Ceiling Surface Temperature Research Articles

Experimental Investigation of Wall Confluent Jets on Transparent Large-Space Building Envelopes: Part 1—Application in Heating Greenhouses

Insulating building envelopes is crucial for maintaining indoor thermal comfort, particularly in large-space enclosures like greenhouses having transparent envelopes. Transparent envelopes allow natural light but challenge temperature regulation due to their low thermal mass and high U-values, which enable significant heat transfer between indoor and outdoor environments. This field study aims to experimentally investigate whether warm wall confluent jets (WCJs) can maintain the required indoor climate conditions in a greenhouse exposed to dynamic meteorological conditions in winter. It analyzed the impact of the airflow rate, number of nozzle rows, and room air temperature setpoint on WCJ heating performance on the ceiling, external wall, and room air. Measurements were performed with thermocouples and constant current anemometers, and the response surface methodology evaluated the effect of design variables on WCJ flow, thermal behavior, and the indoor environment. The results show that WCJs provided recommended air velocities and temperatures indoors, with the airflow rate having the strongest effect on flow and thermal behavior, while the number of nozzle rows had a moderate effect. This study developed response surface models related to room air temperature, ceiling surface temperature, external wall temperature, and supply air temperature. Supply temperatures between 27 °C and 40 °C suggest using low-exergy heat sources, like industrial waste heat, to sustain greenhouse operations during winter.

Allowable surface temperature of ceiling heating based on radiant temperature asymmetry

Radiant temperature asymmetry as one of the criteria for local thermal discomfort has an influence on the practical design of the heating system, as people are most sensitive to the radiant heating of the top of the head. The paper presents the determination of the allowable surface temperature of the heated ceiling based on the theoretical calculation using the angle factors and taking into account the allowable the radiant temperature asymmetry according to the standard values of 5 and 7 K. In practice, the radiation temperature asymmetry is determined by measuring two radiant temperatures. In this paper, the measurement of radiant temperature asymmetry is measured in an experimental room with a heated ceiling and the results are compared with the theoretical calculation procedure. The paper points out the differences between the measured and calculated values of the radiant temperature asymmetry. Based on the analyses, the allowable ceiling temperatures for radiant heating have been determined for different room geometries so that the radiant temperature asymmetry for thermal comfort categories A, B is actually observed. A new correlation has been established to determine the allowable surface temperature of the radiant ceiling as a function of the angle factor between the small plane element and the ceiling. For practical use, the correlation has been adjusted for typical geometric cases without the need for calculation of angle factors. Maximum ceiling surface temperatures are graphically displayed without causing thermal discomfort. Conversely, in large rooms with a heated ceiling, the ceiling surface temperature is severely limited, precisely because of the potential for thermal discomfort due to radiant temperature asymmetry.

Study of Roof and Ceiling Surface Temperatures in Coastal Area (Case Study: Pasar Bengkulu Village)

Abstract The majority of residential roofs in Pasar Bengkulu Village are constructed using corrugated iron and galvalum metal. These coastal areas often grapple with high levels of solar heat radiation. Both corrugated zinc and galvalum roofing materials are known for their high heat conductivity and excellent heat-reflecting capabilities. To combat this, solar reflectance paint is often used to reflect solar radiation heat, thereby reducing heat absorption. This research is a qualitative research with a focus on the description and analysis of measured data which aims to compare the surface temperature of the roof and ceiling before and after being coated with reflective solar paint. This research was conducted to determine the difference in roof and ceiling surface temperatures before and after the application of solar reflective paint. The results of the roof surface temperature measurements revealed that galvalum metal roofs exhibited the most significant reduction in roof surface temperature, with a decrease of 9.1°C.

Investigation on the burning behaviors of the combustible ceiling with the impingement of an incipient fire source

This paper presents experimental and theoretical research on ceiling jet, burn-through, and flame spread behaviors of the combustible ceiling with the impingement of an incipient fire source. Medium-density fiberboard was utilized as the combustible ceiling in experiments, and the ceiling height above the fire source was varied. The flame radial length (rf), ceiling surface temperature, flame shape and spread rate after burn-through, and radiative heat flux were measured. Results showed that rf beneath the combustible ceiling was significantly longer than that of the non-combustible ceiling. Theoretical analysis was conducted for rf based on energy distribution, and an expression of rf beneath combustible ceiling was proposed. The burn-through behavior of the combustible ceiling was explored by combining the ceiling temperature, small-sized experiment and Fourier law. The advancement of char front along the ceiling thickness was calculated, which was the key point during burn-through. Upper surface flame spread in a circular shape after burn-through, and an expression of spread rate was obtained. A three-dimensional radiation model was adopted to calculate the radiative heat flux received by the unburned ceiling surface during the dynamic flame spread process, the calculated results agreed well with the experimental data.

The Application of UAVs in the Evaluation of Thermal Comfort Levels in Buildings Equipped with Internal Greenhouses

A greenhouse is used to improve thermal comfort (TC) levels for its occupants in winter conditions using solar radiation, which involves low energy consumption. The aim of this research is the application of unmanned aerial vehicles (UAVs) in the evaluation of thermal comfort levels in buildings equipped with internal greenhouses. The new building design is developed numerically, and a building thermal simulator (BTS) numerical model calculates the indoor environmental variables. A new alternative and expeditious method to measure occupants’ comfort levels using UAV technology is applied using a UAV dynamic simulator (UAV DS). The evolution of the measured variables used for evaluating the predicted mean vote (PMV) is compared using the two numerical methodologies: BTS and UAV DS. In the second one, the mean radiant temperature (MRT) measuring methodology, the floor temperature, the lateral walls’ temperatures, the ceiling temperatures, and the air temperature are applied. In the method presented in this paper, a new building design is developed numerically, which includes a central greenhouse equipped with a semispherical dome, four auditoriums distributed around the central greenhouse, occupant distribution, and a ventilation methodology. The building geometry, the solar radiation on transparent surfaces, the TC, and the UAV mission methods are presented. The results show that, in general, the central greenhouse and the ventilation methodologies provide acceptable TC levels. The UAV monitoring mission, which includes two vehicles, provides good environmental variable replication, particularly when the environmental variables present greater variations. In the auditorium and greenhouse, the ceiling and lateral surface temperatures, respectively, can be used as an MRT approximation. The BTS numerical model is also important for developing buildings using renewable energy sources to improve the TC levels.

Experimental Study of Indoor Air Distribution and Thermal Environment in a Ceiling Cooling Room with Mixing Ventilation, Underfloor Air Distribution and Stratum Ventilation

A ceiling cooling system integrated with a mechanical ventilation system has been widely used in modern buildings with large sensible cooling loads due to the high thermal comfort level and large energy efficiency. However, there is a lack of systematic research on the influence factors such as ceiling surface temperature and cooling load on the indoor air distribution and thermal environment, and the impact of ventilation system type in the ceiling cooling room is still unclear. Therefore, this paper presented an experimental study of indoor air distribution and thermal environment in a ceiling cooling (CC) room with mixing ventilation (MV), underfloor air distribution (UFAD) and stratum ventilation (SV); the ceiling surface temperature was 17 °C–26 °C and the internal or external cooling load was 41.5 W/m2–69.5 W/m2. The results showed that the vertical air temperature difference and contaminant removal effectiveness were 0.2 °C–0.4 °C and 0.53–0.85 with CC + MV, 0 °C–1.2 °C and 0.68–1.25 with CC + UFAD and 0.3 °C–0.9 °C and 0.50–0.83 with CC + SV, and the corresponding heat removal effectiveness and air diffusion performance index were 0.96–1.11 and 96–100%, 0.9–1.5 and 57–100% and 1.11–1.34 and 71–100%, respectively. Moreover, the difference between mean radiant temperature and air temperature and the predicted mean vote of thermal sensation were from 0 °C to 0.9 °C and between 0 and 0.26 with CC + MV, from −0.1 °C to 2.2 °C and between −0.1 and 0.42 with CC + UFAD and from −0.1 °C to 0.9 °C and between −0.2 and 0.13 with CC + SV. Hence, the ventilation system type clearly affected the indoor air distribution and thermal environment in the ceiling cooling room, and the experimental results would be beneficial for the design and control of a ceiling cooling system combined with a mechanical ventilation system in practice.

Heating Ceiling System Efficiency in Different Climate Zones

Abstract There are many benefits of building construction with prefabricated thermo active ceilings technology, and the most highlighted are: short lead time, ease of installation, low price, lack of taking up space in a room and additionally the possibility of working in heating and/or cooling mode. An analysis was carried out to illustrate the factors that influence the thermal output of a ceiling heating system in residential buildings located in 5 climate zones in Poland and 2 in Ukraine. The thermal loads were determined for the entire building, designed in accordance with the regulations in force in each country, for the flats and particular rooms (considering the heat exchange between the flats according to PN-EN 12831:2006). An average heating medium temperature of 34°C was assumed. The results were compared with the achievable heating capacity of the ceiling system, which results from the difference between the heating medium temperature and the indoor room temperature. It was investigated that the system achieves the calculated output in all climate zones in Poland, while it will not be sufficient in Ukraine. This is due to both less stringent building thermal protection regulations and different indoor design temperature values, resulting in a higher average temperature in the flat. When analysed on a room-by-room basis, it became apparent that in all considered locations there were rooms for which the heating capacity was insufficient. In the climate zones I to IV in Poland, the problem concerns only bathrooms, where in this case quite often the surface heating can be combined with a supplementary electric radiator. In the V climate zone in Poland and both in Ukraine, the solution to the power shortage under design conditions may be: building construction according to a higher energy standard, increasing the supply temperature (with the limitation of maximum ceiling surface temperature to 35°C for living spaces) or using additional heating elements not only in bathrooms. A novel part of the article discusses calculated power shortages in relation to climate change and the external design temperatures suggested by sources other than the standard.

Sensitivity analysis of indoor air distribution performances in an office room with ceiling cooling and mechanical ventilation

A hybrid system with a ceiling cooling (CC) system and a mechanical ventilation system has been extensively applied in modern office buildings with large sensible cooling loads. Both the chilled ceiling and supply air may greatly influence indoor air distribution in the office room. Therefore in this paper, indoor air distribution performances in a ceiling cooling room with underfloor air distribution (UFAD) or mixing ventilation (MV) were sensitively analyzed by numerical simulation. Indoor air distribution performances, which were evaluated by the heat removal effectiveness, contamination removal effectiveness and air diffusion performance index, were quantitatively analyzed by using the orthogonal experiment method. The results showed that when the supply air temperature was 18 °C-24 °C for CC + UFAD and 16 °C-21 °C for CC + MV, the heat removal effectiveness changed by 0.01 with 1 °C increment of supply air temperature or ceiling surface temperature, and the contamination removal effectiveness increased by 0.001-0.002 with 1 W/m2 increment of external sensible cooling load. Moreover, the air diffusion performance index increased by 0.6%-1.1% with 1 °C increment of supply air temperature, and it decreased by 0.02% with 1 W/m2 increment of internal sensible cooling load. Finally, formulas of heat removal effectiveness, contamination removal effectiveness and air diffusion performance index for CC + UFAD and CC + MV were obtained by fitting, and they may provide guidance for the optimal design and control of a hybrid system with a ceiling cooling system and a mechanical ventilation system.

Predicting the temperature distribution of a non-enclosed atrium and adjacent zones based on the Block model

The thermal conditions of a non-enclosed atrium and the adjacent zones are significantly related. We propose an extended Block model to predict their vertical temperature distribution by incorporating mass and heat transfer processes (horizontal convection and descending flow deflection). Regarding the air flowing horizontally from the adjacent zones into the atrium and deflecting to other adjacent zones during descent, the deflection modulus Dn was derived to evaluate the deflection states. Therefore, a mathematical model for predicting the indoor temperature was built by coupling the typical airflow patterns in a non-enclosed atrium with the Block model. The accuracy of the predicted temperatures was verified using the field measurement results obtained in a shopping mall. Using the proposed model, the effects of indoor parameters (including the height of the opening connecting the atrium and the adjacent zones and the heat source conditions indicated by the atrium's ceiling and floor surface temperatures) on the temperature distribution and airflow patterns were analysed. The temperature inside the atrium, especially the temperature gradient in the upper spaces, is mainly affected by the heat transferred from the ceiling but is weakly affected by the temperature level near the floor. The more heat is transferred from the ceiling relative to the floor, the earlier the airflow's deflection stops during descent. Shortening the opening height reduces the adjacent zones' vertical temperature gradient without affecting the deflection states. The method and conclusion of this study provide insights for predicting and optimising the thermal environment of similar spaces.

Impact of ventilation system type on indoor thermal environment and human thermal comfort in a ceiling cooling room

A ceiling cooling (CC) system integrated with a mechanical ventilation system is an advanced HVAC system for the modern office building with glass curtain wall. In this paper, considering the influence of heat transfer of external envelope, the indoor thermal environment and human thermal comfort were objectively measured and subjectively evaluated in a CC room with mixing ventilation (MV) or underfloor air distribution (UFAD). Indoor physical parameters and human skin temperatures were measured as the chilled ceiling surface temperature and supply air temperature were 17.1-17.6? and 22.2-22.6?. Simultaneously, 16 subjects (8 males and 8 females) were selected to subjectively evaluate the thermal environment. The results showed that the difference between mean radiant temperature and air temperature in the occupied zone was 0.8? with CC + MV and 1.2? with CC +UFAD, and the indoor air velocity was 0.17 m/s with CC + MV and 0.13 m/s with CC + UFAD. In addition, the calculated and measured thermal sensation votes with CC + MV were all slightly less than those with CC + UFAD. Therefore, ventilation system type had a slight impact on the indoor thermal envi?ronment and human thermal comfort in the CC room.

Comparison of Indoor Air Distribution in a Ceiling Cooling Room with Different Mechanical Ventilation Systems

This paper presents an experimental study concerning the influence of ventilation system type on indoor air distribution in a ceiling cooling (CC) room with mixing ventilation (MV), underfloor air distribution (UFAD) and stratum ventilation (SV) when the internal or external cooling load was increased from 41.5 W/m2to 69.5 W/m2. The distributions of indoor air temperature, air velocity and contaminant concentration were measured and evaluated by the vertical air temperature difference, turbulence intensity and contaminant removal effectiveness, respectively. The results show that when the ceiling surface temperature increased from 17.0°C to 26.0°C, the vertical air temperature differences, turbulence intensities and contaminant removal effectiveness were 0.2°C-0.4°C, 27%-34% and 0.53-0.85 with CC+MV, 0.2°C-1.2°C, 27%-43% and 0.68-1.25 with CC+UFAD and 0.3°C-0.9°C, 24%-40% and 0.5-0.83 with CC+SV. The CC+MV had the most uniform distributions of indoor air temperature and velocity, whereas the CC+UFAD had the most non-uniform distribution of indoor contaminant concentration.

Generalized Additive Modeling of Building Inertia Thermal Energy Storage for Integration Into Smart Grid Control

The structural mass of a building provides inherent thermal storage capability. Through sector coupling, the building mass can provide additional flexibility to the electric power system, using, for instance, combined heat and power plants or power-to-heat. In this work, a mathematical model of building inertia thermal energy storage (BITES) for integration into optimized smart grid control is introduced. It is shown how necessary model parameters can be obtained using generalized additive modeling (GAM) based on measurable building data. For this purpose, it is demonstrated that the ceiling surface temperature can serve as a proxy for the current state of energy. This allows for real-world implementation using only temperature sensors as additionally required hardware. Compared with linear modeling, GAM enable improved modeling of the nonlinear characteristics and interactions of external factors influencing the storage operation. Two case studies demonstrate the potential of using building storage as part of a virtual power plant (VPP) for optimized smart grid control. In the first case study, BITES is compared with conventionally used hot water tanks, revealing economic benefits for both the VPP and building operator. The second case study investigates the potential for savings in CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emission and grid connection capacity. It shows similar benefits when using BITES compared to using battery storage, without the need for hardware investment. Given the ubiquity of buildings and the recent advances in building control systems, BITES offers great potential as an additional source of flexibility to the low-carbon energy systems of the future.

Influence of sensible cooling load on indoor air distribution in an office room with ceiling cooling and mixing ventilation

A mixing ventilation system integrated with a ceiling cooling system is a potential advanced heating, ventilation and air conditioning system for modern office buildings with a high sensible cooling load. This paper presents an evaluation of the effect of sensible cooling load on the indoor air distribution in a typical office room with mixing ventilation and ceiling cooling. The vertical distributions of indoor air temperature, air velocity and contaminant (CO2) concentration were evaluated by the vertical air temperature difference, turbulence intensity and contaminant removal effectiveness. The results showed that when the chilled ceiling surface temperature was increased from 15.0°C to 23.0°C and supply air temperature was decreased from 22.0°C to 19.0°C, the average vertical air temperature difference, turbulence intensity and contaminant removal effectiveness were 0.2°C–0.3°C, 27%–32% and 0.53–0.81 as both internal and external sensible cooling loads were 41.5 W/m2. Moreover, these evaluation indices varied slightly as the external sensible cooling load was increased from 41.5 W/m2 to 69.5 W/m2, whereas they varied greatly as the internal sensible cooling load was increased from 41.5 W/m2 to 69.5 W/m2. Hence, the external sensible cooling load could slightly affect the indoor air distribution, whereas the internal sensible cooling load could clearly affect the indoor air distribution in an office room with mixing ventilation and ceiling cooling.

Performance of capillary ceiling cooling panel on ceiling surface temperature and indoor thermal environment

A new experimental methodology is presented to show the effect of water supply temperature, mass flow rate and thermal load distribution on the radiant ceiling capacity and thermal comfort conditions. Computerized fluid dynamics simulated vertical temperatures and velocities profiles were validated by a comparison with experimental results and the difference was within 10%. Uniform surface temperature distribution was achieved in a 45.6 m3 test room installed with capillary ceiling radiant cooling panels by an increase in water temperature and air supply velocity. When the ventilation system was turned off, the mean ceiling surface temperature rose from 16.9 ± 0.4°C to 21.5 ± 0.3°C with a rise in the inlet water temperature to 20.1°C. The temperature difference between the head and ankle of an occupant was 2.0°C, which complies with the Chinese standard, GB/T 18049-2017. At a height of 1–1.5 m, the maximum temperature fluctuation was 2°C in the horizontal direction. When the ventilation system was turned on, with the air supply temperature and velocity at 19.8°C and 1.11 m s−1, the ceiling surface temperature was increased by 0.5°C. The indoor air temperature has a positive correlation with the air supply temperature and internal heat load but a negative correlation with air supply velocity.

Green Roofs as Effective Tools for Improving the Indoor Comfort Levels of Buildings—An Application to a Case Study in Sicily

In the line of pursuing better energy efficiency in human activities that would result in a more sustainable utilization of resources, the building sector plays a relevant role, being responsible for almost 40% of both energy consumption and the release of pollutant substances in the atmosphere. For this purpose, techniques aimed at improving the energy performances of buildings’ envelopes are of paramount importance. Among them, green roofs are becoming increasingly popular due to their capability of reducing the (electric) energy needs for (summer) climatization of buildings, hence also positively affecting the indoor comfort levels for the occupants. Clearly, reliable tools for the modelling of these envelope components are needed, requiring the availability of suitable field data. Starting with the results of a case study designed to estimate how the adoption of green roofs on a Sicilian building could positively affect its energy performance, this paper shows the impact of this technology on indoor comfort and energy consumption, as well as on the reduction of direct and indirect CO2 emissions related to the climatization of the building. Specifically, the ceiling surface temperatures of some rooms located underneath six different types of green roofs were monitored. Subsequently, the obtained data were used as input for one of the most widely used simulation models, i.e., EnergyPlus, to evaluate the indoor comfort levels and the achievable energy demand savings of the building involved. From these field analyses, green roofs were shown to contribute to the mitigation of the indoor air temperatures, thus producing an improvement of the comfort conditions, especially in summer conditions, despite some worsening during transition periods seeming to arise.

Impact of chilled ceiling on indoor air distribution in a room with mixing ventilation

A mixing ventilation (MV) system integrated with a chilled ceiling (CC) cooling system will be a potential advanced heating, ventilation and air conditioning (HVAC) system in the modern buildings. This paper presented an experimental study concerning the effect of CC on the indoor air distribution with MV when the internal and external sensible cooling loads changed. The vertical distributions of indoor air temperature, air velocity and contaminant (CO2) concentration were evaluated by the vertical air temperature difference, turbulence intensity and contaminant removal effectiveness, respectively. The results showed that when chilled ceiling surface temperature ranged from 17.0 °C to 26.0 °C, the average vertical air temperature difference, turbulence intensity and contaminant removal effectiveness were 0.2 °C–0.4 °C, 30%–36% and 0.6–0.84 when both internal and external sensible cooling loads were 41.5 W/m2. Moreover, the ranges of these evaluation indices varied slightly when the internal or external sensible cooling load increased from 41.5 W/m2 to 69.5 W/m2. Hence, the chilled ceiling had a slight impact on the indoor air distribution in a room with mixing ventilation. It is interestingly found that the small vertical air temperature difference coincided with the large turbulence intensity and contaminant removal effectiveness with different internal or external cooling loads.

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.

Dynamic variation of surface temperatures on the radiant ceiling cooling panel based on the different supply water temperature adjustments

Radiant ceiling cooling panels has been easily integrated with air system to reduce the building energy consumption, yet their surface is prone to condensation, restricting the application of such systems in hot and humid climate. In order to prevent surface condensation of the radiant ceiling panels, the dynamic temperature changes of radiant ceiling panel surface must be fully understood. In this paper, experiments are used to investigate radiant ceiling panel surface temperature changes. Experimental results are used to perform numerical simulations and a SAS (Statistical Analysis System) program via linear regression method, in order to study the effect of supply water temperature adjustments on the dynamic temperature changes of radiant ceiling panel surface. Results show that radiant ceiling panel surface temperatures change exponentially with water supply temperature changes when there is a danger of condensation on the radiant panel surface. When the water supply temperature rises, the surface temperature of the radiant ceiling panel increases, effectively preventing surface condensation occurrence and the variation of the supply water temperature has the greatest influence on the surface temperature of the radiant ceiling panel. When the supply water temperature is lowered, the indoor temperature has the greatest influence on the surface temperature of the radiant ceiling panel.

Impact of chilled ceiling in a high sensible cooling load room with underfloor air distribution

The use of an underfloor air distribution (UFAD) system integrated with a chilled ceiling (CC) cooling system can provide a potentially advanced heating, ventilation, and air conditioning (HVAC) system with high sensible cooling loads in modern office buildings. In this paper, an experimental study of the impact of CC in a room with a high sensible cooling load with UFAD was performed when the chilled ceiling surface temperature increased from 17.0 to 26.0 °C. The vertical distributions of indoor air temperature, air velocity, and pollutant (CO2) concentration were measured and evaluated by the vertical air temperature difference (VATD), turbulence intensity (TI), and contaminant removal effectiveness (CRE), respectively. The results showed that the average VATD, TI, and CRE were 0.1–0.9 °C, 4–40%, and 0.85–1.19, respectively, when the internal and external sensible cooling loads equal 41.5W/m2. These evaluation indices varied clearly when the internal sensible cooling load increased from 41.5 to 69.5W/m2, whereas they were almost the same when the external sensible cooling load increased from 41.5 to 69.5W/m2. The minimum CRE and air diffusion performance index (ADPI) coincided with the maximum heat removal effectiveness (HRE) under a constant cooling load condition. The results suggest that it is better to balance the energy consumption as well as indoor air quality and thermal comfort in a room with UFAD + CC.

Indoor air distribution in a room with underfloor air distribution and chilled ceiling: Effect of ceiling surface temperature and supply air velocity

An underfloor air distribution (UFAD) system integrated with a chilled ceiling (CC) cooling system may be a potential advanced heating, ventilation and air conditioning system in modern non-residential buildings with high sensible cooling loads. This article presents an experimental study concerning the effect of ceiling surface temperature and supply air velocity on the indoor air distribution in a room with UFAD as the internal and external sensible cooling loads change. The vertical distributions of indoor air temperature, air velocity and contaminant (CO2) concentration were evaluated by vertical air temperature difference (VATD), turbulence intensity (TI) and contaminant removal effectiveness (CRE), respectively. The results showed that the average VATD, TI and CRE levels were 0.5°C–1.0°C, 31%–41% and 0.85–1.06 when both internal and external sensible cooling loads were 41.5 W/m2. These evaluation indices varied clearly when the external sensible cooling load increased from 41.5 W/m2 to 69.5 W/m2, whereas they remained almost the same when the internal sensible cooling load increased from 41.5 W/m2 to 69.5 W/m2. The maximum TI coincided with the minimum CRE under the condition of a constant sensible cooling load. Moreover, an air diffusion performance index clearly reduced with an increase in the heat removal effectiveness. It is recommended that it is important to balance the indoor air quality and energy consumption in a room with UFAD + CC.