Energy regulation method of screw chiller unit

Screw chiller is a chiller unit that uses various forms of screw compressors as the main engine. In general, users will choose the capacity of the compressor for a screw chiller based on the actual cooling capacity under working conditions. However, due to changes in ambient temperature and application load, it may be necessary to adjust the compressor's gas delivery to match the actual heat release, in order to achieve the goal of economical operation of the chiller. Here, the Jimes Refrigeration editor will take you to understand how the energy regulation function of screw chillers achieves energy-saving operation of the unit.

The energy regulation function we refer to is that industrial chillers can automatically adjust the input power of the compressor based on the load size (the amount of heat released by the cooled equipment), reducing unnecessary energy consumption. The commonly used energy regulation functions can be adjusted through two methods: slide valve regulation and plug column valve regulation. In addition, there are also methods such as frequency conversion regulation, turn stop regulation, and refrigerant suction throttling regulation. Here we mainly introduce the first two methods:

Sliding valve energy regulation method

The specific method is to install an axially movable slide valve between the two rotors in the screw compressor. When the slide valve moves axially, a bypass hole is formed in the radial direction of the rotor, allowing the gas that has been sucked into the screw to flow back to the suction chamber through the bypass hole without compression. The reflux rate of gas increases with the increase of the axial movement distance of the slide valve, which reduces the gas delivery capacity of the compressor even more. The slide valve can continuously adjust the gas transmission volume within the range of 10-100%. But when the slide valve adjusts the gas transmission volume below 50%, the performance coefficient will correspondingly decrease significantly, which appears to be economically poor.

Energy regulation method of plunger valve

Screw compressors can use solenoid valves to control the opening and closing of plug valves to achieve staged regulation of gas transmission. Nowadays, most screw chillers can achieve gas transmission regulation of 33% -66% -100% or 25% -50% -75% -100%.

The use of slide valve or plunger valve mechanism for energy regulation can also enable the compressor to start under no-load or low load to reduce the impact of starting current.

These characteristics are widely used in various industrial and commercial applications. By using a single or multiple compressor refrigeration system, screw chillers can cover refrigeration capacities ranging from 100kw to 3B.