Coupled with PCM Using Lattice Boltzmann Method with Economic Analysis

Due to their characteristics of high energy storage density and a nearly constant melting temperature, phase change materials (PCMs) could be inserted into the roof of green buildings in order to reduce the energy consumption and ameliorate the room thermal comfort. In this paper, an enthalpy based multiple-relaxation-time (MRT) lattice Boltzmann method (LBM) was developed to calculate the transient phase change conjugate heat transfer with solar radiation inside the green building’s PCM roof in the hot summer and cold winter areas of China. The effect of the PCM melting temperature on the variation of the roof internal temperature was investigated and the energy saving characteristic of the PCM roof under an intermittent energy utilization condition was also analyzed by comparing with the performance of the roof filled with sensible insulating materials (SIMs). Then, the life cycle incremental costs and incremental benefits of a PCM roof and SIM roof were studied by using the comprehensive incremental benefit model so that the green building roof could be economically evaluated. The results indicate that a temperature rise inside the roof during summer cooling time could be delayed due to the latent heat of the PCMs. It was also found that the melting temperature and the thickness of the PCM layer should be chosen appropriately for enhancing the energy saving amount of a PCM roof. Based on this, the PCM roof could have a better energy saving capability than the SIM roof. During the winter heating time, as the environment temperature and the room temperature are both below the PCM melting temperature, the PCM roof does not have a latent heat characteristic so that it performs like a SIM roof. Furthermore, due to the high price of PCMs, the incremental cost of green building is increased, which makes the PCM roof have a negative comprehensive incremental benefit. Under this circumstance, developing PCMs with a low price and stable chemical properties is a key scientific bottleneck for a wider application of PCM roofs in the architecture engineering field.

Influence of Iwans on the Thermal Comfort of Talar Rooms in the Traditional Houses: A Study in Shiraz, Iran

In traditional buildings many climatic strategies have been used to provide indoor thermal comfort in south and central parts of Iran. A common element is called an iwan. This study investigates the indoor thermal comfort of a room adjoined to a talar in a traditional house which has an iwan, in Shiraz, Iran. The data related to the temperature and relative humidity of the room are used to calculate the thermal comfort index of PMV (Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied) by considering the following two cases: a talar room with an iwan and one without an iwan, by means of DesignBuilder software. For the purpose of validation, the air temperature and relative humidity of the talar room with an iwan were measured over 10 days and compared to the results of the simulation. Having a valid simulation, computation was conducted for the selected house in various cases for an annual passive operation of calculating PMV and PPD. The numerical results revealed that the talar room adjoined to an iwan located in the south front of the courtyard had relatively good conditions during the hot months, including June and July. In addition, it could provide fully satisfactory comfort conditions during August and September. According to the results, it is found that the iwan makes a talar room 62% more desirable for the hot months in comparison with a talar room without an iwan.

Assessment of Thermal Comfort in a Building Heated with a Tiled Fireplace with the Function of Heat Accumulation

Thermal comfort determines the state of satisfaction of a person or group of people with thermal conditions of the environment in which the person or group of persons is staying. This state of satisfaction depends on the balance between the amount of heat generated by the body’s metabolism, and the dissipation of heat from the body to the surrounding environment. Due to differences in body build, metabolism, clothing etc. individuals may feel the parameters of the environment in which they are staying differently. Therefore, it is impossible to ensure the thermal comfort of all users of the room. However, properly designed building systems (heating, ventilation, air conditioning) allow for creating optimal thermal conditions that will evaluated positively by the vast majority of users. Due to the fact that currently we spend even 100% of the day indoors, the subject becomes extremely important.The article presents the evaluation of thermal comfort in rooms heated with a tiled fireplace with the function of accumulation of heat using the PMV (Predicted Mean Vote) and PPD (Predicted Percentage Dissatisfied) indices. It also presents the results of studies, on the quality of the micro-climate in such spaces. The system of heating premises described in the article is not a standard solution, but is now more and more commonly used as a supplement to the heating system, or even as a primary heating system in small objects, e.g. single-family houses, seasonal homes, etc. The studies comprised the measurements and analysis of typical internal micro-climate parameters: temperature, relative humidity and CO2 concentration. The results obtained did not raise any major reservations. In order to fully assess the conditions of use, the evaluation of thermal comfort of the analyzed rooms was made. Therefore, additionally the temperature of radiation of the surrounding areas, and the insulation of the users’ clothing was determined. Based on the data obtained, the PPD and PMV indices were determined according to EN ISO 7730: 2005 Ergonomics of the thermal environment - Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria [1]. The obtained PMV values did not fit within the limits of thermal comfort, and the percentage of people dissatisfied reached almost 20%.

Increasing natural ventilation using solar chimney

At a time when much attention is paid to the problem of energy saving is looking for new technical solutions, among others in the construction industry. At present, searching new solutions is a worldwide trend in creating buildings. Those solutions enable a comfortable use of building structures in harmony with natural environment and ensure reducing energy consumption. Solar chimneys, which facilitate the gravity ventilation by using solar energy, may be a solution to the problem. In hot climates solar chimney has been applied in the process of passive cooling of a building. In temperate zones and cold is used to assist natural ventilation. The problem of the solar chimney is not popular in Poland. Construction in Bydgoszcz two research positions, enabled the analysis of the impact of solar chimneys on the thermal comfort of rooms. This article presents experimental studies on solar chimney located in Poland. The analysis of the flow of air in the room during the day have been measured using two testmodels situated on the 3.1 building of UTP University of Science and Technology at 7 Kaliska street in Bydgoszcz.

A newly composed paraffin encapsulated prototype roof structure for efficient thermal management in hot climate

For efficient thermal management in the building under hot weather condition a new paraffin composition as suitable PCM is needed. Several notable attributes of paraffin wax including thermo-physical properties, open air atmospheric condition, economy, and environmental amiability make them suitable PCM for incorporation in the building. Thus, new PCM with massive storage of heat or cold in a specific volume is demanded. Iraqi local paraffin waxes as PCM are proven to be highly prospective due to their high-vitality thickness and isothermal conduct. However, thermal performance optimization of new PCM is pre-requisite to determine its effectiveness in hot climate location. We prepare three new PCM compositions with different oil to wax ratios from the crude petrochemical feed stock waste using fractionation followed by de-waxing and crystallization. The melting temperatures and flash points of these paraffin waxes are ranged between 19 and 44 °C and 177–256 °C, respectively, which upon encapsulation in the prototype roof construction are demonstrated to produce thermal comfort in rooms under hot climate (Iraq). Furthermore, these indigenous PCMs (local paraffin) are abundant, environmental friendly, economic and save electricity cost and HVAC (heating-ventilating air conditioning) systems. Experimental results displayed much reduced temperature fluctuation and internal heat flux of the prototype room than the commercial PCMs. Temperature profiles and solar irradiances inside the room on hot summer days in Bagdad showed remarkable electricity saving. This newly extracted PCM being non-flammable and thermally comfortable are truly secure for buildings construction worldwide.