The chiller is widely used in various industries, which makes the chiller have a wide variety of faults. The general customer can't prepare to judge the problem. Sometimes, some small problems users can't solve it, which makes it very troublesome to use. To this end, Shanghai Tianfeng Sort out some common problems with the chiller, in order to help everyone better use the chiller.
1. The relationship between the suction temperature and the exhaust temperature is actually that the exhaust temperature of the system is closely related to the intake air temperature. As the inhalation temperature increases, the exhaust gas temperature also rises relatively, and vice versa. By understanding their relationship, they can master and control them well and make the refrigeration system run better.
2. Suction pressure changes The impact of the refrigeration system When the refrigeration system is running, its suction pressure is closely related to the evaporation temperature and the flow rate of its refrigerant. For systems with expansion valves, the suction pressure is related to the degree of opening of the expansion valve, the amount of refrigerant charge, the cooling efficiency of the compressor, and the magnitude of the load. With a capillary system, the suction pressure is related to the condensing pressure, the cooling capacity, the compressor cooling efficiency, and the load. For this purpose, when checking the refrigeration system, a pressure gauge should be installed on the suction pipe. Detecting inspiratory pressure plays an important role in failure analysis.
(1) Factors with low suction pressure The suction pressure is lower than the normal value. The factors are insufficient cooling capacity, small cold load, small expansion valve opening, low condensing pressure (using a capillary system), and poor filter.
(2) Factors with high suction pressure The suction pressure is higher than the normal value, which is caused by excessive refrigerant, large refrigeration load, large expansion valve opening, high condensing pressure (capillary system), and poor compressor efficiency.
3. Effect of Exhaust (Condensation) Pressure Change on Refrigeration System When the refrigeration system is operating, its exhaust pressure corresponds to the condensing temperature, and the condensing temperature is related to the flow rate and temperature of the cooling medium, the refrigerant inflow, and the cooling load. When inspecting the refrigeration system, an exhaust pressure gauge should be installed at the exhaust pipe to detect the exhaust pressure as an analysis of the fault data.
(1) Factors with high exhaust pressure When the exhaust pressure is higher than the normal value, there is generally a small flow rate of the cooling medium or a high temperature of the cooling medium, too much refrigerant charge, large cooling load, and large expansion opening. The above factors will cause the circulation flow of the system to increase, and the condensation heat load will increase accordingly. Since the heat cannot be completely dissipated in time, the condensation temperature rises, and the exhaust gas (condensation) pressure rises. In the case where the flow rate of the cooling medium is low or the temperature of the cooling medium is high, the heat dissipation efficiency of the condenser is lowered to increase the condensation temperature. In the case where the flow rate of the cooling medium is low or the temperature of the cooling medium is high, the heat dissipation efficiency of the condenser is lowered to increase the condensation temperature. The reason for the excessive refrigerant charge is that the excess refrigerant liquid occupies a part of the condenser, which reduces the condensation area and causes the condensation temperature to rise.
(2) The exhaust pressure is lower than the normal value due to the low exhaust pressure. The factors are low compressor efficiency, insufficient refrigerant quantity, small cold load, small opening of the expansion valve, and the filter is not smooth, including the expansion valve filter. The temperature of the cooling medium is low. The above factors will cause the cooling flow of the system to decrease, the condensation load to be small, and the condensation temperature to drop. From the above-mentioned suction pressure and the change of exhaust pressure and exhaust pressure, there is a close relationship between the two. Under normal circumstances, the suction pressure increases and the exhaust pressure rises accordingly; the suction pressure decreases and the exhaust pressure decreases accordingly. The general situation of the exhaust pressure can also be estimated from the change in the intake pressure gauge.
4. The influence of the temperature change of the evaporation unit on the refrigeration system
(1) Appearance temperature of thermal expansion valve (including electronic expansion valve) Under normal conditions, the lower half of the expansion valve body is very cool, and there is dew, and the refrigerant flow is very dull. Under abnormal conditions, first, the valve body is relatively cold, the surface has more dew, and even frost, the refrigerant has a loud sound (gas flow). The reason is that the filter is blocked, or the refrigerant in the power box leaks, and the valve hole is closed.
(2) When the temperature of the capillary is normal, the capillary is cool and dew is formed, and there is a sound of liquid flow. Under abnormal conditions, the surface is very cool and condensation, but the sound of the flow is louder, which is the flow of gas. The reason is that the refrigerant is insufficient. Second, the surface is not cool, condensation is not observed, and the flow sound is not heard. It is a filter blockage or capillary blockage.
(3) The temperature condition of the evaporator is normal. The outer surface of the evaporator is very cold, and the condensation water droplets are continuously dripped. The temperature of the inlet and outlet air is large, usually Δt can be 12~14OC. Abnormal conditions, evaporator surface Not too cold, not much dew, or no condensation, you can hear the sound of the refrigerant flow is very loud, the temperature difference between the inlet and outlet is small. The reason is that the refrigerant amount is insufficient, or the expansion valve opening degree is small.
5. Environmental temperature effect
(1) Ambient temperature requirements for outdoor units According to national standards, air-conditioning units should be in normal operation at ambient temperatures of 35 VAC or less, and can reach the cooling capacity and other indicators on the product nameplate. When the ambient temperature is in the range of 35~43 OC, the air conditioning unit can operate, but the chilled standard cooling capacity cannot be guaranteed. It is already running at full load. This is the condensing temperature, pressure and exhaust temperature are quite high. If the indoor unit heat is large, the electric control protector may operate, cut off the power supply, and stop running. When the outdoor air temperature exceeds 43 OC, the air conditioning unit is in overload operation, which will cause the electric control device to operate, cut off the power supply, and stop running.
(2) Indoor air conditioning temperature requirements The normal indoor constant temperature value should not exceed 30 OC. If the temperature exceeds 30 OC, the air conditioning unit may be operated under overload conditions. The condensing temperature and exhaust temperature of the refrigeration system will increase, which may also cause the electric protector to operate, cut off the power supply, and operate the air conditioning unit. unfavorable.
(3) Heat pump system The same as the single cooling system, whether the heat pump is running normally, mainly check the working condition of the four-way reversing valve. When the reversing valve is reversed, a relatively loud gas flow sound and a shock of the solenoid valve thimble (electromagnetic field absorbing valve core) can be heard. When the solenoid valve does not hear the above two sounds during the commutation process, the electromagnetic The valve may be malfunctioning.
6. Detection of pressure and temperature in refrigeration systems (1) Pressure concept of refrigeration system The refrigeration system can be divided into high and low pressure parts during operation. The high pressure section is from the exhaust port of the compressor to the front of the throttle valve. This section is called the evaporation pressure. The suction port pressure of the compressor is called the suction pressure, and the suction pressure is close to the evaporation pressure. The difference between the two is the flow resistance of the pipeline. Pressure loss is generally limited to below 0.018 MPa. For convenience, both the evaporation pressure and the condensing pressure of the refrigeration system are detected at the suction and exhaust ports of the compressor. That is, it is usually called the suction and exhaust pressure of the compressor. The purpose of detecting the suction and exhaust pressure of the refrigeration system is to obtain the evaporation temperature and the condensation temperature of the refrigeration system, thereby obtaining the operating state of the refrigeration system. (2) Temperature concept in refrigeration system The temperature in the refrigeration system involves a wide range of surfaces, such as evaporation temperature te, suction temperature ts, condensation temperature, exhaust temperature, etc. Determining the operating conditions of the refrigeration system is the evaporation temperature te and the condensation temperature tc.
1) The evaporation temperature te is the temperature at which the liquid refrigerant is boiled and vaporized in the evaporator. For example, the air conditioning unit te. 5~7OC is the best evaporating temperature of the air conditioning unit, that is to say, the design of the air conditioning unit is between 5 and 7 OC. When the air conditioning unit after the maintenance is in debugging, if the te is less than 5~7 OC, The expansion valve should be operated at a high speed to detect the suction pressure of the compressor. The purpose is to understand the evaporating temperature of the unit during operation, and te can not be directly detected, only by detecting the corresponding evaporating pressure to obtain its evaporating temperature (by referring to the refrigerant thermodynamic property table).
2) The condensing temperature tc is the temperature at which the superheated vapor of the refrigerant condenses into a liquid after being released from the heat in the condenser. The condensing temperature cannot be directly detected, but only by detecting the corresponding condensing pressure, and then by referring to the refrigerant thermodynamic property table. The condensing temperature is high and the condensing pressure is relatively increased, and they correspond to each other. The condensing temperature is extremely high, the unit load is heavy, the motor is overloaded, and the operation is unfavorable. The cooling capacity is correspondingly reduced, and the power consumption is increased, and should be avoided as much as possible.
3) Exhaust temperature td refers to the temperature of the exhaust port of the compressor (including the temperature of the exhaust port). The temperature of the exhaust must be measured by a temperature measuring device. Generally, the small machine is not set up. The temporary measurement can be detected by a semiconductor thermometer. But the error is large. The exhaust temperature is affected by the suction temperature and the condensing temperature. The suction temperature or the condensing temperature increases, and the exhaust temperature rises accordingly. Therefore, the intake temperature and the condensing temperature must be controlled to stabilize the exhaust temperature.
4) The suction temperature ts refers to the gas temperature of the suction connection pipe of the compressor. The temperature measurement device is required to detect the suction temperature. Generally, the small unit does not set the temperature measurement device. Generally, the hand touch is used for the inspection and debugging. The inspiratory temperature generally requires control of ts = 15 OC as well. Exceeding this value has a certain effect on the cooling effect.
7. The effect of the temperature change on the refrigeration system of the compression condensing unit The temperature of the unit components has a normal temperature range. Exceeding this range is an abnormal state. The factors that cause these abnormalities may be malfunctions or incorrect adjustments, but they must be analyzed and processed or checked in time. These temperature points are difficult to measure with a thermometer, and generally can only be estimated by hand, and then judged whether it is normal.
(1) Effect of exhaust temperature In the summer, the exhaust temperature of the compressor is relatively high and the hand cannot be touched. According to national standards, the exhaust temperature of the R22 refrigeration system should not exceed 150 OC. Exceeding this temperature line is an abnormal condition. The reason why the exhaust gas temperature is too high is that the suction temperature of the compressor is extremely high, or the condensing temperature is too high, and attention must be paid. Exhaust gas temperature is too low, the hand touches the exhaust pipe is not hot, which indicates that the inhalation temperature is extremely low, the compressor may be wet running or the system working condition is relatively small. The wet stroke of the compressor easily damages the valve structure; the operation of the refrigerant is extremely small, which will affect the heat dissipation of the winding of the motor and accelerate the aging of the insulating material.
(2) The influence of the temperature change of the casing on the compressor and the refrigeration system The temperature field of the outer casing of the fully enclosed reciprocating piston compressor can be divided into two parts: a. The upper casing is affected by the suction vapor, the temperature is relatively low, and it is in the micro The range of heat or slightly cool, estimated to be around 30 OC, there is the possibility of dew condensation on the surface of the local casing around the suction pipe. B. The heat generated by the motor in the lower casing and the frictional heat carried by the frozen oil are mainly taken out of the casing by the steam.
1) Influence of high temperature of the casing and its cause The surface temperature of the casing exceeds the normal range, mainly because the intake temperature of the refrigeration system is too high (above 15 OC). Excessive heat vapor enters the compressor and absorbs heat from the casing, causing the temperature of the vapor to rise higher, thereby raising the temperature of the casing. The temperature of the superheated vapor rises very high, and the temperature of the casing rises too high, which is unfavorable for the cooling of the oil, which affects the lubrication of the moving parts, accelerates the wear, and causes the bearing to hold the shaft (biting). It also causes the exhaust gas temperature to rise.
2) The effect of the case temperature is too low and the cause The surface temperature of the case is lower than the normal range because the intake temperature is too low (less than 15 OC). It is good for cooling both the refrigeration oil and the motor windings, but the cooling capacity is reduced. When the inhalation temperature is extremely low, most of the casing will be dew condensation, and there is a danger of liquid hammer. This is a fatal blow to the compressor and should be paid special attention. At the same time, a large amount of refrigerant is dissolved in the frozen oil, which is not conducive to the lubrication of moving parts.
(3) Temperature condition of the condenser
1) Temperature condition of the condenser Normally, the first half of the heat pipe is very hot, and its temperature has a slow and slow step-down balance. The thermal sensitivity of the rear half of the heat pipe is greatly reduced compared with the first half, because the refrigerant in the second half of the pipe has gradually liquefied, and the condensation temperature and the supercooling temperature have been reached. When an abnormal situation occurs, one is that the first half is not too hot, and the second half is close to normal temperature (ambient temperature) because the compressor sucks the wet steam refrigerant or the refrigerant amount is insufficient. The other is that the entire condenser is very hot due to excessive refrigerant volume or low ventilation, or high ambient temperature.
2) Water-cooled condenser The shell of the shell-and-tube condenser is normally warmer in the upper half and the lower half. Under abnormal conditions, the entire casing is not too hot, because the refrigerant is not enough. In the other case, the entire housing is very hot due to insufficient cooling water or poor heat dissipation (scale in the water pipe). Under normal conditions, the casing condenser is very hot. The reason is that the cooling water is too small or the heat dissipation effect is poor. The other is that the outer surface of the casing is not too hot, because the refrigerant is insufficient.
(4) Temperature condition of the reservoir Under normal conditions, the suction tube feels cool by hand and is exposed to dew. The reason is that the condenser has poor heat dissipation, high condensation temperature or excessive refrigerant charge.
(5) Liquid tube temperature condition Under normal conditions, the liquid tube is warm. Under abnormal conditions, the liquid tube is hot. The reason is that the condenser has poor heat dissipation, high condensation temperature or excessive refrigerant flow.
(6) The basic condition of the filter temperature condition is the same as that of the infusion tube, but it has a prominent abnormal phenomenon, that is, the filter may be cold, because the filter mesh is blocked by the sludge, so that the filter is not smooth, when When the refrigerant flows through the filter, a throttling phenomenon occurs, that is, a part of the liquid vaporizes and absorbs heat, causing the filter to cool and causing serious condensation. Another abnormal phenomenon is that the filter is not hot and is equivalent to the ambient temperature. The reason is that the filter is completely blocked and the refrigerant cannot flow.
(7) Temperature condition of the suction pipe Under normal conditions, the suction pipe feels cool by hand and is exposed to dew. Under abnormal conditions, first, the suction pipe is cold and the dew is too much, so that the casing is exposed to a large area. The reason is that the refrigerant flow rate is too large, the liquid cannot be completely vaporized in the evaporator, and there is a liquid reflux phenomenon. The hazard is that the compressor may run on a wet stroke. In severe cases, a liquid blow will occur and the valve piece will be threatened. Second, the suction pipe is not cool, does not condense, and the casing is very hot. The reason is that the refrigerant flow rate is too small or the refrigerant amount is insufficient. The consequence is that the exhaust gas temperature rises and the cooling capacity decreases.
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