engineers at zibell willner & partners (zwp) were able to substantially improve the ventilation of an exhibition pavilion in order to ensure comfort during summer months without having to provide air conditioning. they used flovent software from flomerics inc. to model the flow of air through the pavilion, and modified the model to solve problems that the simulation identified in the original design.

the pavilion, part of a much larger project, has an arched roof whose height rises from 3.7 meters to 7 meters. the fa�ade is glass from floor to ceiling. before finalizing the design of the building, zwp engineers wanted to investigate the capabilities and limits of natural ventilation under both winter and summer conditions. they were particularly concerned about thermal comfort parameters such as air temperature, radiant temperature and air speed in the occupied areas of the building.

the traditional approach to address these concerns would involve performing hand calculations. the problem with this approach is that these calculations do not take the geometry and special features of the building into account. for these reasons, zwp frequently performs a flovent simulation as part of the design process. flovent can calculate and graphically illustrate complete 3d airflow patterns, including velocities and distributions of variables such as pressure and temperature. engineers are then quickly able to evaluate the performance of alternative equipment configurations.

"flovent is designed specifically for modeling building heating and cooling applications, so it is easier, faster and more accurate than general-purpose cfd software when applied to this type of problem," said alfred wallau, a zwp engineer. "i have also received excellent technical support from flomerics whenever i have had a question or problem in using the software."

wallau modeled the building based on the computer-aided design drawing provided by the building designer. he integrated the known values for thermal load and surface temperature into the flovent model of the pavilion, and used both natural and forced ventilation to drive the flow of air through the building. in the case of natural ventilation, air enters and leaves the building through fixed-pressure inlets and outlets. fixed-flow devices with specific flow rates and air temperatures were used to simulate forced ventilation.

"the cfd simulation showed that the design provided comfortable conditions inside using natural ventilation at ambient temperatures up to 24^oc," wallau said. "above this external temperature, air conditioning was needed. the simulation indicated that the original design and position of the grilles was unable to ensure comfortable temperatures and airspeeds. we modified the original design by increasing the size and changing the position of the grilles and found a configuration that provided comfortable conditions even during hot summer days. the final configuration provided stable thermal layering with comfortable temperatures in the inhabitant volume and high temperatures in the higher zones under the ceiling"

wallau also modeled the pavilion under winter conditions. under the coldest expected conditions, the simulation results showed that the use of convection heating at the floor level provided sufficient heating when the pavilion was used for exhibitions. on the other hand, if the pavilion were to be converted to office use, then further heating would have to be provided. "flovent simulation helped ensure that our design provided a comfortable environment for the occupants under the full range of weather conditions, avoiding the need for expensive post-construction modifications," wallau concluded.

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