On-site thermometer calibration by the temperature scale transfer technique based on fixed points can effectively improve the calibration level of thermometers in large-diameter hot water pipes. Calibrations of contact thermometers in large-diameter hot water pipes are often carried out using dry block calibrators. Axial temperature gradients and the drift of reference thermometers are the main sources of error for the use of the traditional dry block calibrators. To overcome these disadvantages, a new dry block calibrator with small multi-fixed-point cells was designed in this work to improve the homogeneity of the inner temperature field and calibrate the reference thermometers in situ. The calibrator was based on small multi-fixed points including the melting point of Hg (234.28 K), the melting point of Ga (302.91 K), the melting point of H₂O (273.15 K) and was developed for use in the temperature range from − 50 °C up to 100 °C. The calibrator was designed using thermal Finite Element simulations carried out with COMSOL Multiphysics and has an ectopic multi-fixed-point structure. The melting process of the multi-fixed points was simulated using the effective heat capacity method, and the fraction of the liquid phase for the fixed-point material was obtained at different phase-transition radius values and temperature plateaus of multiple fixed-points cells were obtained at different dT values. The simulation explored the influence of different heating temperatures on the temperature plateaus of multiple fixed-points cells, and the functional relationship between the heating temperature and the temperature plateaus of multiple fixed-points cells was obtained, calculating the error between temperature plateaus and thermometer at different heating power, providing a technical basis for the subsequent prototype experiments and the validation of the prototype design through experimental measurements in future work.

通过基于定点的温度刻度传递技术对温度计进行现场校准，可以有效提高大口径热水管中温度计的校准水平。大口径热水管道中的接触式温度计的校准通常使用干块校准器进行。轴向温度梯度和参考温度计的漂移是使用传统干块校准器的主要误差来源。为了克服这些缺点，在这项工作中设计了一种新型的带有小多点固定单元的干式块校准器，以改善内部温度场的均匀性并就地校准参考温度计。校准器基于多个小固定点，包括Hg的熔点（234.28 K），Ga的熔点（302.91 K），H的熔点₂ O（273.15 K），专为在− 50°C至100°C的温度范围内使用而开发。该校准器是使用COMSOL Multiphysics进行的热有限元模拟设计的，具有异位多不定点结构。使用有效热容量法模拟了多不定点的熔化过程，并在不同的相变半径值下获得了定点材料的液相分数，多个定点单元的温度平稳期为在不同的d T获得价值观。仿真探索了不同加热温度对多个定点电池温度平台的影响，得到了多个定点电池加热温度与平台温度之间的函数关系，计算了温度和温度之间的误差。不同的加热功率，为后续的原型实验和通过未来工作中的实验测量验证原型设计提供技术基础。