A cooling tower is a heat rejection device which rejects waste heat to the atmosphere through the cooling of water to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and cools the working fluid to near the wet-bulb air temperature.
And in Other hand, A heat exchanger device is use in transfer of heat between a solid object and a fluid, or between two or more fluids. Heat Exchanger are widely use in space heating, refrigeration, air conditioning, power stations, chemical plants etc. You can check verious types of cooling tower and Heat Exchanger and it's specification at official sites.