Energy saving during bulb storage applying modeling with computational fluid dynamics

Tulip bulbs to plant the next season are stored in containers which are ventilated to a level of 500 or 300 m 3 per m 3 bulbs per hour to avoid high ethylene concentration between the bulbs. In this study a commercial CFD code was used to investigate the distribution of air flow between the containers and the potential energy saving by applying simple solutions concerning the design of the air inlet area and the adjustment of the ventilation rate. By doing so we calculated a variation of container ventilation between 60 and 180%, where 100% is the average flow through the containers. Various measures for improvement were investigated. By smoothing the sharp corners of the entrance channels of the ventilation wall about 7% energy can be saved. The most effective and simple way for improvement, was by covering the open top containers. In this case the variation is between 80 and 120%. By adjusting the overall ventilation to the container with the minimal air flow acceptable in the current situation (67%), energy saving is about 38%. Keywords: Ventilation rate, one layer storage system, ethylene concentration, tulip bulbs INTRODUCTION In The Netheralnds, at 1998, the flowerbulb sector had established an energy consumption agreement with the Dutch Government in order to achieve an increase to energy efficiency of 22% in 2005 compared to the level of 1995, together with a contribution of at least 4% sustainable energy, (Van Bruggen 2002). The Dutch flower bulb industry is highly dynamic. From 1990 to 2003 the number of enterprises was reduced by 33% while farm size increased by 50%. Even if the increase of scale reduced production costs per unit, the demand for environmental protection and improved working conditions also affects the production systems (Wildschut et al., 2005). Tulip bulbs to plant the next season firstly are dried and then stored in containers which are ventilated. During both processes air conditions are controlled by ventilation. Both temperature and humidity should be kept low but the most critical parameter is the ethylene concentration. Ethylene acts as a ripening hormone and high concentrations lead to drastically quality loss, (De Munk 1972; De Wild et al., 2002; Kamerbeek and De Munk 1976). During storage, tulip bulbs are ventilated constantly. Ideally the ventilation rate should be equal through each box. However, differences can be observed pretty easy from the differences in