1 commonly used cold dryers divided into several categories? Answer: The common cold dryer is divided into air-cooled type and water-cooled type according to the cooling mode of the condenser; the air type (below 80 °C) and the normal temperature air intake type (about 40 °C) are classified according to the high and low intake air temperature; According to the working pressure, there are common type (0.3-1.0MPa) and medium and high pressure type (1.2MPa or more). In addition, many special specifications of the dryer can be used to deal with non-air media, such as: carbon dioxide, hydrogen, natural gas, blast furnace gas, nitrogen and so on. 2 What are the technical parameters of the cold dryer? Answer: The technical parameters of the dryer mainly include: treatment capacity (Nm3/min), intake air temperature (°C), working pressure (MPa), pressure drop (MPa), compressor power (Kw), cooling water consumption ( t/h). The target parameter of the dryer is “pressure dew point†(°C), which is generally not listed as an independent parameter on the “performance specification sheet†in the catalogue of foreign manufacturers. The reason for this is that the "pressure dew point" is related to many parameters of the compressed air being treated. If the “pressure dew point†is marked, the relevant conditions (such as intake air temperature, working pressure, ambient temperature, etc.) must also be included. 3 What is the factor of the load of the dryer? Answer: The load of the dryer depends on the moisture content of the compressed air being treated. The higher the water content, the higher the load. Therefore, the working load of the dryer is directly related to the flow rate of the compressed air to be treated (Nm3/min). The parameters that have the most influence on the load of the dryer are: 1 intake air temperature: the higher the temperature, the air moisture content The more the dryer, the higher the load; 2 Working pressure: Under the same temperature conditions, the lower the saturated air pressure, the more water content, and the higher the load on the dryer. In addition, the relative humidity of the air compressor in the suction environment is also related to the saturated water content of the compressed air (see Item l-10), so it also affects the load of the dryer: the greater the relative humidity, the water content in the saturated compressed gas. The more the dryer, the higher the load. 4 How is the refrigerant evaporation pressure of the dryer? Answer: Refrigerant evaporation pressure is an important parameter for the normal operation of refrigeration equipment. The evaporation pressure is high, the evaporation temperature is also high, and the compressed air does not reach the required cooling temperature, resulting in a too high dew point. If the evaporation temperature is too low, the refrigeration capacity of the compressor will decrease, which will also affect the dew point of the compressed air, and it will easily cause a "liquid compression" accident. Therefore, the evaporation temperature must be controlled within a reasonable range. The air-cooled type cold-drying machine uses a pressure controller to detect the refrigerant evaporation pressure (or condensing pressure). When the pressure reaches a certain upper limit, the fan is turned on, the condenser is forced to be ventilated and cooled, and the refrigerant low pressure is limited by reducing the high pressure of the refrigerant. When the pressure is lower than a certain lower limit, the fan stops, so that the evaporation pressure of the refrigerant does not drop too low. The water-cooled type dryer controls the amount of cooling water through the opening degree of the automatic water quantity regulating valve to keep the pressure of the refrigerant at a normal value. 5 What kind of refrigerant is used in domestic dry-drying machines? What are the characteristics? A: At present, most of the domestic cold-drying machines use R22 as the refrigerant. Its characteristics are: no burning, no explosion, no color, no smell, little toxicity, is a safe refrigerant; R22 unit volume cooling capacity is nearly 50% larger than R12 and its substitute R134a; between R22 and lubricating oil is micro Soluble. They are mutually soluble in the compressor crankcase and condenser. It is separated again in the evaporator. R22 produces acid in the presence of traces of moisture and slowly corrodes the metal. Therefore, when the refrigerant is poured and the frozen oil is added, it is necessary to waterproof into the system. 6 What are the difficulties in the current promotion of R134a in China? A: In recent years, due to environmental protection needs, some industrialized countries have begun to use R134a as a refrigerant for the dryer. The thermodynamic properties of R134a refrigerant are similar to those of R12 and are a substitute for R12. However, R22 is widely used in the dryer, and its unit volume cooling capacity is about 50% larger than that of R12 (or R134a). If R134a is used instead of R22, the thermal calculation and structural design of the current refrigeration system will be significantly modified. In addition, R134a has a much stricter limit on moisture than R22, especially for the drying of the two devices (evaporator and condenser), the infusion method of refrigerant and refrigeration oil, the on-site production and maintenance environment will be much stricter. Claim. So this replacement cost will be very high. What is the relationship between the cooling capacity of the 7 compressor and the load of the dryer? A: The heat load calculation is the basis for the design of the refrigeration system of the dryer. In the presence of a pre-cooler, we use the evaporator heat load as the basis for selecting the refrigeration compressor and other components of the refrigeration system. Since the operating conditions of the dryer are constantly changing, the evaporator heat load varies with the intake air temperature, gas pressure, and environmental conditions (temperature, humidity, etc.). The determination principles for calculating the heat load of evaporators of different manufacturers are not the same. However, in any case, the cooling capacity of the refrigeration compressor is always greater than the calculated thermal load of the evaporator, otherwise the treatment effect of the compressed air under extreme working conditions cannot be guaranteed. For a selected refrigeration compressor, the cooling capacity is mainly determined by the evaporation temperature and the condensation temperature (calculated by the LgP-i diagram), and has no relationship with the evaporator heat load. This is why the phenomenon of “big marathon†appears in the cold-drying opportunity at low load. 8 How is the condensate of the dryer produced? Answer: After the saturated high-temperature compressed air enters the dryer, the water vapor contained in it is condensed into liquid water by two ways, namely: 1 the water vapor directly contacting the cold surface is the low temperature surface of the pre-cooler and the evaporator ( For example, the outer surface of the heat exchange copper tube, the heat dissipating fins, the baffle plate and the inner surface of the container shell are condensed and dew condensation (as in the natural surface condensation process); 2 the water vapor which is not in direct contact with the cold surface is the air current itself. The solid impurities in the entrainment are condensation condensation of “condensation nodules†(like the formation of clouds and rain in nature). The initial particle size of the condensed water droplets depends on the size of the "condensation nodules". If the particle size distribution of the solid impurities mixed in the compressed air entering the dryer is between 0.1 and 25 μ, the initial particle size of the condensate is at least the same order of magnitude. Moreover, in the process of following the flow of compressed air, the water droplets, the water droplets and the cold surface continuously collide and accumulate, and the particle size thereof will continue to increase, and after being increased to a certain extent, it is separated from the gas by its own weight. Since the solid dust particles carried by compressed air act as "condensation nodules" in the process of condensate formation, this also inspires us to believe that the formation of condensate in the dryer is the "self-cleaning" process of compressed air. 9 How is compressed air and condensate separated? Answer: The formation of condensate and the process of separating steam and water in the dryer are started after the compressed air enters the dryer. This soda separation process becomes more intense after the baffles are placed in the precooler and evaporator. The condensed water droplets accumulate and grow up after the collision with the baffle due to the combined action of motion, inertia and gravity, and finally realize the separation of steam and water under the action of gravity. It can be said that a considerable part of the condensate in the dryer is "spontaneous" for steam-water separation during the flow. In order to capture a portion of the fine water droplets remaining in the air, a more efficient dedicated gas water separator is provided in the dryer to minimize the liquid water entering the exhaust pipe to minimize the "dew point" of the compressed air. 10 What is the significance of discharging condensate in time for the operation of the dryer? Answer: When the dryer is working, a large amount of condensed water will accumulate in the pre-cooler and the evaporator vessel. If the condensate is not discharged in time, the dryer will become a water reservoir. The result: 1 a large amount of liquid water entrained in the exhaust gas, so that the work of the dryer is meaningless; 2 the liquid water in the machine should absorb a large amount of cold, so that the load of the dryer is increased; 3 the flow area of ​​the compressed air is reduced, the air pressure Lower the increase. Therefore, timely and completely discharging the condensed water in the dryer is an important guarantee for the normal operation of the dryer. Why use an automatic drainer in the 11 dryer? A: In order to discharge the condensate from the dryer in time and completely, the easiest way is to open a drain hole at the end of the evaporator to continuously discharge the condensed water generated inside the machine. But its drawbacks are also obvious. Because the compressed air is also continuously discharged while draining, the compressed air pressure drops rapidly. This is not allowed for the gas source system. Manually draining the hand valve is feasible, but it requires a lot of manpower and a series of management troubles. With the automatic drainer, the water in the machine can be automatically eliminated at regular (quantitative). How does the 12 automatic drainer work? Answer: When the water level in the drain water tank does not reach a certain height, the pressure of the compressed air will press the float ball to close the drain hole, so that the airflow will not be leaked; as the water level in the water storage cup rises (in this case, the air dryer) There is no water accumulation. When the float rises to a certain height, the drain hole is opened, and the condensed water in the cup is quickly discharged outside the machine under the action of air pressure. After the condensed water is drained, the float ball closes the drain hole under the action of air pressure. Therefore, the automatic drain is an energy saver. It is not only used in cold dryers, but also widely used in various gas source treatment equipment such as gas tanks, aftercoolers and filters. In addition to the commonly used float-type automatic drains, electronic automatic timing drains are often used. The drainage time of the drains and the time interval between the two drains can be adjusted, and the high pressure can be withstand, and the application is also common. 13 What should I pay attention to when using the automatic drainer? A: The automatic drainer in the dryer is arguably the most troublesome component. The reason is that the condensate discharged from the dryer is not clean water, but a thick liquid mixed with solid impurities (dust, rust, etc.) and oil (so the automatic drain is also called "automatic drainer"), which is extremely Easy to block the drainage holes. For this purpose, a filter screen is installed at the inlet of the automatic drainer. However, if the use time is long, the filter screen will be blocked by oil impurities, and if it is not cleaned in time, the automatic drainer will be disabled. Therefore, it is important to clean the filter in the drain at regular intervals. In addition, the automatic drainer must have a certain pressure to work. For example, the lowest working pressure of the commonly used AD-402 automatic drainer is O.15MPa. If the pressure is too low, air leakage will occur. However, the pressure should not exceed the rated value to prevent the water tank from bursting. When the ambient temperature is below zero, the condensate in the water storage cup should be drained to prevent freezing and freezing. How to determine the number and position of the automatic drainer in the 14 dryer? A: There is a limit to the amount of displacement of the automatic drainer. If the amount of condensate generated by the dryer is greater than the displacement of the automatic drainer at the same time, condensed water will accumulate in the machine. Over time, the condensate will gather more and more. Therefore, in large and medium-sized cold dryers, it is often necessary to install more than two automatic drainers to ensure that no condensed water accumulates inside the machine. The automatic drain should be installed downstream of the pre-cooler and evaporator, most commonly directly below the gas-water separator. 15 What is the impact of the ambient temperature on the operation of the dryer? Answer: The high ambient temperature is very unfavorable for the cooling of the refrigerating machine refrigeration system. When the ambient temperature is higher than the normal refrigerant condensing temperature, the refrigerant condensing pressure is forced to increase, which will reduce the compressor cooling capacity and eventually lead to the "pressure" of the compressed air. The dew point is raised. In general, a lower ambient temperature is beneficial to the operation of the dryer. However, at too low ambient temperatures (eg, below zero degrees Celsius), the compressed air temperature entering the dryer is not low. The compressed air dew point does not change significantly. However, when the condensate is drained outward through the automatic drainer, it is likely to freeze at the drain, which must be prevented. In addition, during shutdown, the condensed water originally accumulated in the evaporator of the dryer or the condensed water accumulated in the water storage cup of the automatic drainer may freeze, and the cooling water stored in the condenser may also freeze, all All of this will cause damage to the components related to the dryer. It should be noted that when the ambient temperature is lower than 2 °C, the compressed air pipeline itself is equivalent to a well-functioning cold dryer. At this time, it is necessary to pay attention to the treatment of the pipeline itself. Therefore, many manufacturers specify in the manual of the dryer that when the temperature is lower than 2 °C, do not use the dryer. 16 What are the requirements for environmental conditions other than temperature? A: The effect of ambient temperature on the operation of the dryer is very large. In addition, the dryer has the following requirements for its surrounding environment: 1 ventilation, especially for air-cooled dryers; 2 dust should not be too much; 3 cold dryers can not have direct radiation at the site Heat source; 4 air should not contain corrosive gases, especially ammonia gas can not be detected. Because ammonia gas has a strong corrosive effect on metallic copper in the presence of water. Therefore, the dryer should not be installed with the ammonia refrigeration equipment. 17 What measures should the cold dryer take when the intake air temperature is too high? Answer: The intake air temperature is an important technical parameter of the dryer. All manufacturers have a clear limit on the upper limit of the intake air temperature of the dryer. Because the intake air temperature is high, it means not only the increase of sensible heat, but also the content of compressed air. The water vapor content has also increased. JB/JQ209010----88 stipulates that the inlet air temperature of the dryer does not exceed 38 °C, and many famous foreign manufacturers of cold dryers have similar regulations. It is reasonable to assume that when the exhaust temperature of the air compressor exceeds 38 °C, a rear cooler must be added downstream of the air compressor to reduce the temperature of the compressed air to a specified value before entering the aftertreatment equipment. The current status of domestic cold-drying machines is that the allowable value of the air-conditioner of the dryer is continuously increased. For example, the ordinary type of dryer with no pre-cooler starts to increase from 40 °C in the early 1990s. At present, the intake air temperature has appeared. It is a normal type dryer with a temperature of 50 °C. Regardless of whether there is commercial speculation, from the technical point of view, the increase in intake air temperature is not only reflected in the increase of gas "temperature", but also reflected in the increase in water content, the increase in the load of the dryer is not simple The linear relationship. If the increase in the power of the refrigeration compressor is used to compensate for the increase in load, it is far from cost-effective because it is most economical to use a rear cooler to reduce the temperature of the compressed air in the normal temperature range. The high-temperature type type dry-drying machine integrates the rear cooler on the cold-drying machine without changing the refrigeration system. The effect is very obvious. 18 can the cold dryer be used to exclude water vapor from other gases? Answer: The cold dryer uses dry water to cool the compressed air. It can of course be used to remove water vapor from other gases. When the cold dryer is used as a non-air type water removal drying equipment, it should have an understanding of the physical and chemical properties of the treated medium and take targeted technical measures. For example, when hydrogen is used for water removal, since hydrogen is an explosive gas, it is necessary to consider explosion-proof measures as a primary condition, such as using an explosion-proof electrical appliance or a split structure. For CO2 water removal, because the aqueous solution of CO2 is slightly acidic, it has corrosive effect on the components of the dryer. Therefore, the parts in contact with the gas should be made of anti-corrosion structure or stainless steel. In addition, it is necessary to understand other physical properties of other gases being treated, such as specific heat, specific gravity, water vapor partial pressure, etc. These parameters have a great influence on the heat load of the cold machine, and thermal calculation must be performed again to make the dryer work. Not overloaded. 19 What should I do if the exhaust temperature of the dryer is very low? A: In some special industries, not only the compressed air with low pressure dew point (ie water content) but also the temperature of compressed air is required, that is, the dryer should be used as a “dehydration coolerâ€. . The measures taken at this time are: 1 cancel the pre-cooler (air-air heat exchanger), so that the compressed air forced to be cooled by the evaporator can not be heated back; 2 simultaneously calculate the refrigeration system, if necessary Increase the power of the compressor, the heat exchange area of ​​the evaporator and the condenser, etc. (a simple method commonly used in practice is to use a larger pre-cooler without pre-cooler to process a smaller flow of gas). How should the 20 cold dryer be properly configured? Answer: The compressed air from the gas source contains a large amount of liquid water, solid dust with different particle sizes, oil and oil vapor. If these impurities are directly entered into the dryer, the operation of the dryer will deteriorate. For example, oil stains can contaminate the heat exchange copper tubes in the pre-cooler and the evaporator, affecting heat exchange; liquid water increases the working load of the dryer, and solid impurities easily block the drain holes. Therefore, it is generally required to install a pre-filter upstream of the air inlet of the dryer for impurity filtration and oil-water separation to avoid the above situation. The pre-filter has a high filtration precision for solid impurities, generally 10--25~, but the separation efficiency of liquid water and oil is higher. Whether the rear filter of the dryer is installed or not should be determined by the user's quality requirements for the compressed air. For the general power gas, a high-precision main line filter can be used. When the gas requirements are higher, the corresponding oil mist filter or activated carbon filter should be configured. 21 What should I pay attention to when using the dryer? Answer: The following matters should be noted when using the dryer: 1 The flow pressure and temperature of the compressed air should be within the allowable range of the nameplate; 2 The installation site should be ventilated, with less dust, sufficient heat dissipation and maintenance space around the machine and can not be installed outdoors. To avoid rain and direct sunlight; 3 cold dryers generally allow no foundation installation, but the ground must be leveled; 4 should be as close as possible to the gas point to avoid too long pipeline; 5 there should be no detectable corrosive gas in the surrounding environment, especially Note that it is not possible to co-locate with the ammonia refrigeration equipment; 6 The filtration accuracy of the pre-filter of the cold-drying machine should be appropriate, and the high-precision is not necessary for the cold-drying machine; 7 The cooling water inlet and outlet pipes should be set independently, especially the outlet pipe can not be combined with Other water-cooling equipment is shared to avoid the drainage caused by the pressure difference; 8 Keep the automatic drainer drained at all times; 9 Do not start the cold-drying machine continuously; 10 The cold-drying machine actually processes the parameters of the compressed air, especially the intake air temperature. When the working pressure does not match the rated value, it should be corrected according to the “correction factor†provided by the sample to avoid overload operation. What should be paid attention to when the 22 cold dryer and the piston air compressor are matched? Answer: The piston air compressor is a non-continuous air supply, and there is a pulse of air flow during operation. The airflow pulse forms a strong and lasting impact on the components of the dryer, which will cause a series of mechanical damage to the dryer. Therefore, when the dryer is used with the piston air compressor, a buffer gas should be set on the downstream side of the air compressor. tank. 23 What are the characteristics of the dryer compared with the adsorption dryer? A: Compared with the adsorption dryer, the freeze dryer has the following characteristics: 1 no gas source consumption, for most gas source users, use cold drying Machine saves energy compared to using adsorption dryer; 2 no valve wear; 3 does not need to add or replace adsorbent regularly; 4 low running noise; 5 routine maintenance is simple, just clean the automatic drain filter on time; 6 pairs There is no special requirement for the pre-treatment of the air source and the supporting air compressor. The general oil-water separator can meet the requirements of the air-drying machine for the intake air quality; 7 the dryer has a “self-cleaning†effect on the exhaust, ie discharge The content of solid impurities in the gas is small; 8 while discharging the condensed water, part of the oil vapor can also be condensed into a liquid oil mist and discharged with the condensed water. Compared with the adsorption dryer, the "pressure dew point" of the cold air dryer for compressed air treatment can only reach about 10 °C, so the drying depth of the gas is far less than that of the adsorption type in the dryer. In a considerable number of applications, it is used for drying. The machine does not meet the requirements of the process for the dryness of the gas source. A selection practice has been developed in the technical world: when the "pressure dew point" is required to be zero, the preferred dryer is used; when the "pressure dew point" is required to be below zero, the adsorption dryer is the only option. What are the characteristics of 24 domestic cold dryers compared with imported cold dryers? A: At present, the domestic cold dryers have little difference in the hardware configuration of parts and components, and the refrigeration compressors, refrigeration parts and refrigerants are used in large quantities. International famous brand. However, the user suitability of the dryer generally exceeds the imported machine. This is because domestic manufacturers have fully considered the characteristics of domestic users when designing and manufacturing the dryer, especially the climatic conditions and daily maintenance features. For example, the domestic refrigeration machine's refrigeration compressor power is generally larger than the imported machine of the same specification, which fully adapts to the characteristics of China's vast territory and large temperature difference between different regions and different seasons. In addition, domestically produced machines are also quite competitive in terms of price, and they have an incomparable advantage in after-sales service. Therefore, domestically produced cold dryers are very popular in the domestic market. At present, the gap between the domestically produced cold-drying machine and the imported cold-drying machine is mainly reflected in the level of the production process, especially in the aspects of pipeline cleaning, assembly welding and the like of the refrigerant system. In addition, the imported machine now has a common use of the environmentally friendly refrigerant R134a, which has no destructive effect on the atmospheric ozone layer, which is difficult to achieve on domestically produced cold dryers. What are the derivatives of 25 dryers? A: Since the 1990s, the dryer has successfully replaced the adsorption dryer in some areas, and has rapidly developed into a non-negligible industrial group. With the need of market competition, there are some derivatives in the country that have been crowned with “X-generation cold dryers†from time to time. Such as: "Cryogenic cold dryer", "combined cold dryer", "cool storage type cold dryer" and so on. As a new product discussion and development, it is not impossible. However, from the perspective of actual effects, these derivatives are subject to various reasons (both technical and market). At present, there is still a lot of work to be done to serialize and commercialize them. More bigger. Many foreign manufacturers with decades of production history and much stronger strength are much more cautious in this respect. At least in their product catalogues, there are currently not many different types of dryers. Product introduction. Freeze dryers and adsorption dryers, due to their maturity, stable performance and price advantage, their position in their respective fields of application seems to be difficult to shake in the near future. 26 How to evaluate the thermal efficiency of the dryer? A: As a kind of heat exchange equipment, the thermal efficiency of the dryer is to attract people's attention. Like all other thermal equipment, the thermal efficiency of a dryer is also defined as: "the ratio of effective energy to supply energy." We know that the purpose of the work of the dryer is not for refrigeration, but refrigeration is only an intermediate means of achieving relatively dry compressed air for repelling moisture. Therefore, its effective energy can only be the amount of cooling (Q effective) consumed to generate condensed water. Others, such as the cooling capacity taken away by the exhaust gas temperature, should be counted as “waste coldâ€. The supply energy of the dryer is the cooling capacity (Q supply) of the refrigeration compressor under the specified operating conditions, which is usually much larger than the calculated thermal load of the evaporator. Formulated to represent thermal efficiency η = Q effective / Q supply. 27 What is the development prospect of the dryer? A: As a post-processing equipment for air compressors, the dryer is only a single auxiliary machine. However, with the advancement of technology, various industrial sectors are increasingly demanding the quality of gas sources, and the market for cold dryers will be larger and larger. It can be said that as long as air compressors are developing, the prospects for dryers will become more and more important. it is good. The development direction of the dryer technology is energy saving and high efficiency, the second is green environmental protection, and the third is the further improvement of the control system. Compared with adsorption dryers, freeze dryers are relatively energy efficient in their field of application. However, when the cold dryer is running at a small load, there is also a waste of energy in the “big horse trolleyâ€. It is hoped that the power consumption of the dryer can be adjusted by following the load change to achieve the best energy saving effect. In this respect, the frequency conversion technology has a good application prospect. In terms of improving heat transfer performance, the use of compact heat exchangers, such as plate-fin heat exchangers, is promising (current difficulties may still be in terms of price). The promotion of the use of environmentally friendly refrigerant R134a is the development direction of all refrigeration equipment including cold dryers, and there are no insurmountable obstacles in technology. But this is a big social project. The individual actions of an industry or a certain company have little practical effect on the overall ambitious goals, except for some commercial propaganda. In the final analysis, this is a government act, and it is necessary for the state to introduce policies to stipulate a unified time limit. As a compressed air post-treatment purification equipment, the control system of the dryer will be continuously improved following the advancement of the host control technology. There are many things to do in terms of frequency control, online dew point measurement and control, real-time display of operating conditions and record keeping. How high is the condensing pressure of the refrigerant in the condenser? Answer: The pressure of the condenser of the refrigeration equipment is of national standard. In normal operation, the condensing pressure of R22 is preferably not more than 1.5 MPa. In practice, for various reasons, the condensing pressure is exceeded. Excessive condensing pressure will bring many disadvantages to the refrigeration system (for the dryer, the most obvious is the rise in dew point). Long-term operation under high condensing pressure will affect the service life of the refrigeration compressor. The dryer is equipped with high pressure protection. 29 What is the cause of excessive condensing pressure? Answer: The reasons for the high pressure of the water condenser are: 1 the cooling water is not enough, the water temperature is too high; 2 the condenser heat transfer area is small; 3 the air is immersed in the refrigerant system (caused by the evaporator copper tube rupture); 4 the condenser housing volume is small The memory refrigerant liquid uses an effective heat transfer area to be reduced or the refrigerant is overcharged; the 5 water condenser is used for a long time. Copper pipe water side surface scale; 6 automatic water volume control valve opening degree is small or damaged; 7 refrigeration oil enters the refrigeration system; 8 cooling water pipe is unreasonable, resulting in poor cooling water return; 9 refrigerant passage or components (dry filter, Solenoid valves, capillaries, etc.) are blocked; 10 cold dryer load is too large. The evaporation pressure is raised and the condensation pressure is raised. The reasons for the high condensing pressure of the air-cooled condenser are: 1 high ambient temperature or poor ventilation; 2 the surface area of ​​the condenser has dust and dirt; 3 the load of the cold dryer is too large; 4 the air invades the refrigerant system; 5 the heat transfer area of ​​the condenser is insufficient; 6 cooling fan air volume is small; 7 cold dry hunger installation location is not correct (such as close to the heat source, the sun is directly exposed, the cold-drying machine is arranged too close to the front and rear, etc.); 8 control fan pressure switch is improperly set or damaged; 9 refrigerant passage or The component has a blockage; 10 the refrigerant is filled too much, so that the heat transfer area is reduced. 30 What is the cause of the condensing pressure too low? Answer: The reasons for the condenser condensing pressure are too low: 1 the cooling water is too much or the water temperature is too low; 2 the ambient temperature is too low; 3 the pressure switch of the control fan or the automatic water regulating valve for controlling the cooling water is improperly set or damaged; The refrigerant charge is too small; 5 the refrigerant pipe or component has a leak point; 6 the cold dryer load is too small. Generally speaking, the condensing pressure is slightly lower, which has no major influence on the operation of the dryer and the refrigeration system. However, if the condensing pressure is too low, the evaporation pressure will decrease, causing frost in the evaporator and even "liquid compression" of the compressor. This is something that needs to be prevented.