Ceiling System Research Articles

Evaluation of Using the Ceiling and Wall Spots Ventilation System on Indoor Thermal Environment

The aim of this paper is to enhance the local comfortable zone for the occupants in a small office room. The ceiling spot ventilation (CSV) system and the wall spot ventilation (WSV) system are proposed and investigated numerically to show the influence of these systems on the local thermal comfort and energy demand. Three different amounts of airflow rate are used in this investigation. A CFD model is employed to explain the behavior of indoor airflow and temperature distribution in each case study. The results show that, when using these systems as a main ventilation system will reduced the demand on fresh air and this will reduce the required load on cooling coil and saving more energy. Also, the results revealed that the wall spot ventilation (WSV) was provided a required local indoor thermal environment air for the occupant zone. Therefore, using this system will provide a comfortable local environment and enhance the air velocity distribution as well as saving more energy.

Rehabilitative training system based on a ceiling rail for detecting the intended movement direction of a user.

BACKGROUND:Accurate detection of the intended movement direction of a patient plays an important role in the development of a training system for gait rehabilitation and enables to increase the effect of gait rehabilitation training.OBJECTIVE: This study investigated the detection of the intended movement of a user to operate a ceiling rail-based rehabilitative training system with accurate timing.METHODS: To detect the movement direction intention of a user, two potentiometers were used to measure the movement direction in the anterior, posterior, and left and right directions of the user when operating the driving motor of the rehabilitative training system. A simple test mock-up with two potentiometers was fabricated, and the experiments were conducted to determine the effect of the direction of movement on the measured values of potentiometers. A direction measurement algorithm was developed to control the driving motor of the rail-based gait rehabilitative training system.RESULTS: The intended movement direction of the user could be predicted for eight directions by combining the “positive value, 0, negative value” of each measured value of the two potentiometers. Further, the developed algorithm was effectively used to control the driving function to assist the walking, sitting–standing, and climbing up–down the step activities in daily life.CONCLUSIONS: The movement intention detection function for users developed in this paper can be used to effectively control a rehabilitative training system for patients with hemiplegia to improve gait movement and posture balance, thereby improving their function of activities of daily living.

Energy and Exergy Performances of Floor, Ceiling, Wall Radiator and Stratum Ventilation Heating Systems for Residential Buildings

To provide a highly efficient heating for the residential buildings, different heating systems, including the floor and ceiling heating, wall radiator heating and stratum ventilation heating, are compared based on a typical sleeping environment in this study. Performance indices, including occupied zone predicted mean vote (OPMV), energy consumption and exergy consumption, are analyzed under different conditions. The results show that stratum ventilation heating performs better than the conventional floor, ceiling and wall radiator heating in terms of energy and exergy consumptions. Firstly, under stratum ventilation heating, the OPMV equals zero at a low supply air temperature (20.0°C for stratum ventilation heating at the supply air angle of 45° and 19.7°C for stratum ventilation heating mode at the supply air angle of 75°). Secondly, stratum ventilation heating consumes less energy than the floor, ceiling or wall radiator heating of identical OPMV increments. In addition, compared with the floor, ceiling, wall radiator heating and stratum ventilation heating at the supply air angle of 45°, the energy-saving ratio of stratum ventilation heating at the supply air angle of 75° reaches 29.7%, 21.2%, 22.4% and 4.2% respectively when OPMV equals zero. Lastly, for stratum ventilation heating, the supply and return water temperatures in the air handling unit are significantly lower. Therefore, a lower exergy consumption is realized under stratum ventilation heating in comparison with the conventional floor, ceiling and wall radiator heating.

A novel operating strategy to avoid dew condensation for displacement ventilation and chilled ceiling system

Avoiding dew condensation on chilled ceiling is crucial for the application of displacement ventilation and chilled ceiling systems. Comparison with the conventional operating strategy, a novel operating strategy is proposed to control the humidity ratio of air near ceiling. When operating, chilled ceiling is closed at the initial stage and will be opened by verifying that the dew point temperature of the air near ceiling is 2 K lower than the operating temperature of ceiling surface. Different options to shorten the time of initial stage were investigated by simulation including raising the flow rate of the supply air and decreasing the humidity ratio of ventilation. Results show that the phenomenon of dew condensation on the displacement ventilation and chilled ceiling system can be alleviated with this strategy. With the optimization of supply air parameters the time of preparation process can be shortened to 180 s. This study provides a novel insight of optimization for displacement ventilation and chilled ceiling systems, which may become an important approach for preventing chilled ceiling from condensation.

A field study of occupant thermal comfort with radiant ceiling cooling and overhead air distribution system

This paper presents the findings of a field research on occupant comfort with radiant ceiling cooling and overhead dedicated outdoor air system (RCF). This extends a previous thermal comfort study with radiant cooling and intended to investigate the actual occupant thermal comfort with radiant ceiling cooling and overhead air distribution system. The research is based on a revised ASHRAE RP-921 project protocol with a combination of field measurements and questionnaires. A total of 135 sets of data from 44 participants were collected in summer. The results show that occupant whole-body thermal sensations with the radiant ceiling and overhead air system had deviated from the PMV model at the 23.6~28.6 °C operative temperature (OPT) range in the summer. The main advantage of the RCF system for thermal comfort was found to be better comfort conditions than with conventional air conditioning at the same operative temperature range. The results of this study showed that the neutral temperature with the RCF is around 26 °C; the preferred temperature by occupants was around 25.3 °C with the RCF. The calculated Predicted Percentage Dissatisfied (PPD) rate is 13.9%, but the actual thermal environment dissatisfaction rate was 8.3% with an unacceptability rate of only 1.5%, which is substantially better than the calculated PPD rate. The study results were compared to earlier findings and validated against some important results, providing benchmarks for future work.

Investigating the vibration properties of integrated ceiling systems considering interactions with surrounding equipment

SummaryStudies on recent earthquakes highlighted that buildings with minimal structural damage still suffer from extensive damage and failure of nonstructural components. The dropping and damage of suspended ceiling systems, which typically consist of acceleration‐sensitive nonstructural elements, resulted in lengthy functional disruptions and extended recovery time. This article experimentally and analytically examined the vibration properties of an integrated ceiling system considering the interactions with surrounding electrical equipment. The theoretical stiffness and corresponding frequency of electrical equipment were initially derived and then verified by subsequent vibration tests and numerical analyses. The seismic performance of the air conditioner (AC) was evaluated with different installment configurations based on design spectra and floor response spectra. Vibration tests of the suspended integrated ceiling system considering the interactions with surrounding equipment showed that the inclusion of peripheral constraints increased the first horizontal vibration frequency of the ceiling system by a factor of approximately 6. The natural frequencies of all components in the integrated ceiling system were almost identical, which was attributed to the coupled behavior between the ceiling panels and surrounding equipment, emphasizing the effect of interactions between adjacent components during dynamic analysis. Based on the above experimental investigation, an associated numerical model of the integrated ceiling system was created. Finally, corresponding parametric studies that included the interactions with surrounding equipment, reinforcing braces of ACs and strengthening members at the rise‐up location between two elevations were performed.

Simulation of hybrid GSHP systems utilizing radiant ceiling terminal and system evaluation with analytic hierarchy process method

Hybrid ground source heat pump (GSHP) systems which utilize capillary radiant ceiling are promising to provide a better building comfort while reducing energy consumption. We have developed a GSHP model and an analytic hierarchy process (AHP) method for evaluating the system feasibility. The hybrid GSHP system provides heating/cooling for an office in Wuhan, China. A conventional HVAC system – water chiller + gas boiler (WB) system was also simulated. The results showed that the hybrid system would provide a better indoor comfort and remains at the thermal comfort class I, and the hybrid system would incur a 14.5% lower cost but would provide 43.2% more energy saving. The hybrid GSHP system could reduce 20.23 tons of CO2 emission, while 1.39 tons more SO2, 0.39 tons more NOx and 9.70 tons more Ash emissions could be produced. Overall, the hybrid system performance evaluation result (SPER) was 0.966, and the WB system was 0.746. These SPERs were quantified system evaluation results calculated using the AHP method, which have considered the impacts of the various factors – economic cost, energy saving and environmental impact. The hybrid GSHP system is more adaptable than the WB system and has a good application prospect in this climate region.

Assessment of the performance of airflow in an operating rooms using ceiling supply and sidewall inlet systems

Poor air quality arises by and large from inadequate ventilation and presence of contaminants. In particular to hospital environments, it exercises direct and significant influence over infections occurrence. The purpose of this paper is to research, through computational fluid dynamics, how ceiling (four-way supply) and sidewall (conventional high supply) inlets systems, as well as outlet (exhaust) positioning, effect air motion and distribution in operating rooms. By the assistance of numerical modeling, four alternative scenarios of a operating room were investigated, maintaining flow rates and varying inlet system and outlet position. The results are presented in terms of velocity vectors and temperatures, which were compared to the experimental data available. Subsequently, a qualitative analysis regarding conformity to sanitary requirements was conducted.

A study on influencing factors for simplified seismic collapse risk assessment of steel moment-resisting frames with intermediate ductility

Purpose Mid-rise steel moment-resisting frames (MRFs) with intermediate ductility are a major part of conventional residential buildings in Iran. According to Iranian seismic design codes, in this resisting system, considering the strong-column/weak-beam (SCWB) criterion is not mandatory. Where a metal deck ceiling system is used, the composite action of a concrete slab and steel beams could change the collapse mechanism of the structure, especially in the MRFs with intermediate ductility. The purpose of this paper is to investigate the influence of the composite action in the seismic collapse risk of this type of structures. Seismic collapse risk assessment can be carried out by using simplified pushover-based methods. In these methods, the cyclic deterioration of an equivalent single degree of freedom (ESDoF) system must be considered when the modified Ibarra–Medina–Krawinkler is used for nonlinear modeling of MRFs. Accordingly, a modified method is developed to use in simplified collapse risk assessment process. For these purposes, two mid-rise MRFs with intermediate ductility located in Tehran have been selected as case studies. The results confirm that the composite action is very effective in collapse risk value in the steel MRFs in which their SCWB ratio is less than 1. Moreover, the proposed approach of considering the cyclic deterioration of ESDoF systems increases the accuracy of the simplified collapse assessment approaches. Design/methodology/approach Identifying seismically vulnerable buildings to collapse requires using robust methods. These methods can be simplified based on pushover analysis methods. An attempt was made to apply one of these approaches for steel MRFs with intermediate ductility. In these frames, the composite action of a concrete slab and steel beams could change the collapse mechanism. Here, two MRFs were investigated in order to assess this effect on collapse risk value. This process was done by modifying the SPO2IDA method as a simplified collapse capacity evaluation approach by developing a relationship to consider the cyclic deterioration effects for the ESDoF systems. Findings The results showed that it is necessary to consider the slab effects in the analytical model in the collapse assessment process of MRFs with intermediate ductility, especially in the condition in which the SCWB ratios of the frame are less than 1. Furthermore, by utilizing the proposed method of considering the ESDoF cyclic deterioration, the error values of the SPO2IDA program were reduced significantly. Moreover, estimating the collapse risk parameters shows that the utilized simplified method presents suitable accuracy and could be an acceptable approach to collapse risk assessment of mid-rise steel MRFs. Originality/value The influence of the composite action in seismic collapse risk of MRFs with intermediate ductility is investigated. Also, a modified relationship is developed to consider the deterioration effects on the ESDoF parameters used in simplified collapse risk assessment process. Also, a framework is presented for utilized methodology.

A Discussion on the Introduction of the Price Ceiling System on the Newly Built Apartment

최근 일부지역의 주택가격이 상승하는 조짐을 보이자 정부는 사실상 폐지 상태였든 민간택지에 대한 분양가상한제를 다시 도입하는 방안을 발표하였다. 민간택지에 분양가상한 =제를 적용하는 것에 대해서는 논란이 많다. 정부는 분양가상한제를 통하여 주택가격안정을 달성할 수 있다고 주장한다. 반면 반대하는 견해는 장기적으로 주택공급을 감소시켜 주택 가격상승을 야기하다고 주장한다. 분양가상한제가 법적정당성을 인정받기 위해서는 우선 해당 법제도가 추구하는 목적이 정당하여야 하고 적합성, 필요성, 균형성 및 법치국가원리 의 명확성을 갖추어야 한다. 헌법상 우리나라의 경제질서는 시장경제를 원칙으로 하면서도 사회정의를 실현하기 위하여 국가가 규제와 조정을 하는 체제이다. 주거안정이 갖는 중요성을 감안할 때 분양가상한제를 통하여 추구하는 목적은 정당하다. 근래 일부지역의 주택 가격이 상승한 주된 원인은 정부가 경기부양을 위해 채택한 저금리에 근거한 신용량의 대량공급이다. 주택가격안정의 주된 수단은 이자율 및 신용량이 되어야 하고, 분양제상한제는 하나의 보조적 수단에 지나지 않는다. 분양가상한제가 주택가격안정에 미치는 효과는 검증되지 않고 있다. 신규주택의 분양가격이 기존 주택가격에 미치는 영향은 제한적이다. 분양 가상한제의 효과를 높이고 부작용을 보완하기 위해서는 분양가격 산정기준의 보완이 필요하다. 분양가격은 단순한 건축원가 뿐 만 아니라 판매 및 관리비, 지급이자, 사업주체의 이익 등이 모두 포함된 것이다. 법령의 취지로 보면 판매 및 관리비, 지급이자, 사업주체의 이익 등은 기본형건축비에 포함되고, 건축비가산비용이나 주택비가산비는 실제 공사원가를 의미하는 것으로 보인다. 그렇다면 기본형건축비를 구성하는 중요 항목 및 세부기준을 공개하여 그 적정성을 검토하고, 사업주체가 분양가격을 예상할 수 있도록 하는 것이 바람직하다. 사업주체의 적정한 이익은 보장되어야 하며 그 수준에 대해서는 사회적 합의가 필요하다. 분양가격을 구성하는 건축비가산비용이나 택지비가산비는 예상공사비이므로 실제 공사원가와는 차이가 클 수 있다. 예상공사비와 실제 공사원가의 차이가 클 경우 분양가상한제의 효과는 낮아진다. 분양가상한제의 취지를 달성하기 위해서는 이들 비용에 대해서 세밀한 기준을 마련하고 심사를 엄격하고 통일적으로 운용할 필요가 있다.Recently the government announced that the price ceiling system on the newly built apartment, which in reality abolished, would be introduced. The price ceiling system on the newly built apartment is a highly controversial topic. The government assert that it will cause housing prices falling, but opponents assert that in long- term it will cause housing prices rise because of supply decrease. To acquire legal justification, the goal of the system should be just and it should be suitable, necessary, balanced means. Our economic system is fundamentally based on free market system, on the same time the government can control and adjust the economy to achieve social justice. Considering the importance of housing price stability, the goal of the system is conceded as just. The primary cause which leaded to rise of housing price recently is low interest rate and the resulting expansion of credit. Therefore the policy which pursuing stability of housing price should focus on interest rate and credit. The system is only accessorial means. The effect of the system is not verified. To heighten an effect and to minimize side effects of the system, it is needed to supplement the standard for price calculation. Cost of standard apartment building includes construction cost, a dministrative cost, interest, profit. So it is desirable to open standard in detail for important items and to get a consensus on the level of profit. Additional construction cost and additional land cost are only expected cost which differ from actual cost. To achieve the goal of the system, it is needed to control these additional cost much more tightly.

High-Rise Social Housing in Hot-Humid Climates: Towards an ‘Airhouse’ Standard for Comfort

The pressure to provide social housing in a fast and economic way, as well as outdated regulations, constrain the design of these buildings, having serious implications for the comfort of occupants and the environment. This becomes more critical in hot-humid climates, such as Malaysia, with uniformly high temperature and humidity and low wind speeds. In its capital, Kuala Lumpur, an extensive program of construction for high-rise social housing is being carried out, however, shortly after the flats are occupied, or as soon as they can afford it, the residents fit wall mounted air conditioning units. This research started by looking at Malay vernacular architecture and the traditional strategies for ventilation and cooling. After a review of current building regulations and green tools employed in the country, two campaigns of fieldwork were carried out to assess the actual indoor and outdoor thermal and air quality conditions in the buildings, which were found to be inadequate for both the local regulations and international recommendations. The fieldwork also allowed the identification of the critical design issues to address. A ventilation and filtering ceiling system has been identified as one of the possible solutions for the current situation and has been tested through physical and computer models. The system improves comfort by reducing the air temperature, humidity, and amount of airborne particles and gases, as well as constantly providing an adequate airflow rate. It is the first attempt to develop what we have named the ‘airhouse’ standard for tropical countries.

Evaluation of Radiant Heating Ceiling Based on Energy and Thermal Comfort Criteria, Part II: A Numerical Study

Large-surface radiant heating ceiling systems favor energy-efficient solutions on the heat generation side because of the relatively low temperature of the heat transfer medium. Additionally, their application in the renovation of existing buildings is relatively uncomplicated and requires minimal changes to the building’s construction. However, ASHRAE Standard-55 and former studies by Fanger indicated that among large-surface radiant systems, the highest percentage of dissatisfaction for an equal radiant temperature asymmetry (RTA) was reported for a warm ceiling. The maximum RTA of 4 K corresponding to 5% of dissatisfaction was suggested. In the first part of our study (subjective experiments), we have suggested the RTA of about 7.4 K if occupants have winter clothing (Safizadeh et al., 2018). However, former studies tested radiant ceiling systems at different temperatures in “neutral conditions” with a constant operative temperature, which rarely occurs in reality. Accordingly, the goal of this study is to evaluate the potential application of low-temperature radiant heating ceilings in a building with low- and high-performance facades using steady-state simulations with a coupled CFD–thermal comfort model and transient simulations using TRNSYS. Forty combinations of simulation scenarios including six ceiling surface temperatures (20 °C, 25 °C, 28 °C, 33 °C, 38 °C, and 45 °C), two low- and high-performance facades, two rooms with one and two facades, and distances of 1 m and 3 m to the window were examined. The findings of this research show that the supply water temperatures between 28–45 °C from a heat pump are ideal for a building with a high-performance façade. Additionally, the results suggest that ceiling temperatures as low as 20–25 °C in renovated buildings and 25–28 °C in a building with low-performance facades can provide optimal thermal sensations at most body parts. This study also proves that the PMV comfort model (Predicted Mean Vote index) is not at all a suitable model for the evaluation of radiant heating systems (especially if occupants have winter clothes), even if the air/operative temperature distribution near an occupant is uniform.

Collaborative optimization of ground source heat pump-radiant ceiling air conditioning system based on response surface method and NSGA-II

A parametric collaborative optimization method for ground source heat pump-radiant ceiling (GSHP-RC) system is proposed to find the optimum setpoint combinations by maximizing system performance and reducing operating costs while ensuring indoor thermal comfort. The method integrates response surface method (RSM) and fast non-dominated sorting genetic algorithm (NSGA-II) to search the nonlinearity relationship between the controllable factors and the response factors and execute multi-objective optimization (MOO) progressively. A GSHP-RC system in an office building is investigated based on TRNSYS. Three controllable factors, the water supply temperature of radiant ceiling, the indoor set temperature and the water supply temperature of the heat pump, were used to analyze the influence mechanism on the system. The system performance, thermal comfort and economy are evaluated by seasonal performance factor (SPF), predicted mean vote (PMV) and the operating cost (OC). Two optimal cases were determined with the SPF of 3.741 and 3.734, the OC of CNY 23525 and 24613, and the PMV of 0.225 and -0.223 respectively. The optimization can realize 17.3% and 13.0% of the operating cost saving for the optimal cases respectively with the significant improvement in SPF under the premise of indoor thermal comfort compared with the reference case with conventional parameters.

Identification of Dynamic Characteristics and Numerical Analysis of Ceiling System Considering Collision Adjacent Structures

Identification of Dynamic Characteristics and Numerical Analysis of Ceiling System Considering Collision Adjacent Structures

A computational model of an improved cooling radiant ceiling panel system for optimization and design

Radiant cooling system comes to the foreground recently due to its improved thermal comfort and energy saving potential. However, surface condensation is still an unsolved problem and hinders the application of radiant cooling systems especially in hot and humid areas. An inside air layer was introduced to the improved cooling radiant ceiling panel (CRCP) system to achieve uniform temperature distribution on panel surface and reduce water condensation risk. A computational model for heat transfer analysis of the improved CRCP system was established and verified with experiment. The effects of the thickness of aluminum sheets, cooling panels and air layer, as well as the diameter and spacing of copper pipes on cooling capacity of the new system are studied. It is shown that the cooling capacity increases with thicker aluminum sheet and thicker radiant panel but thinner air layer. A thickness of 4.0–5.0 mm for the cooling panels is recommended to achieve a uniform surface temperature distribution according to numerical simulations. Besides, copper pipes with small diameter and thin plastic join are both beneficial to system performance. This study also provides a method to evaluate the maximum temperature difference and lowest surface temperature of the whole cooling panel, as well as a simple design chart for the improved CRCP system. Moreover, it is feasible to enhance the flow disturbance in air layer to improve heat transfer between the aluminum sheets and cooling panels, which can contribute to the savings of initial investment by using less pipe materials in CRCP.

Numerical and experimental study on the characteristics of radiant ceiling systems

ABSTRACTInsufficient knowledge about characteristics of radiant systems has caused problems in the wider application of the radiant system, such as water condensation, bad thermal comfort, etc. In this study, key characteristics of a radiant system in terms of an inherent relationship between total heat flux and surface temperature were analysed. General models for describing such the relationship were developed and validated by elaborate experimental data. Operation limit region of the radiant system was identified and proposed by plotting key parameters in one surface, including supply water temperature, operative temperature panel surface temperature as well as total heat flux density. It was found that not all of the points within the operation limit region were suitable for practical application in order to avoid water condensation risk in cooling mode and large temperature differences in a vertical direction in heating mode. Evolved forms of operation limit regions for cooling and heating applications were put forward and their characteristics were addressed. The results reported in this paper could help manufacturers as well as engineers to better design, configure and regulate radiant systems for better product development and improved indoor thermal comfort.

Seismic demand and capacity assessment of suspended ceiling systems

In recent years, scientific interest for the study of Non-Structural Elements (NSE) has significantly increased and the importance of the seismic safety of these elements has become a widely discussed topic. Several technologies able to guarantee the seismic safety of NSE were created. In particular the sector of suspended ceiling has seen the development of different systems for achieving this purpose. Specific internal joints between profiles, perimeter brackets and bracing systems have been created to realize “anti-seismic” suspended ceilings. Several shake table tests, also defined qualifying tests, have been performed to analyze the behaviour of these systems.This work presents new original studies on seismic behaviour of suspended ceilings with an experimental fragility approach. Recently cyclic quasi-static tests have been realized at the University of Padova by means of a specifically developed experimental setup. First, experimental results were processed to define the hysteretic capacity curves of a typical metal T-Grid suspended ceiling. Then, these curves were exploited by means of numerical analyses to determine the elastic and inelastic response of the suspended ceiling installed at various levels of five multi-storey frames characterized by different vibration periods. Linear dynamic analyses of the frames subjected to 7 spectra-compatible artificial seismic signals were performed to obtain floor acceleration signals and spectra. Then three alternative numerical approaches were employed to define the seismic demand on the suspended ceiling. Using a displacement-based approach, capacity curves and elastic floor spectra were compared in the ADRS (Acceleration Displacement Response Spectrum) domain to evaluate the elastic displacements and accelerations of the suspended ceiling (Spectral Analysis). Also, Linear and Non-Linear Time-History analyses of the NSE were performed according to a cascade approach. The comparison of the seismic demands resulting from elastic, inelastic and spectral analyses is reported in the paper for each of the frames.

Efficacy of high-performance ceiling systems

A current approach to try to solve a low frequency impact-induced structure-borne noise issue in lightweight woodframe buildings has been the application of a resilient ceiling suspended by one-inch deflection spring hangers. While this system has been lab tested it was only compared to an assembly with no isolation in which the gypsum board was directly attached to the bottom of the joists. The authors have repeated the testing of one-inch deflection ceiling hangers in the same lab but this time they compared it to the same isolators with the springs removed, standard resilient sound clips and other ceiling isolation systems. Relative performance differences of the isolation systems will be presented along with transmissibility, static stiffness, dynamic stiffness and damping measurements of each isolation element. A few theories as to why the systems behave the way they do will also be presented.

Finite Element Modelling of the Structural Behaviour of a Novel Cellular Beam Non-composite Steel Structure in Fire

A novel cellular beam structure (CBS) intended for two to ten storey office buildings has been developed by the Southern African Institute of Steel Construction (SAISC) which consists of prefabricated modules comprising of cellular steel beams encased in a multi-layered flooring system, which yields an innovative structure with many benefits, including reduced construction time and cost. However, a major obstacle to commercialisation is the unknown fire resistance. Thus, this paper presents a series of non-linear finite element models that simulate the structural behaviour of the CBS under standard and parametric fire conditions. The simulations include single structural elements in isolation and global structure models. Overall, it was found that the CBS performs satisfactorily in a fire, provided that the integrity of the ceiling system can be maintained. However, significant lateral deflections up to 185 mm are predicted in a standard fire, which threatens the integrity of the ceiling. Under parametric fire conditions, a cooling phase suggests that there is negligible permanent deformation after a fire, due to the flexibility of the structure. Ultimately the results are used to make recommendations that: (a) steel end connections are designed to provide negligible moment restraint (b) slotted bolt holes are provided to allow free thermal expansion, and (c) the ceiling system is carefully detailed to accommodate the predicted lateral deflections, thereby safeguarding the integrity.

A two-step approach to solve the issue of dew condensation for displacement ventilation and chilled ceiling system

Abstract The displacement ventilation and chilled ceiling (DVCC) is a promising technique for the design of comfortable and energy saving ventilation and air conditioning system. However, dew condensation on the chilled ceiling is a main disadvantage for the application of DVCC system. In this paper, the variation of temperature and humidity in the room with DVCC system is numerically studied. A two-step approach is proposed to solve the issue of dew condensation. The independent operation time of displacement ventilation before running the chilled ceiling is discussed. The results will provide an insight for solving the issue of dew condensation on the chiller ceiling of DVCC system.