Diagnostic significance and optimization strategies of key operating parameters of chillers

In the daily operation and maintenance of chillers, accurately grasping the changing trends of core thermodynamic parameters is the key to judging the health status of the system and predicting potential failures. This article will provide an in-depth analysis of four key operating indicators - small temperature difference between evaporation/condensation ends, exhaust superheat, refrigerant subcooling and cooling water temperature, and discuss their physical meaning, normal range and abnormal warning mechanism to provide data support and technical guidance for efficient and stable operation of equipment.

1. "Small temperature difference" between evaporator and condenser ends

"Small temperature difference" refers to the absolute difference between the outlet temperature of the secondary refrigerant (such as chilled water or cooling water) on the evaporator or condenser side of the chiller and its corresponding refrigerant saturation temperature. Specifically:

- Small temperature difference of evaporator = chilled water outlet temperature - saturation temperature corresponding to evaporation pressure

- Small temperature difference of condenser = cooling water outlet temperature - saturation temperature corresponding to condensing pressure

This parameter directly reflects the cleanliness and heat transfer efficiency of the heat exchange surface. Under standard working conditions, this value should usually be controlled within 2.5°C, and should remain stable during operation without sudden changes.

When monitoring finds that small temperature differences increase significantly, great attention needs to be paid. Possible causes can be divided into two categories:

1. Internal problems of the unit: such as scaling of heat exchange tubes, corrosion and perforation of copper tubes causing leakage from the water side to the refrigerant side, non-condensable gas mixed in the system, refrigerant leakage, etc.;

2. Water system problems: including insufficient water flow due to reduced water pump performance, clogged filters, pipeline fouling, or biological slime deposition caused by deterioration of water quality.

Therefore, continuous monitoring of small temperature difference trends can be used as an important basis for preventive maintenance. Timely intervention can avoid energy efficiency decline and even equipment damage.

2. Exhaust superheat

Discharge superheat is defined as the difference between the compressor exhaust temperature and the condensing saturation temperature. It is one of the core parameters for evaluating the working status of the compressor. For centrifugal chillers, the normal exhaust superheat is generally maintained at around 7°C, with a reasonable range of 4~10°C.

The value of this value directly affects the energy consumption level of the compressor. The lower the superheat, it means that the compressor exhaust temperature is close to the condensation temperature, the energy is fully utilized, and the overall system energy efficiency is higher; conversely, the higher the superheat means that the compression process generates too much invalid heat and the power consumption increases.

Shanghai KUB Refrigeration Equipment Co., Ltd.

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