Structural principle of screw refrigerators

I. Job Tasks and Production Principle 1. Tasks: Pressurize and condense the gaseous ammonia that comes from the ammonia synthesis tower and the ammonia evaporator of the turbine cycle machine, and which cannot be processed further, into liquid ammonia, thereby balancing the cooling load of the entire ammonia system. 2. Principle of production: The process in which a gas is converted into a liquid is called liquefaction, and the temperature at which this occurs is known as the liquefaction temperature or condensation temperature. The condensation temperature of gaseous ammonia increases as pressure rises. At normal pressure and temperature, gaseous ammonia cannot be converted into liquid ammonia; only by using pressure under normal temperature conditions can gaseous ammonia be liquefied. Therefore, it is first necessary to compress the gaseous ammonia to a certain pressure, and then cool it to the liquefaction temperature, after which the ammonia will condense. A screw refrigeration compressor is a rotary positive-displacement compressor that relies on the decrease in volume of the gas as it enters the compressor chamber, which leads to a sharp increase in gas density and thus an increase in the pressure of the gaseous refrigerant. Inside a screw-type refrigeration compressor, there are two parallel rotors that mesh with each other—the male rotor and the female rotor. As the two rotors rotate, their teeth interlock with each other’s tooth grooves. As the rotors continue to spin, the degree of interlocking increases, thereby reducing the volume of the chambers used to hold the gas, and this achieves the purpose of compressing the gaseous refrigerant. To ensure the compressor operates properly, oil must be injected into it. Injecting oil into the compressor’s working chamber serves to provide sealing and cooling effects; lubricant is also required for the operation of bearings, shaft seals, and balance pistons. II. Job Responsibilities 1. Under the leadership of the area supervisor and the shift supervisor, be responsible for the management of the equipment, pipelines, valves, electrical components, instruments, installations, safety facilities, and tools related to this ice machine. 2. Responsible for the startup, shutdown, normal operation, and accident handling of screw chillers. 3. Add sufficient lubricating oil based on the oil level of the ice machine to ensure its proper operation. 4. Adjustments should be strengthened according to the specific conditions of each period, in order to minimize consumption while ensuring the quality of the process. 5. Strictly adhere to one’s post and avoid doing anything unrelated to the tasks required at that position; do not leave the post without the permission of the team leader. 6. Maintain the cleanliness of equipment and related areas. III. Process Parameters (1) Pressure - Inlet pressure of the first stage: ≤0.34 Mpa - Cooling water pressure: ≥0.15 Mpa - Outlet pressure of the ice maker: ≤1.57 Mpa - The pressure in the oil main pipe is 0.15–0.3 Mpa higher than the exhaust pressure. (2) Temperature - Inlet temperature of the first stage: 10–30℃ - Outlet temperature of the ice maker: ≤105℃ - Oil temperature: ≤65℃ (3) Liquid level - During normal operation of the ice maker, the oil level should be at 1/2 of the height of the sight glass. (IV) Interlock protection signals: Exhaust pressure high protection: 1.57 MPa. High fuel injection temperature protection: 70°C. Low pressure difference between oil pressure and exhaust pressure protection: 0.1 MPa. High pressure difference before and after the oil refined filter protection: 0.05 MPa. Low suction pressure protection: -0.03 MPa. IV. Process Overview: The gaseous ammonia coming from the ammonia synthesis evaporator passes through a separator to remove any liquid droplets, after which it enters the screw chiller. There, it is pressurized and then sent to an oil separator, where the oil carried in the gaseous ammonia is removed. The ammonia is then condensed into liquid ammonia in the ammonia condenser; this liquid ammonia is collected in a tank and either sent to the ammonia evaporator with model number 670 or to the ammonia regenerator with model number 669 for use, or stored in an ammonia storage warehouse. The oil circuit system includes: a high-efficiency oil separator, an oil cooler, a coarse oil filter, an oil pump, a fine oil filter, a pressure balance valve, an return oil filter, etc. Its structure and functions are as follows: (1) Oil separator: Function – to separate the lubricating oil contained in the compressor exhaust, thereby purifying the high-pressure gas refrigerant that enters the condenser, reducing the adverse effect of the lubricating oil film on heat transfer, and lowering the consumption of lubricating oil. At the same time, the necessary oil level difference is established to ensure the proper operation of the oil cooling system. Structure: Horizontal oil separator. The high-pressure gas discharged by the compressor is directed through the exhaust pipe into the oil separation chamber, where it slows down and changes direction, allowing most of the lubricating oil to be separated off; this is the first stage of separation ； As the refrigerant gas flows through the cylinder toward the high-efficiency oil filter element, lubricant particles adhere to the cylinder walls and settle due to gravity, thereby achieving the second stage of separation ； The refrigerant gas enters the high-efficiency oil filter element, where the remaining oil is removed through adsorption and cold aggregation; this represents the third stage of separation. The oil separator is equipped with an electric heater, a safety valve, an oil sight glass, an oil level switch, a vent valve, a return oil valve, and a drain valve. During operation, the manual bypass valve should remain open. (2) Oil cooler: Function: The lubricating oil separated by the oil separator is at a relatively high temperature, and cannot be directly injected into the compressor to serve as a cooling and lubricating agent. The function of the oil cooler is to cool this lubricating oil so that it can be reused in circulation. Structure: Horizontal shell-and-tube heat exchanger, with oil in the shell side and water in the tube side. Due to the effect of the baffle, the oil turns between the tube shell, passing over the heat exchange tubes multiple times in both vertical and horizontal directions. The lubricant flow rate is approximately 0.5–0.8 meters per second. The cooling water enters the oil cooler through the inlet at the bottom of the end cover, and exits it through the outlet at the top. The maximum inlet water temperature should not exceed 32°C, and the heat transfer tubes are made of seamless steel pipes. The oil cooler is equipped with an exhaust port, a drain port, a sludge discharge port, and a balance vent port, each located on it. (3) Oil coarse filter: Function: To remove larger impurity particles from the lubricating oil, thereby ensuring that the oil entering the oil pump is relatively clean. It also reduces the load on the fine oil filter, helping to maintain proper functioning of the oil pump and compressor and preventing wear. Structure: The housing is made of seamless steel tubes, while the filter element consists of a cylindrical structure fabricated from stainless steel wire mesh. The end caps are removable, allowing for the replacement and cleaning of the filter element. (4) Oil fine filter: Function: To further remove small-sized impurity particles from the lubricating oil, thereby ensuring that the lubricating oil entering the compressor is extremely clean. This helps to ensure proper lubrication of the compressor’s bearings, rotors, shaft seals, and other friction points, allowing them to function properly and reducing wear. Structure: Similar to the oil coarse filter, but the stainless steel wire mesh that makes up the filter element is finer. (5) Oil pump: Function: To supply pressurized oil to various lubrication points, lubricate the friction components, and drive the components of the oil pressure control system. Structure: Rotary pump or gear, driven by an integrated motor. Usage: Before the first start-up, ensure that the oil suction pipe is filled with lubricating oil, and check whether the rotation direction of the oil pump is correct; this can be verified by using the jog function. (6) Pressure control valve: Function: Automatically adjusts the discharge pressure of the oil pump, ensuring that the oil pressure is 0.15–0.3 Mpa higher than the discharge pressure of the compressor. When the oil pump’s discharge pressure is too high, this valve automatically increases the flow rate to reduce the pressure ； Conversely, when the oil pump’s discharge pressure is low, this valve will automatically reduce the flow rate to increase the pressure. Structure: The opening and closing of this valve is achieved by the up and down movement of a piston inside the valve. The two sides of the piston are exposed to the inlet oil pressure and the outlet oil pressure respectively; the piston moves under the force of the spring, which allows the flow rate of oil to be adjusted, thereby maintaining the pressure difference across the oil pump. 　 Note: The set value of this valve is adjusted prior to leaving the factory; if it needs to be set again during use, it should be done by a professional.

I work on screw-type refrigerators~

The structure and working principle of the screw compressor in screw-type refrigerators, as published by Wuxi Central Air Conditioning Recycling Network. Author: Engineer Han. Publication date: 2012-11-22 23:02:05. Views: 453. The screw compressor in screw-type refrigerators operates through a pair of spiral-shaped male and female rotors inside the cylinder... www.wxzykd.com/ne...asp?nlt=36