[Mechanical Equipment Technology Edition] Daily Question 201806020: Refrigeration Systems — Study of Pressure-Humidity Diagrams of Refrigeration Parameters* (10)
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This post was last edited by YORK Industrial Refrigeration on 2018-6-23 at 09:34. 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; by doing so, your skills will improve!) ) Those who comment on this post will receive 1-3 units of wealth as a reward; those who give accurate answers will receive 10-15 units, with the reward valid for two days. ============================== Refrigeration systems – Pressure-enthalpy diagrams of refrigeration parameters* (10): The diagram below shows the pressure-enthalpy diagram of a refrigeration cycle. Please identify the state of the refrigerant at points 1, 2, 4”, and 5 (for example: Point 1: Gaseous refrigerant from the evaporator to the compressor’s suction inlet). Point 1: Gaseous refrigerant from the evaporator to the compressor’s suction inlet. Point 2: High-pressure gaseous refrigerant at the compressor’s outlet and in the condenser. Point 4”: Liquid refrigerant in a supercooled state before passing through the throttle valve. Point 5: Low-pressure, low-temperature liquid refrigerant at the evaporator’s inlet. ============================== Recommended content: Mechanical equipment – Videos on the repair and calibration 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=
Point 1: Gaseous refrigerant from the evaporator to the compressor’s suction port. Point 2: High-pressure gaseous refrigerant at the compressor outlet and in the condenser. Point 4”: Liquid refrigerant in a supercooled state before the throttle valve. Point 5: Low-pressure, low-temperature liquid refrigerant at the evaporator inlet
1-2 represents the superheating process, with point 2 being the compressor suction point. Point 3 is the compressor discharge point, where the refrigerant is in a superheated state. 3-4 is the cooling process,
Point 1: Gaseous refrigerant from the evaporator to the compressor suction port. Point 2: High-pressure gaseous refrigerant at the compressor outlet condenser. Point 4”: The liquid refrigerant in a subcooled state before the throttle valve. Point 5: Low-pressure, low-temperature liquid refrigerant at the evaporator inlet.
Exhaust superheat = Exhaust temperature – Condensation temperature. Now, let’s consider which of these four values is related to exhaust superheat.
1, 2, 4”, and 5 represent the states of the refrigeration cycle. Point 1 indicates the intersection of the P0 isobaric line and the superheating temperature line; point 2 represents the intersection of an isentropic line drawn through point 1 with the Pk isobaric line; point 4” denotes the intersection of the Pk isobaric line and the subcooling temperature line; point 5 indicates the intersection of an isenthalpic line drawn through point 4 with the P0 isobaric line
Point 1: Gaseous refrigerant from the evaporator to the compressor suction port. Point 2: High-pressure gaseous refrigerant at the compressor outlet condenser. Point 3: The liquid refrigerant in a supercooled state before the throttle valve. Point 4: Low-pressure, low-temperature liquid refrigerant at the evaporator inlet.
From the pressure-enthalpy diagram, the area between point 1” and point 1 represents the superheated phase of the refrigerant gas, and point 1 is related to the suction superheat； The temperature difference between 2 and 3 points should be the exhaust superheat; therefore, point 2 is related to the exhaust superheat. I’m not sure if it’s correct? Please ask the teacher for corrections!