[Mechanical Equipment Technology Edition] Daily Question 201805029: Refrigeration Systems – Refrigeration Parameters (3)
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This post was last edited by YORK Industrial Refrigeration on 2018-6-11 at 10:00. This year’s 【Daily Question】is divided into three categories: screw refrigeration compressors, refrigeration systems, and oil circuit systems, aiming to provide a comprehensive understanding of refrigeration technology. (If you encounter something you don’t know or can’t answer, please actively look up information; as you do so, your skills will improve!) ) All participants in the comments on this post will receive 1-3 wealth points; those who give complete answers will get 10-15 points, with the validity period being two days. ============================== Refrigeration systems — Refrigeration parameters (2): What is the subcooling degree of a refrigeration unit? What’s the use? Subcooling: It refers to the temperature at which the refrigerant condenses into a saturated liquid; it is the value below the saturated temperature resulting from subcooling. Difference between subcooling and not subcooling: With subcooling, the throttling process results in less gas flashing, allowing the refrigerant to evaporate more fully, thereby increasing the cooling capacity. Without subcooling, more gas flashes during the throttling process. ============================== Premium promotions: Mechanical equipment – Videos on the repair and adjustment of York compressors: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment – Procedures for maintaining York screw compressors: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment – Upgrading York Quinton control centers: https://bbs.hcbbs.com/thread-1804837-1-1.html Mechanical equipment – Major repairs of GEA Grasox screw compressors: https://bbs.hcbbs.com/thread-1800467-1-1.html Mechanical equipment – Disassembly and maintenance of British HOWDEN screw compressors: https://bbs.hcbbs.com/thread-1832529-1-1.html Mechanical equipment – Disassembly and maintenance of Japanese MYCOM screw compressors: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
Working as a porter again......Subcooling: the difference between the subcooling temperature of a liquid and the saturated liquid temperature corresponding to its pressure. If there is no subcooling, the liquid in the two-phase refrigerant experiences a slight pressure drop in the \"liquid line,\" and as a result the liquid will \"flash.\" A saturated liquid will inevitably evaporate due to this decrease in pressure. The evaporation of liquid absorbs heat from its surroundings, causing the remaining liquid to cool down and reach its saturation temperature at that pressure. In this way, the two-phase refrigerant moves forward while undergoing flash evaporation and saturation, until it reaches the inlet of the evaporator. By then, the dryness degree of the two-phase refrigerant reaching the evaporator will be much higher than the desired value; with a reduced liquid content, it becomes impossible to meet the evaporation requirements of the evaporator, and as a result, the cooling efficiency decreases.
The difference between the temperature of a supercooled liquid and that of a saturated liquid is called the degree of supercooling. The supercooling degree is generally around 3-5 degrees. Subcooling of the refrigerant liquid is very important in refrigeration systems; in water-cooled condenser cooling water systems, it is necessary to maintain a certain pressure and flow rate. In air conditioners, the air-cooled condenser needs to be well-ventilated to facilitate heat dissipation. To achieve supercooling, some systems also require a supercooler in order to obtain a greater degree of supercooling.
Supercooling: The difference between the supercooled temperature of a liquid and the saturated liquid temperature corresponding to its pressure. If there is no subcooling, the liquid in the two-phase refrigerant experiences a slight pressure drop in the \"liquid line,\" and as a result the liquid will \"flash.\" A saturated liquid will inevitably evaporate due to this decrease in pressure. The evaporation of liquid absorbs heat from its surroundings, causing the remaining liquid to cool down and reach its saturation temperature at that pressure. In this way, the two-phase refrigerant moves forward while undergoing flash evaporation and saturation, until it reaches the inlet of the evaporator. By then, the dryness degree of the two-phase refrigerant reaching the evaporator will be much higher than the desired value; with a reduced liquid content, it becomes impossible to meet the evaporation requirements of the evaporator, and as a result, the cooling efficiency decreases.
If heat continues to be removed from the saturated liquid (absorbed by cooling water or air), its temperature will drop further; if the temperature falls below the saturation temperature at the condensation pressure, such a liquid is called a supercooled liquid. Subcooling of the refrigerant liquid is very important in refrigeration systems; in water-cooled condenser cooling water systems, it is necessary to maintain a certain pressure and flow rate. In air conditioners, the air-cooled condenser needs to be well-ventilated to facilitate heat dissipation. To achieve supercooling, some systems also require a supercooler in order to obtain a greater degree of supercooling.
When the refrigerant vapor is condensed into a liquid in the condenser, this liquid is called saturated liquid. If heat continues to be removed from the saturated liquid (absorbed by cooling water or air), its temperature will drop further; if the temperature falls below the saturation temperature at the condensation pressure, such a liquid is called a supercooled liquid. The difference between the temperature of a supercooled liquid and that of a saturated liquid is known as the degree of supercooling, which is generally around 3-5 degrees. Subcooling of the refrigerant liquid is very important in refrigeration systems; in water-cooled condenser cooling water systems, it is necessary to maintain a certain pressure and flow rate. In air conditioners, the air-cooled condenser needs to be well-ventilated to facilitate heat dissipation. To achieve supercooling, some systems also require a supercooler in order to obtain a greater degree of supercooling.
Subcooling is the difference between the temperature at the outlet of the condenser and the temperature corresponding to the condensation pressure; a certain degree of subcooling in the refrigerant prevents flashing of the liquid refrigerant before throttling.
1. Definition: A liquid whose temperature is below the saturation temperature under a certain pressure is called a supercooled liquid. The difference between the temperature of this supercooled liquid and the saturation temperature at the same pressure is known as the degree of supercooling. 2. Purpose: Subcooling is used to reduce the amount of flash gas generated during throttling in the refrigerant liquid before throttling, to decrease the specific volume occupied by this flash gas, and thereby increase the cooling capacity per unit volume ； It also increases the superheat of the return gas, which is beneficial in preventing the compressor from operating under wet stroke conditions. In larger refrigeration systems, in order to lower the temperature of the liquid refrigerant entering the throttle valve, reduce the amount of flash gas generated during or after throttling, and thereby improve the efficiency of refrigeration, a special device for subcooling – a subcooler – is installed in the design after the liquid receiver (a liquid receiver is necessary in systems that use a throttle valve for throttling). Its structural types include sleeve type and spray type, etc. The principle involves using cooling water with a temperature lower than that of the saturated liquid after condensation – such as deep well water – to cool it further; this usually results in a temperature reduction of 3 to 5 degrees compared to before cooling (i.e., a supercooling degree of 3 to 5 degrees). There are also some small fluorine-based refrigeration systems, such as small cold storage units. Although they do not have dedicated subcoolers, the supply pipe and return pipe are wrapped together to insulate them; the low temperature of the return pipe is used to lower the temperature of the liquid in the supply pipe. It is also possible to install a section of the supply pipe and the expansion valve directly inside the storage area, where further cooling is applied to achieve subcooling, thereby improving the efficiency of refrigeration. It also raises the temperature of the return air pipe, preventing the compressor from drawing in overly moist steam that could cause liquid slugging. In systems with capillary throttling, the capillary tube and the return air tube (intake tube) are combined together; some are welded together, others are covered with heat-shrink tubing, some pass through the return air tube, some are wound around it, and still others have the capillary tube or supply tube running directly inside the cabinet. Heat exchange takes place between the capillary tube and the return pipe, allowing the liquid refrigerant prior to throttling to exchange heat with the low-temperature refrigerant vapor in the return pipe, thereby cooling it and achieving supercooling. This not only helps to prevent liquid from being carried in the return pipe and causing damage to the compressor, but also achieves the goal of supercooling the liquid refrigerant before throttling. It is also feasible to deliberately increase the size of the condenser to create space for further cooling and supercooling. But this is not done in a standardized design; the focus is on minimizing the overall volume and weight in order to reduce manufacturing costs. For systems with small or micro capillary throttling, no dedicated subcooler is installed.
A liquid whose temperature is below the saturation temperature under certain pressure is called a supercooled liquid. The difference between the temperature of such a supercooled liquid and the saturation temperature at the same pressure is known as the degree of supercooling. If there is no subcooling, the liquid in the two-phase refrigerant experiences a slight pressure drop in the \"liquid line,\" and as a result, the liquid will \"flash\" – that is, the saturated liquid will evaporate due to the decrease in pressure. As the liquid evaporates, it absorbs heat from its surroundings, causing the remaining liquid to cool down and reach its saturation temperature at that pressure. In this way, the two-phase refrigerant moves forward while flashing and saturating, until it reaches the inlet of the evaporator. The dryness of the two-phase refrigerant that reaches the evaporator in the end will be much higher than the designed value; as a result, the liquid fraction decreases, and it becomes impossible to meet the evaporation requirements of the evaporator, which naturally leads to a reduced cooling effect.
What type is the flow switch for the water circuit in York refrigerators? What should be checked in case of an open circuit fault?
If traffic is detected and it’s an open circuit, that indicates a failure; you can come to me.