Compressors are defined as the heart of industrial cooling gas cooler groups (chiller) and air conditioning systems. Compressors can be generally classified as positive compression compressors and centrifugal compressors. There are also several types of positive compression compressors. These are piston/reciprocating (angle, semi-hermetic and hermetic), rotary, helical (screw) and scroll type compressors.
Piston compressors ensure suction and compression by means of a moving piston. This type of compressors is preferred in devices that require more power. Rotary type compressors operate with a rotary motion instead of a piston, they are used in devices operating with small power since they are inefficient at high discharge pressures. Helical (screw) type and centrifugal compressors are preferred in systems that require very high power due to their design and cost. Scroll type compressors consist of two spirals called Archimedean spiral and have high cooling efficiency despite their low electricity consumption.
Due to the constant increase in the prices of electrical energy used in production, it is important to utilize the energy used in the devices efficiently. This situation shows itself as the preference of those with low energy consumption and high efficiency in device purchases. In the light of this information, scroll type compressors used in cooling groups draw attention with their low energy consumption and high efficiency.
Scroll Type Compressors
Scroll type compressors are forced compression machines that have been developed and started to be used in recent years, and they consist of two spiral plates (Archimetic spiral), one of which is fixed and the other rotating in the form of a satellite and operating with narrow tolerance intervals. During compression, one of the spirals (top) remains stationary while the lower spiral moves orbitally as it is mounted on the eccentric part on the rotor. When the compressor starts, the gas volume taken between the spiral from the outermost part is translated towards the slot as a result of the rotational movement and then supplied to the discharge line from the hub.
Advantages of Using Scroll Type Compressors
Efficiency
Compressor is the machine considered in determining the efficiency of the cooling system. The efficiency (COP) of a cooling system is equivalent to how many kW of cooling is obtained when the compressor consumes 1 kW of energy. In other words, it is the ratio of the cooling capacity to the compressor power. In order for the cooling efficiency to be high, the compressor must perform a lot of cooling with less energy.
Most of the energy used by the cooling system is consumed by the compressor. In addition, the energy loss will increase as the number of moving parts in the compressor increases. Hermetic and semi-hermetic compressors consist of 9 parts. During the suction and compression of the refrigerant, some of the energy is consumed for moving these parts. There are two parts that perform the compression process in scroll type compressors. Very little of the energy is consumed on these parts while the majority is used for compression.
Another important issue affecting efficiency is the expansion losses that occur during idle times of the pistons in piston compressors in addition to the expansion losses that occur in the suction valves. Since there are no pistons and valves in scroll type compressors, these losses cannot be mentioned, and 100% volumetric efficiency can be achieved while the amount of energy used is reduced.
Reliability / Safety
One of the most lethal incidents experienced in refrigeration applications is the occurrence of an incident called refrigerant explosion which is the coming of refrigerant to the compressor due to the fact that it cannot evaporate in the required amount in the evaporator on the return. This situation can cause great damage to the compressor due to the incompressibility of refrigerants. Gas compression spirals of scroll type compressors have axial and axial elasticity properties. Thanks to this elasticity feature, scroll type compressors have the ability to operate under different abnormal conditions, even in case of refrigerant coming to the compressor
Noise / Vibration
Scroll type compressors have the feature of working without noise and vibration due to their simple design and the fact that they do not need suction valves for compression. Sound levels of Scroll type compressors are lower than hermetic and semi-hermetic compressors at low (160hz-400hz) and high (1000hz-400hz) frequency values.
Size and Weight Comparison
Scroll tip kompresörler; özel yapıları ve dizaynları sayesinde yarı-hermetik ve hermetik kompresörlere oranla soğutma verimleri daha yüksektir. Soğutma etkilerinin yüksekliğine karşın, kapladıları hacim bakımından diğer kompresörlere oranla boyutları oldukça küçüktür. Bunun sebebi; gaz sıkıştırma işlemi için daha az parçaya ihtiyaç duymalarıdır. Scroll bir kompresör aynı kapasitedeki bir yarı hermetik kompresörden %80 daha az parçadan oluşur. Daha az parçadan oluşmaları sebebiyle ağırlıları diğer kompresörlere daha azdır. Şekilde 6 beygir gücündeki Scroll ve yarı-hermetik tip kompresörün karşılaştırılması görülmektedir.
Sonuç
In today’s world, where production costs are increasing more and more, cost effective use of energy is of great importance. In companies that need industrial cooling, the electricity consumed by gas cooling groups (chiller) has an important role in the total electricity consumption of the company. For this reason, meeting the cooling needs with less energy consumption in cooling applications brings with it a significant financial saving. Compressors consume most of the energy consumed by cooling groups. Therefore, new approaches have been developed on the compression of the refrigerant as a result of the studies on compressors. One of the compressors produced with the new compression approach is the so-called scroll type compressors. Scroll type compressors are used in cooling groups due to their advantages such as their cooling efficiency being higher than semi-hermetic and hermetic type compressors, more reliable, safer, vibration-free and quieter operation, less space occupancy and low weight. Although its cost is higher than other compressors, the cost disadvantage loses its importance due to the energy savings it provides and the fact that there are no long-term malfunction problems
Eraco Chiller produces with scroll type compressors up to 440.000 kcal/h capacity, especially in 4-tandem device versions. In this way, it maximizes the compressor risk distribution in the device while high COP and EER values are guaranteed.
KAYNAKÇA
MINISTRY OF NATIONAL EDUCATION PUBLICATIONS, no:2702 Volume 1, Refrigeration and Air Conditioning Nuri ÖZKOL, Applied Cooling Technique
COPELAND Compressors Manufacturer Technical Documents
