heat reservoir

A heat reservoir is a large system that can absorb or release heat without significantly changing temperature. It acts like an ideal thermal sink or source, maintaining a constant temperature regardless of small heat exchanges. Think of it as an extensive body, such as a large pool or the atmosphere, capable of providing or absorbing heat without its own temperature fluctuating noticeably. In thermodynamics, reservoirs are used to analyze energy transfer processes, simplifying calculations by assuming their temperature remains constant during interactions.