R32毛细管流量特性模型计算和诺模图建立

Numerical Calculation and Nomogram of R32 Flow Characteristics in Capillary Tube

毛细管是一种重要的节流元件,广泛应用于各种小型制冷制热装置中,R32作为环境友好型制冷剂,在家用空调领域应用愈发广泛。本文首先基于均相流假设及能量守恒、动量守恒、质量守恒方程,建立绝热毛细管的数学模型,并经适量简化,分别从过冷区和两相区对毛细管模型进行分析求解,得到毛细管长度的计算公式。同时,在该模型中引入了壅塞流概念,采用临界流量作为壅塞流是否出现的判断依据,有效提高了算法精度和稳定性。其次,搭建了针对R32的毛细管测试平台,通过实验获得了内径为1 mm,长度为0.5 m和1 m的两根毛细管在冷凝压力为2.4~3.2 MPa、过冷度为5~20℃下的质量流量数据,验证了该仿真模型的精度。最后,基于仿真模型得到的大量数据点,绘制了R32毛细管的诺模图。

Capillaries are important throttling elements widely used in small cooling and heating devices.R32 is an environmentally friendly refrigerant and is extensively employed in household air conditioning.In this study,a mathematical model of adiabatic capillary tubes was first developed on the basis of homogeneous flow,energy conservation,momentum conservation,and mass conservation equations.The model affords a formula for calculating the capillary lengths in the subcooling and two-phase regions.The concept of choked flow was introduced into the model,and the critical flow was used to assess whether choked flow occurred.The incorporation of the choked flow concept improved the accuracy and stability of the model.Next,a capillary tube test platform using R32 was built to verify the accuracy of the simulation model.The mass flow rates of two capillary tubes with an inner diameter of 1 mm and lengths of 0.5 m and 1 m under a condensing pressure of 2.4-3.2 MPa and a subcooling degree of 5-20℃were obtained.Finally,a nomogram of the R32 capillary was drawn using extensive data points obtained from the simulation model.