Experimental evaluation of ice storage inside a helical coil heat exchanger integrated into a R744 refrigeration system.

In this paper, an experimental evaluation of the ice storage inside a concentric helically coiled tube heat exchanger is presented. The main findings will be useful to suggest an efficient integration of the cold storage (CTES) unit into a R744 refrigeration system for food storage in supermarket cabinets. The free space at the top of the cabinets will be valuable to house the CTES and make good use of the thermosiphon working principle to operate the cold discharging process. The cold charging process is carried out through a CO2 trans-critical refrigeration system. For cold discharging, the CTES is connected to a glycol loop through a double-pipe helically coiled tube heat exchanger (HEX) to simulate the supermarket cabinets. The HEX consists of a three concentric helically coiled tubes of different diameters in order to maximize the heat transfer surface. The coils have the same length in order to ensure the same pressure drop at the HEX outlet and fulfill the thermosiphon circulation conditions. The tests are carried out under different heat transfer fluid (R744) flowrates and temperatures. The cold storage characteristics are investigated.