[Mechanical Equipment Technology Edition] Daily Question 201807023: Refrigeration Systems—Case Analysis (1)
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This post was last edited by YORK Industrial Refrigeration on 2018-7-30 at 15:09. 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; by doing 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. Case analysis: Chiller – the temperature cannot be reduced during the day, and the outlet temperature of the chilled water is 16 degrees. At night, the temperature of the chilled water can be reduced to 8 degrees. It is known that the exhaust pressure limits the loading: 14.92 BAR (the loading is limited when the exhaust pressure reaches 14.92 BAR). During the day, the intake pressure is 6 bar while the exhaust pressure remains at 14.92 BAR; at night, the intake pressure is 4 bar with the exhaust pressure still at 14.92 BAR. All other parameters are normal. Question 1: Why can’t the temperature drop during the day? Answer: Why can’t the temperature drop during the day? Firstly, the load is high during the day, so the evaporation pressure is high; accordingly, the exhaust pressure is also high (due to the compression ratio). As a result, the evaporation pressure is greater during the day compared to at night, and the capacity of the system is limited under such conditions. The high evaporation pressure and these capacity limitations lead to a higher evaporation saturation temperature. The evaporator exchanges heat with the chilled water based on this saturation temperature, and when the saturation temperature is high, the temperature of the chilled water cannot drop further. ============================== High-quality promotions: Mechanical equipment——Videos on the repair and calibration of York compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment——Maintenance procedures for York screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment——Upgrading of 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 Maekawa MYCOM screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
Isn’t it the case that the load is high during the day and low at night?
Yes, that’s obvious. Could it be analyzed in more detail? ji
The reason may be that the ambient temperature during the day is too high, preventing the cooling water temperature from dropping and resulting in excessive condensation pressure; when this pressure reaches the limit set by the exhaust pressure,； The compressor is limited in its loading, so the equipment operates at partial load; as a result, the temperature of the chilled water does not drop, and it is therefore not possible to reach the desired temperature.
The other parameters are fine; including the cooling water temperature, which is also okay
Based on the known conditions, there are no issues with the other parameters
The load is too high; the pressure is high, so the press has limited the loading. At night, the inlet temperature of the chilled water naturally decreases. So the outlet water temperature is also low.
It doesn’t hit the mark. The water temperature is fine; to be honest, this place uses groundwater, so it’s not affected by day or night temperature changes.
This is a practical-type question; at first I didn’t know where to start. After thinking it over repeatedly and consulting relevant information, it seems that the approach might be as follows: 1. First, based on the given conditions, when the exhaust pressure reaches 14.92 bar, loading is restricted – this is a setting specified by the machine and cannot be changed in the context of this question. 2. Based on the parameters for day and night, despite different inlet pressures, both cases reached an exhaust pressure of 14.92 bar, which limited the loading capacity ； The cooling water temperatures are 16°C and 8°C respectively. 3. Normal values for other parameters indicate that there are no abnormal parameters. Analysis: The machine reaches the 14.92 bar loading limit during the day, which indicates that high temperatures during the day result in a high load on the cooling system. The system gradually increases its load until it reaches this limit; as a result, the temperature of the chilled water can only reach 16°C, indicating that the unit has reached its maximum capacity. If this parameter does not meet the user’s requirements, it indicates that the selected unit system is too small; in other words, the unit needs to be reconfigured by adjusting the constraints within acceptable limits. At night, as the ambient temperature dropped, the cooling load decreased; although it still reached the limit load of 14.92 bar, the temperature of the chilled water fell to 8°C, which met the user’s requirements. I wonder if the teacher’s question is related to this area of study? Please correct me!