5 thông số để dễ dàng đánh giá hệ thống lạnh và điều hòa có chạy bình thường hay không!
1. Condensing temperature
Condensing pressure is the pressure at which refrigerant gas condenses into liquid in the condenser. Since the pressure inside the condenser in the refrigeration system cannot be measured, in fact, the pressure drop of the refrigerant in the exhaust pipe and the condenser is actually very small. Therefore, regardless of design debugging or maintenance, it is generally believed that the exhaust pressure is approximately equal to the condensing pressure.
The condensing temperature and the condensing pressure correspond one-to-one, that is, the saturation temperature during condensation. The condensing temperature is not equal to the temperature of the cooling medium, and there is also a heat transfer temperature difference between the two.
So, how is the condensing temperature determined?
According to experience, the condensing temperature of the system = ambient temperature plus (1015 degree ); we take an air conditioner with an ambient temperature of 35 degree in summer as an example.
In summer, the outdoor ambient temperature of the air conditioner is about 35 degrees, and we can estimate the condensation temperature at this time: condensation temperature = 35 plus (1015 degree C) = 45 degree C.
The pressure corresponding to the condensing temperature is the condensing pressure, (you can check it through the temperature and pressure gauge provided by the Refrigeration Encyclopedia public account). If the exhaust pressure of the refrigeration system is lower than this pressure, please consider whether the refrigerant charge is too small, etc.;
If the exhaust pressure of the system is higher than this pressure, please consider whether the refrigerant charge is too large, whether the heat exchange of the condenser is sufficient, whether the opening of the expansion valve is too small, etc.
2. Evaporation temperature
The evaporation temperature is the temperature at which the liquid refrigerant boils. When the refrigerant flow rate is constant, the lower the evaporating pressure, the lower the evaporating temperature. However, if the evaporating temperature of the system is continuously lowered, the cooling capacity of the refrigeration compressor will also continue to decrease, and the cooling speed may not necessarily become faster, and the lower the evaporating temperature, the lower the cooling coefficient of the system. .
So, how to judge whether the evaporation pressure of the system is normal?
According to experience, the evaporation temperature of the air conditioning system = ambient temperature - (1015 degree C); we take the summer (set temperature in the room 22 degree C) air conditioner as an example:
The temperature of the indoor unit of the air conditioner in summer is 22 degrees, and we can estimate the evaporation temperature at this time: evaporation temperature = ambient temperature - (1015 degree ); that is, evaporation temperature = 22 - (1015 degree ) ≈ 12 degree ;
The pressure corresponding to the evaporating temperature is the evaporating pressure, (you can check it through the temperature and pressure gauge provided by the Refrigeration Encyclopedia public account). If the evaporating pressure of the refrigeration system is lower than this pressure, please consider whether there is a problem with the heat exchange of the evaporator, and the expansion valve is open. Whether the degree is too low.
If the evaporating pressure of the system is higher than this pressure, please consider whether the refrigerant charge is too large, whether the expansion valve opening is too large, and so on.
3. Inhalation temperature
Suction temperature refers to the refrigerant temperature at the compressor suction valve or at the compression buckle. In order to ensure the safe operation of the compressor and prevent the phenomenon of hydraulic shock to the cylinder, the suction temperature is required to be slightly higher than the evaporation temperature, that is, the refrigerant vapor becomes a superheated gas.
Whether the suction temperature is normal can directly feedback whether the opening of the expansion valve is appropriate. Many people know the suction superheat, and also know that the best suction superheat is 57 degree ;
But many novices do not know the actual meaning of this parameter; knowing the suction superheat, we can calculate the normal suction temperature of the system.
Suction temperature = suction superheat plus evaporation temperature, such as:
We know that the evaporation temperature of a refrigeration system is 12 degree ; according to the best suction superheat degree is 57 degree ; we can calculate that the optimal suction temperature of the system at this time is about 17 degree ;
We can judge whether the inhalation temperature is normal at this time according to the feel temperature. For example, if the suction pipe feels colder than 17 degree , we can judge that the opening of the expansion valve is larger or the refrigerant charge is too much; if the suction temperature is hotter than 17 degree , we can judge that the expansion valve is at this time. The opening is smaller or the refrigerant charge is smaller.
If the suction pipe does not condense, it means that the suction temperature is too high, please check whether the refrigerant charge is too small or the opening of the expansion valve is too small. If the suction pipe is frosted (frozen), it means that the suction temperature is low. Please check whether the refrigerant charge is too much or the opening of the expansion valve is large.
4. Exhaust temperature
The exhaust temperature is the temperature of the exhaust gas after the compressor works, which can be measured from the exhaust pipe with a thermometer. The discharge temperature is proportional to the pressure ratio and the suction temperature. The higher the pressure ratio, the higher the suction temperature and the higher the exhaust temperature
Many colleagues have not heard the concept of "exhaust superheat", "exhaust superheat": the difference between the exhaust pipe of the compressor (or the inlet temperature of the condenser) and the saturation temperature corresponding to the condensing pressure.
A normal refrigeration system exhaust superheat is 2030 degree . Therefore, we can judge whether the exhaust temperature is normal based on this empirical value; for example, for an air conditioner with a condensing temperature of 45 degree , the normal value of the exhaust temperature at this time should be:
Exhaust temperature = exhaust superheat plus condensation temperature = 25 plus 45 = 70 degree ;
5. Running current
There are many factors affecting the operating current of the compressor, such as:
Poor heat dissipation of the external machine;
Abnormal external power supply voltage;
The refrigeration system has air;
Poor oil return, resulting in high shell/internal temperature;
Impurities in the system, too much moisture,
In addition, let's talk about the effect of refrigerant and compression ratio on current:
How much refrigerant is compressed
Degree of refrigerant compression (compression ratio)
In fact, it is easy to understand, for the first one: the more refrigerant the compressor compresses, the harder it is for the compressor to compress, and the greater the current. For the second one: the higher the degree of refrigerant compression (the greater the compression ratio), the more work the compressor does, and the corresponding current is greater.
Therefore, the operating current of the compressor can largely reflect whether the refrigeration charge of the refrigeration system is normal. Generally, there is a current value on the nameplate of the refrigeration equipment.
