Abstract: The invention provides in one of its aspects a thermal storage heat exchanger. The heat exchanger receives through a first input a slurry of fine ice particles in an aqueous solution having a concentration below its eutectic concentration, the ice particles and solution being stored in said heat exchanger as a porous ice bed and a substantially ice-free liquid bath. The heat exchanger also receives heated aqueous solution through a second input and discharges liquid phase refrigerant through the first output. Distribution means are locatable above said ice bed within the heat exchanger to distribute the heated solution evenly through the porous ice bed.