Comparison of simplified models to estimate vertical temperature gradient in rooms with displacement ventilation

Vertical temperature gradient prediction is essential for displacement ventilation system design, since it directly relates to the calculation of supply air flow rate. Several simplifid 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 error between the calculated with the commonly used models and measured temperature in the occupied zone can reach 2-3C. It results in poor thermal comfort and inadequate sizing of the displacement ventilation system.

The aim of the study is to compare four commonly used simplified models and a novel nodal model to calculate the temperature gradient in a room with various single flow elements and combinations of them. The measurement data were compared with the existing nodal models and the proposed novel nodal model in terms of predicting the occupied zone tempereratures. The proposed nodal model provides a simplified and accurate technique to predict the temperature gradient for typical indoor heat loads.