Experimental and numerical study on water ice forming on pipe columns in a limited-volume storage

Abstract

Draft beverage is mostly cooled with a direct expansion refrigeration system equipped with ice bank thermal storage in the form of a bath and coiled heat exchangers for beverage cooling. This study conducts a numerical simulation and experimental validation of the ice bank forming inside the experimental model of a draft beverage cooler with a natural convection flow. Key design parameters of the test rig were water bath dimensions, number of pipes, pipe diameter and its position inside the water bath, as well as the initial water temperature in the pull-down time process. These were chosen to be as close as possible to the properties of a real draft beverage cooler. Furthermore, glycol solution was used instead of a refrigerant to provide approximately constant inner pipe temperatures during the experiments corresponding to refrigerant temperatures in the real draft cooler operation. Experimental validation is carried out by comparison of temperatures inside the water bath, profile of formed ice mass, and heat flow on pipes. Comparison of the mass of formed ice under different temperatures of glycol solution was performed to validate the simulation model in the conditions of variable evaporation temperature of the refrigerant as prevailing in real refrigeration units. The results obtained by the simulation are in a good agreement with results obtained by the experiment. This study is part of a comprehensive research on energy efficiency of draft beverage coolers. The simulation model validated in this study is developed with intention to be a part of a broader simulation system for analysis of the complete refrigeration system of the draft beverage cooler.