Estimation of opening discharge coefficient of naturally ventilated dairy buildings by response surface methodology Abstract   The discharge coefficient (Cd) is a characteristic parameter of an opening, which represents the effect of flow contraction and frictional losses when the flow goes across the opening. It is an important parameter for the ventilation rate determination when using the orifice equation method. The objectives of this study were to investigate the relationship between Cd and its potential influencing factors, i.e. opening ratio (r), building length to width ratio (xcexb1), wind speed (U), and wind direction (xcexb8), and to evaluate the sensitivity of each factor on the Cd for naturally ventilated dairy buildings (NVDBs). The investigations were performed using the response surface methodology together with BoxBehnken Design and Computational Fluid Dynamics simulation methods. A secondorder polynomial response surface model for the estimation of the discharge coefficient was developed and verified. The results showed that the Cd was significantly affected by the individual factors of r and xcexb8, with more sensitivity to r when rxc2xa0u003exc2xa042.5%. By contrast, the effects from the individual factors of xcexb1 and U on Cd were insignificant. In addition, the interaction effects between r and xcexb8, and between xcexb1 and xcexb8 on Cd were also identified. It was concluded that the effects from both individual factors and interactions are required to be considered in the estimation of the opening discharge coefficient for NVDBs.

Flow analysis inside tractor cabin for determining air conditioner vent location Abstract   In this study, thermal comfort was simulated through flow analysis and the air conditioner vent location inside a tractor cabin was determined. The heating test of a tractor in an environmental chamber was performed to obtain temperature data at thermal equilibrium, and this result was used as the boundary condition for the simulation. The properties of the cold air input through the air conditioner vent were obtained through a cooling performance test. The inside of the tractor cabin was modeled, and a grid was created to perform the flow analysis. Predicted mean vote (PMV) and predicted percentage of dissatisfied were used to evaluate thermal comfort, and the temperature, air velocity, and humidity for calculating PMV were simulated. The temperature and PMV measurement locations were based on the temperature measurement positions proposed in SAE J1503.  The locations of the air conditioner vent selected as the simulation target were the ceiling, dashboard, and side column. These locations were selected based on the actual location of the air conditioner vent in the tractor cabin. The flow field with the lowest kinetic energy loss was formed when the air conditioner vent was positioned on the dashboard. In this case, the average temperature was 22.2xc2xa0xc2xb0C, which was 3xc2xa0xc2xb0C lower than that at other locations. In addition, the average PMV was 0.53, which was 1 lower than that at other locations. Based on the results of this analysis, it was found that the most comfortable environment of the tractor cabin was created when the air conditioner vent was located on the dashboard.  This study is the first to evaluate the thermal comfort of agricultural tractors using simulation. The simulated temperature showed a deviation of 2xc2xa0xc2xb0C or less from the measured temperature. This confirms that the simulation model can ensure accuracy. These results show the possibility that simulation can be used for studying thermal comfort.