Whose work explained how entropy gives heat engines a limit to efficiency?

Nicolas Léonard Sadi Carnot analyzed the operation of ideal heat engines in 1824. He showed that there is a fundamental limit to how efficiently heat can be converted into work, which later became central to the second law of thermodynamics and the concept of entropy. Although Carnot worked before the full modern theory of energy was developed, his ideas remain foundational in physics and engineering. The Carnot cycle is still a standard model for ideal engine efficiency.