Optimization of the humidification of cold stores by pressurized water atomizers based on a multiscale CFD model

Humidification during long-term cooled storage of fruits is being introduced into practice to prevent excessive moisture loss and quality degradation. High pressure fogging is one of the few systems that can be used in ultra low oxygen (ULO) storage rooms. For system design and optimization, a CFD based multiscale model was used. At the smallest scale, the flow through stacked products in boxes was predicted using a direct model that combined discrete element (DE)-CFD modelling. At larger scale, a loaded cool room model that predicts the storage room air velocity, temperature and humidity distributions and fate of the water droplets was developed. The loaded product was considered as a porous medium, where the anisotropic loss coefficients were determined from a combined DE-CFD simulation. A Lagrangian particle tracking multiphase flow model was used. An interval humidification of 1 min on and 15 min off with a water pressure of 80 bar (3.59 L h−1) for a ULO storage room at −1 °C on average gave a relative humidity of 96.3%. The amount of sprayed water deposited on the stack and room surfaces depend on the application pressure and nozzle position and direction. Good agreement was found between measured and predicted results.