受热 is a separable verb (离合词) with two distinct senses: (1) 'to be heated' — used for materials or substances that absorb heat, and (2) 'to suffer heatstroke' — a medical condition from prolonged heat exposure. You can split it by inserting 了, 过, or a measure phrase between the two characters, e.g., 受了一次热 ('was heated once' / 'suffered a heatstroke once'). The contexts are usually different: cooking, science, or industrial processes for the 'heated' sense, and outdoor work or extreme weather for 'heatstroke'.