Presentation on theme: "MODELING AND ANALYSES OF EVAPORATIVE COOLING EFFICIENCY FOR MIST-FOG SYSTEMS Ta-Te Lin, Yi-Chung Chang Department of Agricultural Machinery Engineering,"— Presentation transcript:
MODELING AND ANALYSES OF EVAPORATIVE COOLING EFFICIENCY FOR MIST-FOG SYSTEMS Ta-Te Lin, Yi-Chung Chang Department of Agricultural Machinery Engineering, National Taiwan University, Taipei, Taiwan, R.O.C.
l INTRODUCTION l MODEL DEVELOPMENT l SIMULATION AND ANALYSES l CONCLUSIONS
INTRODUCTION n EVAPORATIVE COOLING AND ITS APPLICATIONS n FACTORS AFFECTING EVAPORATIVE COOLING n OBJECTIVES
FACTORS AFFECTING EVAPORATIVE COOLING n RELATIVE HUMIDITY n AMBIENT TEMPERATURE n DROPLET SIZE n VENTILATION RATE n DROPLET TRAVEL DISTANCE
OBJECTIVES To develop a theoretical model for the calculation of evaporative cooling efficiency base on mass transfer and particle dynamic theories. To validate the model with existing laboratory data. To analyze the influences of selected parameters, such as temperature and relative humidity, on the evaporative cooling efficiency of mist-fog systems.
MODEL DEVELOPMENT n MASS TRANSFER OF DROPLETS n PARTICLE DYNAMICS n CALCULATION OF PSYCHROMETRIC PARAMETERS
MASS TRANSFER OF DROPLETS The Goering Model: The Basic Mass Transfer Equation:
Diffusivity MASS TRANSFER OF DROPLETS Pressure Difference Partial Pressure of Air Pressure Difference
PARTICLE DYNAMICS Particle Motion: Drag Force Calculation:
Effect of Wind Direction and Droplet Moving Angle: Effect of Spray Nozzle Gauge Pressure: PARTICLE DYNAMICS
CONCLUSIONS A theoretical model to predict evaporative cooling efficiency for mist-fog systems was established based on mass transfer theory and particle dynamics. The model was validated with experimental data from existing literature and the predicted evaporation efficiency agreed well with the measured values. The effects of temperature, relative humidity and the size of spray droplet on the cooling efficiency of mist- fog systems were analyzed with the developed model. Useful information can be generated with model simulations as an aid in designing effective mist-fog systems.