A spherical experimental device placed in a cylindrical hall of diameter 43 m and height 44 m was used to measure the radiation signal. Photomultiplier tubes (PMTs)

which is used to receive the signal

were installed on the exterior surface of the sphere. The PMTs generated heat at 200 kW during operation. To maintain the surface temperature of the sphere at (21±1) ℃

a method for high-precision temperature control by immersing the sphere in circulated water and distributing water up and down simultaneously was proposed. A simulation method using computational fluid dynamics was applied to analyze the temperature field of the water. The results showed that the method of distributing water up and down simultaneously can achieve a precise local temperature control in large spaces. Owing to the limited flow channels in the irregular cavity

the angle of inclination for both upward and downward water distributors of the circulating system was adjusted to improve the performance of temperature control locally. The increase in the area with a low temperature using the upper water distributors can be up to 20%. To reduce the vertical temperature difference of the water

the water flow ratio of the upper and lower water distributors was increased. The temperature requirement can be met when the water flow ratio is 2.5:1.The water volumes that are effectively cooled are the porous media layer and outer water layer. To obtain temperature profiles with an accuracy of (21±1) ℃ under various heating intensities

the heat flux of the heating sources was determined. The variation ranges of the low-temperature volumes around the upper water distributors differed from that around lower water distributors of the inner water layer. The low-temperature volumes around the water distributors at the top decreased by 41%

while the volumes around the distributors at the bottom decreased by 62%. However

the low-temperature volumes around the lower water distributors were larger than those at the upper water distributor

regardless of the amount of heat flux from the heating sources.