Capacity control for screw-compressor chillers
Capacity control is in high demand for many cooling systems where cooling loads are not constant, and adjusting the system’s capacity to meet the prevailing load is essential for optimum efficiency. Efficiency primarily depends on compressor suction and discharge pressures, with the influence of secondary factors like useful and non-useful superheat and subcooling. As the screw compressor unloads, its suction pressure lowers (at the fixed condensing temperature), and efficiency decreases. Capacity control mechanisms allow maintaining the desired suction pressure by adjusting the refrigerant flow through the compressor.