Xiaobai, I have a few questions about compressors

This post was last edited by wuchangjian on 2015-7-23 at 21:52. 1. What kind of compressors require cooling? Is it determined by power, or by some other criterion? Are all of them cooled by water? For example, bearings generate heat during operation; if the design parameters indicate that the amount of heat produced exceeds the bearing’s tolerance limit, then lubricating oil must be added to cool it down ； When a compressor compresses a medium, the medium heats up; therefore, a cooler is required at the compressor’s outlet (depending on the specific outlet temperature). In reciprocating compressors, the cylinders and piston rings undergo frictional reciprocating motion, which generates heat, so the cylinders are cooled using circulating water. 2. What does the number 3 in the Z3W type piston compressor represent? There are many ways to identify compressors. The type you mentioned seems to refer to very small compressors; I haven’t noticed them before, but you can search on Baidu. 3. Why are piston compressors not allowed to have liquid in the intake air? A reciprocating compressor uses gas compression to generate power; during the compression process, the gas is subjected to extremely high forces, resulting in its instantaneous compression ； However, liquids are incompressible; if a liquid is mixed into a gaseous medium, during compression the liquid is subjected to extremely high forces instantly, and it is propelled away like a bullet, leading to many serious accidents such as cylinder collisions.

Compressor cooling generally cools the compressed medium, lubricating oil, and the motor. 1. Generally, compressors can be classified according to their principle into various types such as piston compressors, centrifugal compressors (turbine, water ring, turbine-type compressors), axial flow compressors, jet compressors, and screw compressors. 2. Based on the position of the compressor cylinders (the centerline of the cylinders), they can be classified as: (1) Horizontal compressors, where all cylinders are horizontal (with the centerline of the cylinders in a horizontal direction). (2) Vertical compressors, with all cylinders arranged vertically (upright compressors). (3) Angular compressors, with cylinders arranged at various angles such as L-shaped, V-shaped, W-shaped, and star-shaped. 3. Based on the arrangement of the cylinders, they can be classified as follows: (1) In-line compressors: Several cylinders are arranged in sequence on the same shaft, also known as single-row compressors. (2) Parallel compressor: Several cylinders are arranged parallel on several shafts, also known as a double-row compressor or multi-row compressor. (3) Compound compressor: A multi-stage compressor composed of both series and parallel configurations. (4) Symmetrically balanced compressor: The cylinders are arranged horizontally on either side of the crankshaft, with the crankshaft journals being 180 degrees apart from each other, forming an H shape; this arrangement allows the inertial forces to be largely balanced. 4. Based on the final exhaust pressure of the compressor, they can be classified as: (1) Low-pressure compressors: with a final exhaust pressure of 3–10 psig. (2) Medium-pressure compressor: The final exhaust pressure is between 10 and 100 psig. (3) High-pressure compressor: The exhaust final pressure is between 100 and 1000 psig. (4) Ultra-high pressure compressors: The final exhaust pressure is above 1000 psig.

Beginners, please try to answer the following: 1. From a thermodynamic perspective, the actual compression process of a gas is a polytropic process; the closer it is to an isothermal process, the less work is required, while the closer it is to an adiabatic process, the more work is needed. Therefore, to make it as close as possible to an isothermal process, the compressed medium is usually cooled between stages. Cooling methods include both air cooling and water cooling. 2. I haven’t seen this one. 3. Since liquids are incompressible, and the clearance volume of reciprocating compressors is very limited, the presence of liquid in such compressors can lead to damage to their mechanical components.

1. The first question might not have been explained clearly; by cooling, I mean the cooling of the compressor bearings and similar components, not just the outlet medium； Since it was found that some systems at the site have oil cooling while others do not, I’m asking. 2. ZW stands for vertical type and oil-free lubrication, but I still haven’t found an answer for 3; it’s indeed a compressor with a low capacity, approximately 3 m3/min. 3. I’m very satisfied with this answer; it’s been educational.

Bearing cooling depends on the circumstances: different operating conditions and speeds, as well as different types of bearings. These conditions determine whether cooling is necessary. I’m glad I could help you. You’re welcome.

For the cooling of bearings, oil cooling is used whenever cooling is necessary; water cooling is not employed. Cold lubricant enters the bearing area to carry away heat. The hot lubricating oil flows out to exchange heat with the heat exchanger outside the compressor.

Well, can it be understood in this way that bearings need to be lubricated as well as cooled, which is why oil cooling is generally used? By the way, by water cooling, do you mean cooling the hot oil in the bearings?

You can think of it this way: oil serves to lubricate and cool. Hot oil and the heat exchanger exchange heat, with water being the common heat transfer medium in heat exchangers.

Z stands for vertical compressor. The 3 columns refer to the arrangement of the compressor cylinders; there are 3 columns in total, which means three pistons and three connecting rods, and in some cases three piston rods as well