A heat exchanger that includes an input cavity defined by inlet cavity walls; a heat exchanger portion in fluid communication with the input cavity and defined between a first side and a second side, and wherein a plurality of baffles are positioned within the heat exchanger portion; and an outlet cavity in fluid communication with the heat exchanger portion and defined by outlet cavity walls. The heat exchanger portion comprises: a plurality of first fluid paths defined between the baffles and extending from the input cavity to the outlet cavity, and a plurality of tubes extending through the heat exchanger portion from the first side to the second side. Each tube extends through the baffles so as to define a second fluid path through the heat exchanger portion. Heat exchanger systems are also generally provided, along with methods for cooling a hot fluid input with a heat exchanger.