Wind tunnel experiments modelling the thermal effects within the vicinity of a single block building with leeward wall heating

A wind tunnel model aiming to simulate the thermal effects within the vicinity of a building with leeward wall heating was set up. The work was conducted within the scope of the European ATREUS project (http://aix.meng.auth.gr/atreus) in which micro-scale numerical models were used to obtain data concerning the microclimatic conditions within the vicinity of buildings [A.M. Papadopoulos, N. Moussiopoulos, Towards an holistic approach for the urban environment and its impact on energy utilization in buildings: the ATREUS project, J. Environ. Monit. 6 (2004) 841–848]. This data was then used as input data for generating typical weather data required as input for building and heating, ventilation and air-conditioning (HVAC) system models in order to study the energy budgets of buildings and assess the performance of air-conditioning (A/C) systems. However, it was first necessary to validate these microscale numerical models for a simplified case under different thermal conditions. A series of wind tunnel experiments were conducted in which the mean velocity and temperature field within the vicinity of a single block building (a cube) with leeward wall heating were measured. The ratio of Grashof number to the square of Reynolds number, Gr/Re2 was used to model thermal effects within the vicinity of the model, but some compromises were needed in order to obtain a practical model while at the same time fulfilling the objectives of the task set. Conditions representative of mixed and forced convection were modelled. Results showed some degree of flow modification within the recirculation region of the model for both Gr/Re2∼0.9 and 1.6, the recirculation length in both cases being shortened when compared to the non-heated case. The velocity field influenced the temperature distribution within the recirculation region. There was a rapid temperature drop away from the surface, with the temperature distribution reaching near ambient conditions within one model height downstream of the heated face for Gr/Re2∼1.6. In spite of the restrictions applied to the physical model, the technique applied showed very good stability and repeatability during the entire measurement campaign producing a reliable data set for the validation of the microscale numerical models.