One of the factors that limit the cooling capacities and application potentials of radiant cooling panels is the condensation risk. The self-condensate-repellency tendency of superhydrophobic surface ...materials provides a possibility to mitigate the condensation risk. This paper studied the size ranges of condensate drops formed on a superhydrophobic aluminum sheet of the size 25 mm × 25 mm attached to a cooled ceiling panel in a climate chamber in the humidity range between 50% and 80% and at the temperature of 25 °C and air change rates from 0 ACH to 9 ACH. Using an optical magnifier, large drops up to the size 802.5 µm were observed in certain fixed positions in the large view area of 4.08 mm × 3.06 mm under different experimental conditions; whereas in a smaller focused view area of 0.96 mm × 0.72 mm the diameters of the largest drops were found to first increase over time and then reached around 80 µm with occasional size of 152 µm. All these were in contrast with the continuously growing drops simultaneously observed on the ordinary aluminum sheet, which reached 4 mm. The largest size of the droplets in the small focused area increased from 54.1 µm to 151.7 µm as humidity increases from 50% to 80%, but did not change much as the air change rate changed from 0 ACH to 9 ACH. This series of experiments confirm our hypothesis that condensate drop sizes can be limited within the un-perceivable range, namely below the sensory and visual thresholds, in typical indoor conditions because of the droplet jumping mechanism that occurs on the nano-engineered superhydrophobic surface, but it remains to be ascertained whether the large condensate drops formed at certain fixed points in the other parts of the tested nanostructured surface were associated with some defects in the nano-scale, and whether this can be eliminated on a larger area of practical application scale.
Diffuse Ceiling Ventilation (DCV) is a promising concept to address internal air quality and thermal comfort requirements in contemporary buildings. Sound-absorbing perforated ceiling panels are ...common in office rooms and can be used as air diffusers without modifications. The optimization of such systems is not a trivial procedure, and numerical simulation can represent an important tool to carry out this task. Today, most of the numerical studies on DCV are performed using porous medium models and focus on the general system performance rather than on the optimization of the diffuser design. In previous studies, a CFD model was used to optimize the size and distribution of the ceiling perforation. In the study presented in this paper, the results of simulations conducted on a full-scale three-dimensional domain and the performance comparison between a continuous and non-continuous perforation distribution are given. The results show that the non-continuous diffuser design does not disturb the internal comfort and does not introduce a negative effect in the system performance. The different configurations lead to a different air distribution in the room, but in both cases, the velocity magnitude is always well below values leading to draft discomfort.
The cooling capacity of a radiant ceiling panel (RCP) is highly limited in hot and humid climates as the panel surface temperature must be controlled higher than the air dew point to avoid ...condensation. Previous research suggested that condensation risks can be mitigated by using superhydrophobic surface materials, making ceiling panels applicable with the surface temperature below the air dew point. In this study, the enhanced cooling capacity of RCP due to latent heat transfer is estimated. Firstly, the condensation heat transfer of a superhydrophobic aluminum surface under natural convection in humid air with subcooling degrees between 3 °C and 12 °C was investigated by experiments. The data proved that the heat and mass transfer analogy method can be used to well predict the condensation heat transfer of the superhydrophobic surface with an error within 15%. Based on the finding, the heat and mass transfer analogy and traditional empirical methods were employed to predict the total heat flux of RCP with latent heat transfer. The results indicated an enhancement of 3% to 500% for the total heat flux compared with RCP with only sensible cooling, depending on the panel surface temperature, air temperature and humidity. This study draws a clear picture of how the cooling capacity of RCP can be enhanced via a latent heat transfer process, and this can be realized not necessarily with net moisture removal capacities with hydrophobic surfaces due to the droplet jumping phenomenon and the due re-evaporation process, showing a hidden potential of radiant cooling panels.
The use of radiant systems for cooling purposes in buildings is attracting considerable attention, particularly for Suspended Radiant Ceiling Panels (SRCPs). However, the arrangement of the panels on ...the ceiling and the influence on radiative heat transfer is rarely discussed in the literature. The objective of this paper is to provide a numerical study of the radiative heat transfer at room scale when the size and the number of SRCPs varies. It has been observed that the use of a single large panel would result in a low average temperature, which is desirable, but also in poor uniformity of the temperature field. Here, a genetic algorithm is proposed and tuned to determine the positions of multiple SRCPs that would improve uniformity. It is shown that much better uniformity can be obtained, with only a moderate increase in the average temperature, for 10 panels or more. The differences between the use of a single large panel and multiple panels is noteworthy when SRCPs cover from 10 to 70% of the ceiling area.
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•This study presents dynamic simulations of a full scale office building with 160 zones.•Fifteen energy performance cases for three climate zones of Helsinki, London and Bucharest ...were simulated.•Alternative heating and cooling solution using radiant floor panel and radiant ceiling panel were explored.•It is easier to minimize the space heating demand of a building then electricity.•Near optimal solutions for achieving nearly zero energy building based on this study are presented.
Most of the studies encompassing dynamic simulations of multi-storey buildings account only for a few selected zones, to simplify, decrease simulation run-time and to reduce the complexity of the ‘to be simulated’ model. This conventional method neglects the opportunity to see the interaction between different zones as it relates to whole building performance. This paper presents fifteen individual cases of dynamic simulations of a six-storey office building with 160 zones. The energy performance analysis was conducted for three climate zones including Helsinki in Finland, London in the United Kingdom and Bucharest in Romania. For each location, the following three cases were simulated: (i) building as usual simulated according to valid national building codes; (ii) Energy-efficient (EE) case with selected necessary parameters enhanced to reduce total delivered energy demand; and (iii) nZEB case representing partial enhancement of the EE case based on the parametric analysis. The results of nZEB indicate that for Helsinki, it is possible to reduce the space-heating load by 86%, electricity consumed by lighting, appliance, and HVAC by 32%. For London, the heating load is reduced by 95%, cooling load is slightly increased, and electricity demand is decreased by 33%. For Bucharest, 92% of energy in heating can be saved, cooling energy demand was reduced by 60% and electricity consumption by 34%. Based on the nZEB cases for each location, alternative heating and cooling choices of a radiant floor panel system and radiant ceiling panel system were explored. There are small differences in absolute consumption demand for heating, cooling, and electricity for three cases in each location. The specific energy/m2 for heating remained nearly the same in all systems for all three cases in each location. Alternative choices for heating and cooling by using Radiant Ceiling Panel (RCP) and Radiant Floor Panel (RFP) were investigated for all final nZEB cases. Marginal difference in heating energy required for space heating can be seen for London nZEB IHC and London nZEB RCP of 0.8kWh/m2/year and for Bucharest nZEB IHC and Bucharest nZEB RCP case of 1.3 kWh/m2/year. RFP has the availability of large surface area for heat exchange and can provide heating at a low temperature and cooling at high temperature, but requires supporting air based cooling during the humid season. For RCP, the limited temperature exchange surface may increase the airflow rate, but supplies it at a lower temperature for the same load.
Climate change has brought a compelling need for cooling living spaces to the attention of researchers as well as construction professionals. The problem of overheating enclosures is now exacerbated ...in traditionally affected areas and is also affecting countries that were previously less prone to the issue. In this paper, we address measurements of thermal comfort and cooling emission efficiency parameters for different devices: ceiling panels, underfloor cooling, fan-assisted radiators, and fan coil. These devices were tested in low and high cooling capacities of up to 40 W/m2 while also featuring heating dummies to imitate internal heat gains. Air temperatures were measured at different heights, allowing to evaluate the thermal stratification with high accuracy. Thermal comfort differences of the tested systems were quantified by measuring both air velocities and operative temperatures at points of occupancy. In summary, the best-performing cooling devices for the studied cooling applications were the ceiling panels and fan radiators, followed by underfloor cooling, with a limitation of stratification. Because of the strong jet, fan coil units did not achieve thermal comfort within the whole occupied zone. The results can be utilized in future studies for cooling emission efficiency and energy consumption analyses of the different cooling devices.
Mean radiant temperature (MRT) is one of the six primary factors that determine thermal comfort in a given thermal environment. In this study, the average radiant temperature was determined using a ...calculation method based on the surrounding surface temperatures and view factors. The present study specifically investigated the use of calculated radiant temperature, compared to measured radiant temperature, for predicting the mean vote (PMV) and percentage of dissatisfied (PPD) comfort parameters. The method was validated by the experimental measurements via the black sphere thermometer at five different reference points in a test room, including radiant panels on the ceiling and walls. By using global thermometer measurements, the proposed approach achieved a high degree of compatibility and an accuracy of 0.17 °C, which was the difference between calculated and measured values. The results demonstrated the reliability of the procedure using view factors and surrounding surface temperatures to calculate the radiant temperature in the designated test room; here, a straightforward method for evaluating the thermal conditions of an office room and determining the optimal location of an air temperature sensor in PMV-controlled radiant systems was also proposed. This study contributes to the increasing field of research on thermal comfort and offers knowledge that is beneficial for the design and optimization of indoor environments.
This paper analyses office cooling systems based on all air mixing ventilation systems alone or coupled with radiant ceiling panels. This last solution may be effectively applied to retrofit all air ...systems that are no longer able to maintain a suitable thermal comfort in the indoor environment, for example in offices with high thermal loads.
This study was performed by means of CFD simulations previously validated through an experimental campaign performed in a full scale test room, simulating a typical two-desk office equipped with an all air mixing ventilation system. The numerical studies were then extended to the coupled mixing ventilation and cold radiant ceiling panels.
In particular, attention was drawn on the evaluation of the main supply jet properties (throw and penetration length) and on the draft risk caused by the cold air drop into the occupied zone. The study shows that such a problem can be effectively reduced applying cold radiant ceiling panels.
Reverberation time (RT) is an important factor affecting the quality of indoor acoustics. Using sound-absorbing materials is one method for quickly and effectively controlling RT, and installation in ...the ceiling is a common location. Sound-absorbing ceilings come in many forms, with light steel joist ceilings commonly used in office spaces, classrooms, and discussion rooms. Light steel joist ceilings are often matched with sound-absorbing materials such as gypsum board, mineral fiberboard, rock wool, and coated glass wool, but such materials may have durability and exfoliation problems. Therefore, considering performance and health, in this research, we aimed to design an expanded metal mesh (EMM) structure specimen for sound-absorption material, namely folded expanded metal mesh (FEMM). The results show that the FEMM can significantly improve the sound-absorption performance of the expanded metal mesh. The Math output errorαw of single panel is 0.05–0.35, and the Math output errorαw of FEMM is 0.65–0.85. On the other hand, the sound-absorption performance of the full frequency band has been significantly improved. Furthermore, the field validation result shows that RT decreased from 1.05–0.56 s at 500 Hz, meanwhile, the sound pressure level (SPL) is still evenly distributed, and speech clarity (C50) is increased by 5.6–6.5.
This paper presents partial results of chemical analysis of concrete structures exposed to a long-term aggressive environment. The results characterize chloride load of the concrete elements. As the ...samples for analysis, fragments of the existing concrete ceiling panels and beams stored in a skylight of one of the monitored structures for a long time were used.
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