The invention relates to a heat exchanger with inter-connecting cells in a row or block which evenly distribute and transfer heat to a fluid within a cell. Voids between rows or blocks of cells and the heat transfer medium comprise additional means of transferring heat from a heat-transfer medium to the fluid within the cells. The heat exchanger may be used but not limited to applications such as a condenser in an air conditioning unit, a wall heater or an indirect evaporative cooler.