Cooled Ceiling Research Articles

Thermal Comfort Analysis of Personalized Conditioning System and Performance Assessment with Different Radiant Cooling Systems

The radiant systems consume less energy and provide better thermal comfort as compared to the conventional system, but the main drawback of radiant technology is inability to cater the latent load and condensation. This problem has engaged researchers to push their emphasis on Personalized Conditioning System (PCS). It forms a micro-climate region near the occupant. This study is aimed at PCS combined with a radiant conditioning system, which evaluates the performance of the PCS and compares it with different radiant cooling systems. A radiant cubicle was used to investigate the performance of the PCS for both heating & cooling modes. For heating mode, the Standard Effective Temperature (SET) was calculated with the help of thermal comfort surveys which were in a range of 23.4°C to 27.3°C. For cooling mode, four different cases compared the performance of the system which are: Conventional Air Conditioning System (CACS), Radiant Cooled Ceiling System (RCCS), Personalized Radiant Conditioning System (PRCS), and both PRCS-RCCS coupled. It was observed that PRCS alone reaches the thermal comfort criteria with low energy consumption. The energy-saving of RCCS-PRCS was achieved 38% when compared with CACS. It can be concluded that PRCS is a new step in the field of thermal comfort.

Comparative Study of Impact of Radiant Cooling Ceiling and Convective Air Conditioning on Wellness, Physiology and Productivity of Office Workers

Comparative Study of Impact of Radiant Cooling Ceiling and Convective Air Conditioning on Wellness, Physiology and Productivity of Office Workers

Simulation Research on the Thermal Performance of the Cooling Ceiling Embedded with Phase Change Material for Energy Storage

A radiant cooling ceiling which is embedded with capillary pipes and phase change material to store and supply cool was put forward. The mathematical model of such cooling ceiling which runs intermittently was set up to analyze its thermal performance. The influence of phase change material thermal storage performances on the average heat flux and energy storage ratio of the cooling ceiling was analyzed. The main factors affecting the thermal performance of the ceiling was obtained by sensitivity analysis. The cooling storage performance differences between the ceiling embedded with phase change material and the concrete ceiling were comparatively analyzed. The research results show that the energy storage ratio of the phase change energy storage ceiling is higher than that of the concrete ceiling.

Numerical Prediction of Thermal Comfort and Condensation Risk in a Ventilated Office, Equipped with a Cooling Ceiling

In the current context of more and more energy efficient buildings, performant HVAC systems are required. The solution based on radiant cooling ceiling systems has proven successful in terms of high energy efficiency and good levels of thermal comfort. Nevertheless, there is an important issue concerning the cooling ceilings: the risk of condensation. As a result, the aim of this study is to investigate the thermal comfort and condensation risk for buildings with ventilation systems and cooling ceilings. The approach is based on CFD (Computational Fluid Dynamics) technique, introducing special methodologies in order to deal with convection and diffusion phenomena for water vapor, required for comprehensive thermal comfort analyzes and condensation mechanisms. The numerical model is applied in the case of a small office, taking into account a radiant cooling ceiling over the entire ceiling surface and two configurations of ventilation systems: mixing ventilation and displacement ventilation. Several simulations have been completed for different conditions concerning the air flow rates of the ventilation systems and temperatures of the cooling ceiling. It has been concluded that mixing ventilation has superior behavior, both in terms of thermal comfort and condensation risk, when warm and moist air is supplied in the room. On the other hand, the results show that when untreated air is supplied by the ventilation system (no matter its configuration, mixing or displacement), thermal comfort in the office cannot be properly assured only by radiant cooling ceiling systems.

Performance Evaluation of Displacement Ventilation System Combined with a Novel Evaporative Cooled Ceiling for a Typical Office in the City of Beirut

The study investigates by modeling the performance of displacement ventilation (DV) aided with a Novel Evaporative Cooled Ceiling, Maisotsenko cycle (M-cycle). The proposed system will increase the load removal of the DV system beyond the 40W/m2 limit with no additional energy consumption. Predictive mathematical models of the conditioned space and the evaporative cooled ceiling will be developed to study the energy performance of the suggested combined system for typical offices of Beirut. The study identifies different values of supply air relative humidity at a certain supply flow rate and temperature while meeting space load, indoor air quality, and thermal comfort. The proposed system resulted in cooling load removal capacity enhancements of 18.65%, 44.3% and 72.25% at supply air relative humidity of 90%, 50% and 10 ̊C respectively. The results indicated a better performance at lower supply air relative humidity.

Research on Raising Load Potentials Using MPCM Slurry Storage

Evaporative cooling is able to generate the cooling medium at a temperature approaching to the ambient wet bulb temperature. In this paper, a low-energy air-conditioning strategy is proposed, which is a combination of cooled ceiling (CC),microencapsulated phase change material (MPCM) slurry storage and evaporative cooling technologies. The assessment of evaporative cooling availability and utilization is done for five representative climatic cities, including Hong Kong, Shanghai, Beijing, Lanzhou and Urumqi in China, and the energy saving potential of the proposed air-conditioning system is analyzed by using a well validated building simulation code. The results indicate that the new system offers energy saving potential up to 80% under northwestern Chinese climate and up to 10% under southeastern Chinese climate. The optimal design method of the slurry storage tank is also proposed based on the slurry cooling storage behaviors and cooling demand variations of the ceiling panels.

The Indoor Air Quality and Thermal Comfort Experimental Research on the Combined Cooling Ceiling and Displacement Ventilation System

In this energy saving and environment protection society, as a new kind of air conditioning system, the combined cooling ceiling (CC) and displacement ventilation (DV) system has been attracting more and more attention both at home and abroad. This paper has done experiments with different supply air temperature, various supply air velocity and changeable temperature of supply water by simulating to cool a small office in summer. Based on similarity theories, some suggestions are given for the numerical area of cooling parameters under some laboratory conditions. According to PMV, it is also presented in general guidance for indoor air quality and thermal comfort with CC/DV system.

Raising evaporative cooling potentials using combined cooled ceiling and MPCM slurry storage

Evaporative cooling is able to generate the cooling medium at a temperature approaching to the ambient wet bulb temperature. In this paper, a low-energy air-conditioning strategy is proposed, which is a combination of cooled ceiling (CC), microencapsulated phase change material (MPCM) slurry storage and evaporative cooling technologies. The assessment of evaporative cooling availability and utilization is done for five representative climatic cities, including Hong Kong, Shanghai, Beijing, Lanzhou and Urumqi in China, and the energy saving potential of the proposed air-conditioning system is analyzed by using a well validated building simulation code. The results indicate that the new system offers energy saving potential up to 80% under northwestern Chinese climate and up to 10% under southeastern Chinese climate. The optimal design method of the slurry storage tank is also proposed based on the slurry cooling storage behaviors and cooling demand variations of the ceiling panels.

New Convection Correlations for Cooled Ceiling Panels in Room with Mixed and Stratified Airflow

Models for buildings' surface convective boundary conditions are important components of building design and simulation programs. This is especially true for cooled ceiling (CC) panels, which extract major cooling loads from rooms. This paper introduces new convection correlations for rooms with CC panels, developed from laboratory measurements conducted in a full-scale experimental facility. The new convection correlations were developed for CC panels used with or without a ventilation system. When the ventilation system was used, the air was supplied through a high aspiration diffuser. High aspiration diffusers, recommended for use with CC systems, create a specific airflow pattern characterized by narrow and directional jets with a large entrainment of surrounding air. To account for the forced airflow and local buoyancy effects, new convection correlations for CC surfaces were developed as functions of temperature difference and normalized volume flow rate, i.e., the number of air changes per hour (ACH) in the room. Results show that the high aspiration diffuser, even though installed at the ceiling, produces enough air motion in the vicinity of the floor and vertical wall surfaces to affect the convective heat transfer at these surfaces as well. In fact, the effect of forced convection due to the presence of a high aspiration diffuser increases the total convection coefficient at CC surfaces by 4% to 17%.