- The suction temperature of the Quick Freezing Equipmentis too high-mainly due to the increase in the superheat of the suction. Note that the high suction temperature does not mean that the suction pressure is high, because the suction is superheated steam.
Under normal circumstances, the compressor cylinder head should be half cold and half hot. If the suction temperature is too high, the cylinder head will all heat up. If the intake temperature is higher than normal, the exhaust temperature will increase accordingly.
The reasons for the high suction temperature of quick freezing equipment are:
(1) Insufficient refrigerant charge in the system: Even if the expansion valve is opened to the maximum, there will be no change in the amount of liquid supplied, so that the refrigerant vapor is overheated in the evaporator and the suction temperature increases.
(2) The opening degree of the expansion valve is too small: the system has insufficient circulation of refrigerant, the amount of refrigerant entering the evaporator is small, the degree of superheat is large, and the suction temperature is high.
(3) Expansion valve port filter clogged: the amount of liquid supplied in the evaporator is insufficient, the amount of refrigerant liquid is reduced, and a part of the evaporator is occupied by superheated steam, so the suction temperature increases.
(4) The suction temperature is too high due to other reasons: If the heat insulation of the return air pipeline is not good or the pipeline is too long, it can cause the suction temperature to be too high.
- The suction temperature of the quick-freezing equipment is too low-mainly caused by the low suction superheat caused by the large liquid supply of the evaporator.
(1) The refrigerant charge is too much: it occupies part of the volume in the condenser and increases the condensing pressure, and the liquid entering the evaporator increases accordingly. The liquid in the evaporator cannot be completely vaporized, so that the compressor sucks the gas with liquid droplets. In this way, the temperature of the return air pipe decreases, but the evaporation temperature does not change because the pressure does not decrease, and the degree of superheat decreases. Even if the expansion valve is closed, there is no significant improvement.
(2) The opening degree of the expansion valve is too large: the temperature measured by the temperature sensing element is inaccurate because the temperature sensing element is too loosely bound, the contact area with the return air pipe is small, or the temperature sensing element is not wrapped with thermal insulation material and the position of the wrapping is wrong , Close to the ambient temperature, increasing the opening degree of the expansion valve action, resulting in excessive liquid supply.
One reason: as above.
Reason two: Insufficient refrigerant charge, it will be condensed from the evaporator to the compressor (Note: need to be verified); Reason three: Due to external reasons, the refrigerant in the evaporator is insufficient or does not evaporate. It can even cause wet compression. (If the return air of the central air conditioner is insufficient or the filter of the air conditioner box is seriously blocked, the return air pipe of the compressor of the chiller unit will be frosted and the exhaust temperature is also very low).
- Exhaust gas temperature is abnormal-influencing factors: adiabatic index, compression ratio, suction temperature.
The compressor discharge temperature can be read from a thermometer on the discharge line. It is related to the adiabatic index of the refrigerant, compression ratio (condensing pressure / evaporating pressure) and suction temperature. The higher the intake temperature and the greater the compression ratio, the higher the exhaust temperature, and vice versa.
When the suction pressure is constant, the exhaust temperature rises when the exhaust pressure increases; if the exhaust pressure does not change, the exhaust temperature also increases when the suction pressure decreases. In both cases, the compression ratio is increased. Excessively high condensation temperature and exhaust temperature are detrimental to the operation of the compressor and should be prevented. Excessive exhaust temperature will make the lubricating oil thinner or even char and coking, which will deteriorate the lubrication conditions of the compressor.
The temperature of the exhaust gas is proportional to the compression ratio (condensing pressure / evaporating pressure) and the suction temperature. If the superheat temperature of the intake air is high and the compression ratio is large, the exhaust temperature will also be high. If the suction pressure and temperature do not change, when the exhaust pressure increases, the exhaust temperature also increases.
The main reasons for the increase in exhaust temperature are:
(1) The intake temperature is high, and the exhaust temperature after the refrigerant vapor is compressed is also high.
(2) When the condensing temperature increases, the condensing pressure is also high, causing the exhaust temperature to increase.
(3) The exhaust valve is crushed, the high-pressure steam is repeatedly compressed and the temperature rises, the cylinder and the cylinder head are hot, and the temperature indicator on the exhaust pipe also increases.
The actual factors that affect the exhaust temperature increase are:
(1) If the intercooling efficiency is low, or too much scale in the intercooler affects the heat exchange, the suction temperature of the latter stage must be high, and the exhaust temperature will also increase.
(2) Leakage of the valve and leakage of the piston ring not only affect the exhaust gas temperature increase, but also make the interstage pressure change. As long as the compression ratio is higher than the normal value, the exhaust gas temperature will increase.
(3) In addition, for water-cooled machines, lack of water or insufficient water will increase the exhaust temperature. Condensation pressure is abnormal and discharge pressure is reduced.
- The exhaust pressure is high-mainly caused by the high condensation pressure, not the press itself.
The exhaust pressure generally corresponds to the level of the condensation temperature. Under normal circumstances, the discharge pressure of the compressor is very close to the condensing pressure.
As the condensing pressure increases, the compressor discharge temperature also increases. As the compression ratio of the compressor increases, the air transmission coefficient decreases, thereby reducing the compressor's cooling capacity. Increased power consumption. If the exhaust temperature is too high, it will increase the consumption of compressor lubricating oil, make the oil thinner and affect the lubrication; when the exhaust temperature is close to the flash point of the compressor oil, it will also carbonize part of the lubricating oil and accumulate The exhaust valve port affects the tightness of the valve.
Reducing the temperature of the cooling medium can cause the condensing temperature to drop, and the condensing pressure will also decrease, but this is subject to environmental conditions and is difficult to choose. Increasing the cooling medium flow can reduce the condensation temperature (mostly this method). But the flow of cooling water or air cannot be unilaterally increased, because this will increase the power of the cooling water pump or fan and motor, and should be comprehensively considered.
High exhaust pressure will increase the compression work and reduce the gas transmission coefficient, thereby reducing the cooling efficiency.
The main reasons for this failure:
(1) The flow rate of cooling water (or air) is small and the temperature is high.
(2) The presence of air in the system increases the condensation pressure.
(3) Too much refrigerant charge, the liquid occupies the effective condensation area.
(4) The condenser is out of repair for many years and the dirt on the heat transfer surface is serious, which can also cause the condensation pressure to rise. The presence of scale also has a greater effect on condensing pressure.
- The exhaust pressure is too low-mainly caused by the refrigerant flow in the refrigeration system pipeline is too small or even stopped.
The exhaust pressure is too low. Although the phenomenon is manifested at the high-pressure end, the cause is mostly at the low-pressure end. The reason: ice or dirty clogging of the expansion valve, and clogging of the filter, etc., will inevitably reduce the suction and discharge pressure.
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