水冷冷水机组测量不确定度研究

Measurement Uncertainty Research for Water-cooled Chillers

测量不确定度对水冷冷水机组的性能检测具有重要意义,本文选取名义制冷量为850k W的水冷冷水机组为研究对象,以GB/T 10870-2014规定的液体载冷剂法和机组热平衡法为主要试验和校核试验方法,建立测量不确定度评定模型,对实测结果的测量不确定度进行了评定,并分析了直接测量参数对不确定度的影响趋势。结果表明:进出口水温是影响测量不确定度评定的最主要因素,在温度测量系统精度为0.05℃、流量测量系统精度为0.5%时,进出口水温对合成标准不确定度的分项占比高达67.5%,如果将测温精度分别更改为0.08℃和0.1℃,则主侧制冷量的相对不确定度将从1.8%提升到2.7%和3.3%,辅侧制冷量的相对不确定度将从2.2%提升到3.4%和4.2%。

Measurement uncertainty is of significance in performance testing for water-cooled chillers. This article selects water cooled chillers with 850kW of nominal cooling capacity as its study objects, and adopts the liquid refrigerant method and the heat balance method as its testing and checking methods in accordance with the provisions of GB/T 10870-2014. Based on the evaluation model, the uncertainty obtained by tests is assessed, and the effect of trends of all di-rect measured parameters on uncertainty are also analyzed. The results show that the inlet/outlet water temperature is the most important factor affecting uncertainty measurement. When the precision of temperature and flow rate measuring is 0.05℃ and 0.5% respectively, the inlet/outlet water temperature contributes up to 67.5% to the combined standard uncer-tainty. If the temperature measuring precision is modified to 0.08℃or 0.1℃, the uncertainty of evaporator cooling capacity will increase from 1.8% to 2.7% or 3.3%, and that of condenser cooling capacity will increase from 2.2% to 3.4% or 4.2%.