Influence of office layout and ceiling height on vertical temperature gradient in office rooms with displacement ventilation

An accurate temperature gradient calculation is essential for displacement ventilation (DV) system design, since it directly relates to the calculation of supply air flow rate. Several simplified nodal models were developed and implemented in the various building simulation programmes in order to estimate the temperature stratification in rooms with displacement ventilation. However, the most commonly used models do not count the types and locations of the typical heat loads in rooms with displacement ventilation. As a result, the calculated air temperature in the occupied zone can defer from the real one, which causes poor thermal comfort and inadequate sizing of the ventilation system.
In the present study, five simplified nodal models are analysed and validated with the experimental results in two measurement setups. In addition, the effect of the room heights and locations of the indoor heat sources were studied for the typical office environment. The experiments demonstrate that displacement ventilation provides even temperature gradient throughout the simulated office room spaces. The influence of the room height on the vertical temperature gradient is significant in the cases with high-level heat loads. The novel nodal model demonstrates an accurate calculation of the temperature gradient for the typical heat loads office layouts.