完美的气体模型

The perfect gas model is a refinement and simplification used extensively in thermodynamics and 流体力学. While the 理想气体定律, [latex]PV=nRT[/latex], only assumes negligible intermolecular forces and molecular volume, the perfect gas model adds the constraint that the specific heats at constant pressure ([latex]C_P[/latex]) and constant volume ([latex]C_V[/latex]) are constant. This additional assumption is crucial because it implies that the internal energy ([latex]U[/latex]) and enthalpy ([latex]H[/latex]) are solely linear functions of temperature. Specifically, [latex]dU = C_V dT[/latex] and [latex]dH = C_P dT[/latex].

对于单原子气体（如氦、氩）和双原子气体（如氮、氧），在振动模式未受到显著激发的中等温度范围内，这种简化方法相当准确。然而，对于多原子气体或在较宽的温度范围内，比热会发生变化，这时需要更通用的半理想（或热理想）气体模型。理想气体模型是热力学概念教学的基础，并为许多实际工程问题（尤其是在气体动力学和推进系统分析中）提供了一阶近似。