Difluoromethane (HFC-32, DFM), with a global warming potential (GWP) of 677, is of interest as a pure refrigerant and as a component in low-GWP refrigerant mixtures. Additionally, difluoromethane has recently been identified as a safe, liquefied-gas electrolyte material in batteries. Using state-of-the-art instruments for measurements, this paper presents new liquid-phase speed of sound and vapor-phase density data for difluoromethane. Two hundred and nine liquid-phase speed of sound values were measured using a dual-path pulse-echo instrument at temperatures from 230 to 345 K and pressures from 2.1 to 70 MPa. Accounting for all sources of uncertainty, the relative expanded combined uncertainty (k = 2) in the speed of sound ranged from 0.035 to 0.17%. One hundred and thirty-eight vapor-phase density values were measured using a two-sinker densimeter at temperatures from 240 to 340 K and pressures from 0.1 to 1.61 MPa with an uncertainty of 0.011 to 0.12%. These experimental data will be valuable in the ongoing development of a new fundamental thermodynamic equation of state for difluoromethane.

中文翻译：

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二氟甲烷的液相声速和气相密度

二氟甲烷 (HFC-32, DFM) 的全球变暖潜能值 (GWP) 为 677，作为纯制冷剂和低 GWP 制冷剂混合物中的一种成分备受关注。此外，二氟甲烷最近被确定为电池中安全的液化气体电解质材料。本文使用最先进的仪器进行测量，展示了二氟甲烷的新液相声速和气相密度数据。使用双路脉冲回波仪器在 230 至 345 K 的温度和 2.1 至 70 MPa 的压力下测量了 209 个液相声速值。考虑到所有不确定性来源，相对扩展的组合不确定性（k= 2) 在声速范围内从 0.035 到 0.17%。在 240 至 340 K 的温度和 0.1 至 1.61 MPa 的压力下使用双沉孔密度计测量了 138 个气相密度值，不确定度为 0.011 至 0.12%。这些实验数据对于不断开发新的二氟甲烷基本热力学状态方程非常有价值。