The Laser-Imaged Natural Circulation (LINC) facility is an experimental apparatus designed for the observation of natural circulation phenomena associated with vertical, heated cylinders. Continuous operation of natural circulation flow is made possible by a cooling plate that makes up the top of an acrylic tank, designed to allow heater rods to pass through in configurations that include two 3/8” rods with variable pitch or one rod with variable diameter. It leverages Particle Image Velocimetry (PIV) as well as an array of thermocouples to measure heat transfer and time-resolved fluid velocity. From these measurements, deductions can be made about boundary layer thickness, heat transfer rate, boundary layer transition location, time-resolved velocity profiles and more.

The purpose of the LINC facility is to provide valuable data in support of furthering understanding natural convection in this geometry. It is of particular interest to the nuclear engineering field as the majority of nuclear fuel in use in the world consists of long, slender cylinders which are immersed in water and cooled via natural convection for much of its life. The data acquired from the LINC facility can be applied directly to safety and performance assessment models used to maintain nuclear fuel at safe temperatures at all times.

The LINC facility allows for investigations using two rod configurations with variable pitch as well as one-rod configurations with variable rod diameter. The maximum power that can be supplied to each rod (and removed by the cooling plate) is 1,400 W, powered by a digital power supply with feedback of actual power used. Velocity field data can be collected using the PIV system at frequencies of 5,000 Hz. Temperature is monitored at many locations including inside the tank, internal to the heater rod(s) and at the inlet and outlet of the cooling plate. The chiller that circulates coolant through the cooling plate has a rating of 1,700 W at 20°C. The tank operates at atmospheric pressure.

Front view of LINC facility in operation in a two-rod configuration.

Sam Goodrich and the front view of the LINC facility in operation in a two-rod configuration.

 

Surface plot of velocity profile for channel between two heated rods

Surface plot of velocity profile for channel between two heated rods.