【Mechanical Equipment Technology Edition】Daily Question 20180709: Refrigeration Systems — Refrigeration Parameters (18)
Thread Content
This post was last edited by YORK Industrial Refrigeration on 2018-7-13 at 08:55. This year’s 【Daily Question】is divided into three categories: screw refrigeration compressors, refrigeration systems, and oil circuits, 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 system – refrigeration parameters (18): The small temperature difference in the condenser = condensation temperature – outlet temperature of the cooling water. The condensation temperature is the temperature of the refrigerant in the shell side. In this process, the high-pressure refrigerant gas T1 coming from the compressor is cooled by the inlet water at temperature L1 to become saturated refrigerant liquid T2; meanwhile, the temperature of the water after heat exchange with the refrigerant is L2. Before heat exchange: T1 exchanges heat with L1. After heat exchange: T1’s temperature drops to T2, while L1’s temperature rises to L2. Anonimously, someone asked: Can the temperature of the cooled water be higher than the saturation temperature of the refrigerant? Why? https://attach01.hcbbs.com/forum/201807/07/082315u5683ar8fyb0h2po.jpg ============================== High-quality promotions: Industrial equipment——Videos on the repair and calibration of York compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Industrial equipment——Process for maintaining York screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Industrial equipment——Upgrading of York Quinton control centers https://bbs.hcbbs.com/thread-1804837-1-1.html Industrial equipment——Major repairs of GEA Grasox screw compressors https://bbs.hcbbs.com/thread-1800467-1-1.html Industrial equipment——Disassembly and maintenance of British HOWDEN screw compressors https://bbs.hcbbs.com/thread-1832529-1-1.html Industrial equipment——Disassembly and maintenance of Japanese MYCOM screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
Can the outlet temperature of the cooling water be higher than the saturation temperature of the refrigerant? Why? 1. By definition: The condensation temperature refers to the saturation temperature at which the refrigerant vapor in the condenser condenses under a certain pressure. A condenser is a device used to convert refrigerant from a gaseous state to a liquid state. If the temperature of the cooling water exiting the system is higher than the saturation temperature of the refrigerant, wouldn’t that end up heating the refrigerant? In this case, it is absolutely impossible to achieve the purpose of condensing the refrigerant. 2. From a heat transfer perspective: In a condenser, the cooling water flows through the tube side, while the refrigerant flows through the shell side; the heat from the refrigerant is continuously transferred to the cooling water. However, according to the basic principles of heat transfer, in an ideal scenario (theoretically only), the temperatures of the two fluids can become equal. Yet, the temperature of the cooling water can never be higher than the condensation temperature of the refrigerant, otherwise the cooling water would end up heating the refrigerant instead. In other words, the condensation temperature is not equal to the temperature of the cooling medium; there is definitely a heat transfer temperature difference between the two. Conversely, it is impossible for the temperature of the cooling medium to be higher than the condensation temperature. .
The outlet temperature of the cooling water must not be higher than the saturation temperature of the refrigerant. Due to the temperature difference in heat transfer, the temperature of the substance being cooled is higher than the evaporation temperature ； The condensation temperature is higher than the temperature of the coolant in the condenser. The saturation temperature of the refrigerant at intermediate pressure (P2) in the intercooler is called the intermediate temperature. The condensation temperature refers to the saturation temperature inside the condenser, and it is generally 2–3 degrees higher than the outlet temperature of the cooling water.
If the temperature of the cooled water at the outlet is higher than the saturation temperature of the refrigerant, it is not possible to achieve the purpose of condensing the refrigerant in such a case. In other words, the condensation temperature cannot be equal to the temperature of the cooling medium; there must be a temperature difference for heat transfer to occur. Conversely, if the temperature of the cooling medium is higher than the condensation temperature, then no cooling effect will take place.
The outlet temperature of the cooling water must not be higher than the saturation temperature of the refrigerant. Due to the temperature difference in heat transfer, the temperature of the substance being cooled is higher than the evaporation temperature ； The condensation temperature is higher than the temperature of the coolant in the condenser. The saturation temperature of the refrigerant at intermediate pressure (P2) in the intercooler is called the intermediate temperature. The condensation temperature refers to the saturated temperature inside the condenser, and it is generally 2–3 degrees higher than the outlet temperature of the cooling water
The outlet temperature of the circulating water will not be higher than the saturation temperature of the refrigerant. When the flow rate of the circulating water is insufficient or the flow rate of the refrigerant is too high, resulting in inadequate heat exchange by the refrigerant, the outlet temperature of the circulating water rises. This in turn causes the outlet temperature of the saturated refrigerant to increase, as well as the saturated vapor pressure. At the same time, the saturation temperature of the liquid refrigerant at the outlet also increases, reaching an equilibrium with the outlet temperature of the circulating water. The ultimate result is a decrease in the flow rate of the saturated refrigerant, while the outlet temperature is the same as or even higher than the water temperature in the cycle.