1, different refrigeration capacity
Screw machine: a single screw compressor refrigeration centrifugal machine is smaller, generally from 30RT to 500RT, so now the big refrigeration screw chiller are used in the way of multi-head, by the microcomputer unified control, regulation, and each compressor has a separate refrigeration system.
Centrifugal machine: the refrigeration capacity of a single centrifugal compressor is larger, from 150 to 3000RT, so generally centrifugal refrigeration machine is designed only a centrifugal compressor can meet the needs of the cold capacity.
2, two kinds of compressor rotation and transmission part of the structure of different characteristics
Centrifugal machine: motor through a pair of gears to drive the impeller for high-speed rotation.
Screw machine: the motor directly together with the main rotor and vice rotor meshing with each other for low-speed rotation.
Comparison:
As can be seen from the above, the screw compressor structure is more simple, and centrifugal impeller rotating speed is much higher than the screw rotor, while the high-pressure gas on the blade, impeller have a greater impact pressure, so its failure rate is obviously higher than the screw machine.
At the same time, the centrifugal compressor due to the complex compressor structure, in the maintenance and repair is very troublesome, while the screw unit structure is simple, maintenance and repair is very convenient.
3, the two models have different capacity adjustment range
Centrifugal: Generally speaking, the energy adjustment range of centrifugal unit is 40～100%, in less than 40% load operation, centrifugal unit is more prone to ‘wheezing’ phenomenon, ‘wheezing’ is serious, it can make the whole core component of the unit – impeller is damaged, make the centrifugal unit – impeller is damaged, make the centrifugal unit – impeller is damaged, make the centrifugal unit – impeller is damaged. -The impeller is damaged and the centrifugal compressor is scrapped.
At present, many centrifugal unit manufacturers through the ‘make-up air’ means is the unit ‘wheezing’ critical point to ‘20%’ or ‘10%’, and the ‘wheezing’ of the unit to achieve ‘20%’ or ‘10%’, and the ‘wheezing’ of the unit to achieve ‘20%’ or ‘10%’. ‘and’ make-up ’is required to consume a lot of energy, so that the unit below 50% efficiency is relatively low.
Screw machine: screw machine is the use of oil pressure to push the slide valve switch to control the capacity, part of the load, there is no unbalance impact phenomenon. For screw units with multiple heads, the energy adjustment range is generally between 7.5 and 100%, and continuous energy adjustment is possible.
Especially in civil and commercial places, such as hotels, shopping malls, conference centres, etc., the air-conditioning load varies greatly with seasonal changes and changes in the flow of people, which requires refrigeration units to have a wider range of energy regulation.
4, the two models of maintenance and cost differences
Centrifuge: generally speaking, the centrifuge is a single compressor form, maintenance, repair, the whole machine needs to be closed, stop the refrigeration operation. Complex structure, more wearing parts, maintenance costs are higher.
Screw machine: screw machine is a multi-compressor form, and has an independent refrigeration system, so that in the maintenance, repair state, screw machine only a single compressor off, the other work as usual, to meet the needs of the building load. Unit structure is simple, less wearing parts, maintenance costs are also lower.
5, the impact of the two models of different power grids
Two models of power consumption, but because of the same refrigeration capacity, screw machine using multiple compressors, can be started step by step, the starting current is much smaller than the centrifuge, reducing the impact on the power grid.
6, the two models produce different noise
Screw: screw machine is relying on the Yin, Yang rotor rotation to complete the suction and discharge, its rotational speed is low, generally 2950 rpm, the noise value is generally in the 75 dB (A) or so, and not sharp, and centrifugal units are generally in the 80 dB (A) or more.
Centrifugal type: Centrifugal machine has high rotational speed, generally 9000~40000 rpm, and uses blades and impellers for suction and exhaust, so its noise value is higher than that of screw machine, and it is a bit sharp.