Temperature precision control is one of the most critical issues in metrology laboratories, and this issue has become increasingly stringent in modern society. Radiant air conditioning system, which minimizes vibration through radiant heat transfer instead of conventional convection, has gained attention but is more sensitive to temperature fluctuations from the cooling source. Considering that phase change materials (PCMs) have the advantage of suppressing water temperature fluctuations, comparative simulations are carried out to analyze the suppressing effectiveness by adding two typical PCMs (paraffin and dimethyl sulfoxide) in water tanks and radiant panels separately. Results indicate that adding paraffin to water tanks has a better effect than dimethyl sulfoxide while it is inverse for radiant panels. Then, the adding volume ratios (paraffin for the water tank is 0.2; dimethyl sulfoxide for radiant panels is 0.1) are provided, when surface temperature fluctuations of radiant panels are suppressed within ±0.1 K. Finally, the relationship between the latent heat/thermal conductivity of PCM versus suppressing effect is investigated to provide a reference for the design of radiant air conditioning systems in metrology laboratories.

Fundamental metrology is closely tied to scientific advancement and requires well-equipped facilities to achieve low measurement uncertainty in rigorous experiments. Addressing the ±0.1 K high-stability temperature control issue of the precision laboratory radiant air conditioning system, this study investigated the influence of different radiant panel area ratios, laying methods, cold source water supply temperature fluctuations, and external environmental disturbances by simulations. The results indicate that: (1) the larger the ratio of radiant panel area, the greater the fluctuation in equipment surface temperature; (2) the surface temperature of the measurement equipment can satisfy ±0.1 K control temperature stability requirement when the fluctuations of the surface temperature of radiant panels and glass window are within ±0.5 K and ±1 K respectively without radiant panels on the ceiling; (3) the surface temperature of the measurement equipment can satisfy ±0.1 K control temperature stability requirement when the fluctuations of the surface temperature of radiant panels and glass window are within ±0.2 K and ±2 K respectively with radiant panels on the ceiling. This study provides a reference for the design and operation control of air conditioning systems in fundamental metrology.