Increased potential for energy savings through increasing cooling capacity further in diffuse ceiling ventilation
Using diffusive ceiling ventilation lower inlet temperatures can be used compared to traditional ventilation principles. The system is able to cope with larger cooling needs e.g. in combination with use of outdoor air for natural cooling. Within the project the potential for energy savings through increasing the cooling capacity further will be analyzed. The dependence of the cooling capacity on the location of heat loads in the room and the distribution of diffusive supply areas in the ceiling will be analyzed.
Diffuse ceiling ventilation makes it possible to use lower temperature of the supply air compared to traditional ventilation principles, e.g. mixing ventilation. Also, use of low supply temperature and large air flow is possible without use of mechanical cooling machines. Thus, diffuse ceiling ventilation is able to cope with large cooling needs and it is obvious to combine the system with the use of outdoor air for natural cooling.
The objective of the project is to analyze the potential for energy saving through increasing the cooling capacity further using diffuse ceiling ventilation. Within the project the dependence of the cooling capacity on the location of heat loads in the room and the distribution of diffusive supply areas in the ceiling will be analyzed.
The project will comprise a combination of CFD-calculations and laboratory investigations. The CFD-calculations will demonstrate the limits for the temperature difference between the inlet temperature and the indoor temperature (exhaust temperature) at a given air flow rate, depending on the location of the heat load in the room and the distribution of the diffusive inlet areas in the ceiling, providing draught in the occupied zone will not occur.
Selected scenarios from the CFD-calculations will be verified through investigations in a test room in the laboratory. The CFD-calculations as well as the laboratory investigations will take into account different seasons, such as cold winters and warm summers. The results of the CFD-calculations and the laboratory investigations will provide a basis for analyzing the increased cooling capacity under different conditions. The results of the project will be disseminated as a conference paper, a scientific article and a popular article.
This research evaluates experimentally the cooling capacity of the diffuse ceiling ventilation system and its dependency to the relative location of heat sources in the room and the diffuse panel area in the ceiling.
Several scenarios were tested in a test room with the diffuse ceiling and the dimension of 4.2×3.6×2.5 m (L×W×H). The different scenarios were compared through a design chart showing the limits on the supply airflow rate and the temperature difference between supply and exhaust air in order to have either a constant air velocity in the room or a constant heat load removed from the room.
Two different diffuse panel ratios in the ceiling, i.e. 100% and 2.4% diffuse ceiling, were considered. In the case of 100% diffuse ceiling, the cooling capacity was higher when the heat sources were distributed evenly in the room. In the case of 2.4% diffuse ceiling, the cooling capacity reduced when the heat sources were exactly placed below the inlet diffuse ceiling. Comparing the systems with the same heat sources distribution in the two different diffuse panel ratios revealed that a higher cooling capacity is possible for a smaller diffuse panel ratio. The system with 2.4% diffuse ceiling had a higher cooling capacity compared to the 100% diffuse ceiling in the rather low supply airflow rate of 40 l/s. However, the cooling capacity reduced rapidly in the small ratio of diffuse panel with the increase of the supply airflow.
In fact, the system was rather a mixing ventilation system than a diffuse ceiling ventilation system in the small ratio of perforated to non-perforated panels. In addition, several experiments were run to see the influence of different start-up operations, i.e. whether the heat sources or the ventilation starts operation first. The results showed an insignificant effect of different start-up operations on the cooling capacity.
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Participants
| Partner | Subsidy | Auto financing |
|---|---|---|
| TROLDTEKT A/S |
