Cooling of a compressor shaft gas bearing

A method of operating a heat transfer circuit, the heat transfer circuit including a compressor with a radial gas bearing and a shaft, a condenser, an expander, and an evaporator, the method comprising:

• directing a working fluid through a main flow path of the heat transfer circuit, the main flow path directing the working fluid through the compressor, the condenser, the expander, the evaporator, and back to the compressor, the directing of the working fluid through the main flow path includes rotating the shaft of the compressor to compress the working fluid, the radial gas bearing including an outer radial surface of the shaft and a radial support surface of a housing, the rotating of the shaft causing grooves in the outer radial surface of the shaft to direct gas between the outer radial surface and the radial support surface to form a layer of the gas between the outer radial surface and the radial support surface that radially supports the shaft while rotating, wherein the rotating of the shaft of the compressor to compress the working fluid includes controlling, with a controller, the compressor to rotate the shaft such that a speed of the outer radial surface of the shaft is at or greater than 25 m/s;
• and
• supplying a portion of the working fluid in the main flow path at the condenser, at the evaporator, or between the condenser and the evaporator to the compressor to cool the radial gas bearing, wherein the supplying of the portion of the working fluid to the compressor to cool the radial gas bearing includes controlling, with the controller, a flowrate of the portion of the working fluid supplied to the compressor based on preventing heat in the radial gas bearing from exceeding a predetermined amount,
• wherein the shaft has a radius r at the radial gas bearing, and a radial clearance in the radial gas bearing between the outer radial surface and the radial support surface is at or less than 0.0011 of the radius r of the shaft.