Flexible circuits, also known globally as flex circuits, flexible printed circuit boards, flex print, or flexi-circuits, are part of the electronic and interconnection family. They consist of a thin insulating polymer film with conductive circuit patterns affixed to it, usually coated with a thin polymer for protection.In view of the actual needs of society, PCB manufacturing in China We need to change some original problems to better serve the society and benefit people. https://www.wellcircuits.com/

　　The technology has been used for interconnecting electronic devices since the 1950s and is now a crucial interconnection technology in many advanced electronic products today.

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　　Size and Weight Reduction Benefits of Flexible Circuitry

　　Wiring solutions that fit where rigid boards cannot.

　　Thin, lightweight products that are durable.

　　Miniaturized versions of existing technologies.

　　Three-dimensional packaging geometry.

　　A low number of device interconnects.

　　Shock and vibration resistance.

　　These benefits highlight flexible circuitry as an ideal solution for mobile consumer electronics. Inside modern devices like smartphones and laptops, flexible circuitry plays a critical role.

　　In mobile devices, using rigid circuitry would result in devices that are too large, heavy, and fragile to carry conveniently, exemplified by the Osborne I, the first fully powered mobile computer, weighing an intimidating 24.5 pounds. Size and weight reduction is only part of the flexible circuit story; they are also ideal for high-temperature and high-density applications.

　　High Temperature and High-Density Applications

　　Flex circuits, often made of polyimide or similar polymers, dissipate heat better than most rigid circuit board materials. This feature allows flexible circuits to be placed in locations where heat would impact the performance of rigid circuit boards.

　　Flexible circuit boards can withstand extreme temperatures ranging from -200＜C to 400＜C, making them desirable for borehole measurements in the oil and gas industry and preferred in industrial sensor technologies for their small size and durability.

　　High temperature resistance, combined with chemical resistance, excellent resistance to radiation and UV exposure, and the ability to control impedances in high-density designs, makes flexible circuits highly beneficial for manufacturers.

　　Why Not Make All Circuit Boards Flexible?

　　Flexible circuit boards are certainly useful, but they are not going to replace rigid circuit boards for all applications. Cost efficiency is the main obstacle to implementing an exclusively flexible circuit board design in a consumer product. Rigid circuit boards are less expensive to manufacture and install in a typical automated high-volume fabricating facility.

　　Typically, the ideal solution for an innovative product is one that incorporates flexible circuitry when necessary, and employs solid, reliable rigid circuit boards where possible to keep manufacturing and assembly costs down.

　　Among all metal core PCBs, aluminum PCBs are the most common type. The base material consists of an aluminum core with standard FR4. It features a thermal clad layer that dissipates heat efficiently, cooling components and enhancing the overall performance of the products. Currently, aluminum-backed PCBs are considered the solution for high-power and tight tolerance applications.In combination with these conditions, PCB manufacturing in China It can still let us see good development and bring fresh vitality to the whole market. https://www.wellcircuits.com/

　　aluminum PCB

　　Advantages of Aluminum PCB

　　Environmentally Friendly: Aluminum is non-toxic and recyclable. Manufacturing with aluminum also conserves energy due to its ease of assembly. For PCB suppliers, using this metal helps maintain the health of our planet.

　　Heat Dissipation: High temperatures can severely damage electronics, so using a material that can dissipate heat is essential. Aluminum transfers heat away from vital components, minimizing potential damage to the circuit board.

　　Higher Durability: Aluminum provides greater strength and durability than ceramic or fiberglass bases. It reduces the risk of breakage during manufacturing, handling, and everyday use.

　　Lightweight: Despite its strength, aluminum is a surprisingly lightweight metal. It adds durability and resilience without increasing the weight of the product.

　　Applications of Aluminum PCB

　　Audio Devices: Input/output amplifiers, balanced amplifiers, audio amplifiers, pre-amplifiers, and power amplifiers.

　　Power Supply: Switching regulators, DC/AC converters, and SW regulators.

　　Communication Electronics: High-frequency amplifiers, filtering appliances, and transmitter circuits.

　　Office Automation Equipment: Motor drives, etc.

　　Automobile: Electronic regulators, ignition systems, power supply controllers, etc.

　　Computers: CPU boards, floppy disk drives, power supply devices, etc.

　　Power Modules: Inverters, solid-state relays, rectifier bridges.

　　Lamps and Lighting: With the growing promotion of energy-saving lamps, various energy-efficient LED lights are well-received in the market, and aluminum PCBs are increasingly used in LED lighting applications.

　　aluminum PCB application

　　If you have any questions regarding PCB and PCBA, please feel free to contact me at

　　Improper use of air conditioningThrough bit by bit efforts, let Puremind Marine Air Conditioners Our market share is getting higher and higher, and the return on investment is also rising steadily. https://puremind.com/

　　Not only will it increase electricity consumption,

　　It may even affect your health.

　　Today, follow the Shanghai Health Promotion Center.

　　Let’s learn the “cold knowledge” of air conditioning use ~

　　Don’t “open and close for a while”

　　I wonder if you have had such an experience?

　　Caught in the strange circle of air conditioning turning on cold and turning off hot, repeated operation is always “cutting suitable”; Or go out and get a courier, thinking that it is more energy-saving to turn off the air conditioner first.

　　In fact, often this behavior of frequently starting the air conditioner increases the power consumption and is not conducive to the maintenance of the air conditioner.

　　Studies have proved that air conditioning “turns on and off for a while” does not actually save electricity. Therefore, if you only go out for a short time, you don’t have to turn off the air conditioner and turn it on again.

　　Pay attention to “humidity” and “temperature”

　　The muggy air has a high humidity, so it is uncomfortable to adjust the temperature. At this time, try to turn on the “dehumidification mode” after air conditioning refrigeration, and the air will become more refreshing and comfortable.

　　If you need to stay in an air-conditioned room for a long time, remember to drink water properly to avoid the loss of water.

　　Practice has proved that it is most appropriate to control the indoor and outdoor temperature difference at 6-8≧, mainly to reduce the burden on the thermoregulation center and avoid the symptoms of dizziness, headache and dry skin and mucosa. Therefore, the air conditioning temperature is set at 26 to 28≧.

　　Don’t sweat and rush into the air-conditioned room.

　　In hot summer, it is easy to sweat when you move a little and bask in the sun. Do you just want to rush into the air-conditioned room? At this time, you should be careful that the disease will come to you.

　　For the general population, sudden cold and heat are easy to catch a cold, have a fever and have diarrhea; It is even more dangerous for patients with hypertension and coronary heart disease.

　　The cardiovascular system in the original thermal environment is in a state of relaxation, and the sudden cooling air after entering the air-conditioned room makes the blood vessels contract urgently, which is prone to dangerous situations such as myocardial infarction.

　　Therefore, don’t rush into the air-conditioned room after sweating, let the sweat collect first, or wipe your body with a dry towel first. When the air conditioner is just turned on, it should not be adjusted to a too low temperature, and at the same time, it should avoid cold air blowing directly on the head, neck and waist and abdomen.

　　Do a good job cleaning

　　The cleaning problem of air conditioning is often easily overlooked, and the bacteria hidden in it will take advantage of the opportunity to cause “air conditioning disease.”

　　Legionella, which lurks in the daily artificial water environment, is such a pathogen. Water contaminated by bacteria can be inhaled by human body in the form of aerosol. After people are infected with Legionella, there will be symptoms similar to pneumonia, such as high fever, chills, fatigue, muscle pain, etc., which may even be life-threatening.

　　The air conditioning system is the main “hiding point” of Legionella, so it is necessary to clean and disinfect the air conditioning; If it is a central air conditioner, the deposited cooling tower water should be replaced and the attached “dirty things” should be removed in time. Don’t forget to clean the casing and filter screen after the “air conditioning season”.

　　In addition, it is recommended to open the window for ventilation every 2-3 hours to ensure the cleanliness of indoor air.

　　What is a fixed-frequency air conditioner? The grid voltage in China is 220 volts and 50 hertz, and the air conditioner working under this condition is called a fixed-frequency air conditioner. Because the power supply frequency can’t be changed, the rotating speed of the compressor of the traditional fixed frequency air conditioner is basically unchanged, and the indoor temperature can be adjusted by constantly “turning on and off” the compressor, which is easy to cause the room temperature to be hot and cold and consume more electricity.more importantly, split system air conditioning and heating Made a fighter in the product, not afraid of any competitor’s attack. https://puremind.com/product-category/puremind-air-conditioner/split-air-conditioner/

　　What is a variable frequency air conditioner? The main engine of the variable frequency air conditioner automatically performs stepless speed change, and it can automatically provide the required cooling (heating) amount according to the room conditions. When the indoor temperature reaches the expected value, the air conditioning main engine will run at a constant speed that can accurately maintain this temperature, so as to realize “non-stop operation”, thus ensuring the stability of the environmental temperature.

　　Advantages and disadvantages analysis:

　　Advantages of fixed frequency air conditioning: affordable price, more options, rich products and various types.

　　Disadvantages of fixed frequency air conditioning: Relative temperature control and energy saving are still slightly inferior to frequency conversion.

　　Advantages of inverter air conditioner: more accurate temperature control, low temperature, wide voltage start, and more energy saving.

　　Disadvantages of inverter air conditioner: the relative price positioning is higher, while the affordable inverter is less optional.

　　To sum up, it is obvious that inverter air conditioners are smarter! But the price will naturally be more expensive.

　　Whether in cold winter or hot summer, air conditioning is an essential household appliance in our home, especially now that people’s living standards have improved, air conditioning has entered thousands of households. Many owners think that choosing air conditioning is the most important thing. I don’t know if it is familiar, but the placement of air conditioning is even more difficult. If it is not in the right position, it will bring trouble to our lives. Many people don’t know the secret of air conditioning placement. Come and have a look with Xiaobian.In some cases, Marine Air Conditioner 220V The advantages will become more and more obvious, and it will be able to develop indomitable after market tests. https://puremind.com/product-category/puremind-air-conditioner/marine-air-conditioner/

　　Where is the most correct place for air conditioning? Many people don’t know the secret of air conditioning ~!

　　Where are the air conditioners placed?

　　(1) How to place the air conditioner in the living room?

　　1. Air-conditioning is a kind of fast-running electrical appliance, so it will transfer the air flow from the outside to the home, such as the main disease in the southwest. Therefore, if the air-conditioning at home is placed in this position, it will definitely make the family suffer from illness and illness this year. Correction method: use a small fan to change the wind direction opposite the air conditioner. In addition, if you want to strengthen the above fortune, you can also move the air conditioner to this position, which has a strong effect on luck and transshipment.

　　2. The most taboo of the air conditioner outlet is to blow to the financial position, and take away the wealth at home together with the cold wind, and the door at home is the main wealth. Therefore, if the air conditioner directly faces the door, it will not only drain the wealth, but also symbolize the popularity. It means that the home is not warm. Correction method: hang a glass screen or cloth curtain at the entrance to solve it.

　　3. The air outlet of the air conditioner directly blows the main chair in the living room (that is, the sofa where three people sit), so that the face sitting here is blown very uncomfortable, which means that the backer is unstable and affects the work and career fortune. Correction: Let the air outlet of the air conditioner come from the side, or move the position of the main sofa.

　　Where is the most correct place for air conditioning? Many people don’t know the secret of air conditioning ~!

　　(2) How to place the air conditioner in the bedroom?

　　1. Air-conditioning often emits a certain amount of heat during refrigeration, so it must be installed far away from other electrical appliances and avoid being installed in corners, which can make the air-conditioning dissipate heat as soon as possible, ensure that it is not damaged, and prolong its service life.

　　2. The air conditioner is installed at a certain distance from the bed. If it is facing the bed or too close to the bed, it will easily lead to the user catching a cold or catching a cold, which will adversely affect people’s health. Therefore, everyone needs to pay special attention to this when installing the air conditioner.

　　Where is the most correct place for air conditioning? Many people don’t know the secret of air conditioning ~!

　　3. Air conditioning is installed in the bedroom in the northeast direction, because the radiation in this direction will be relatively small, so that the harm to the human body can be reduced to. In real life, many owners will ignore this problem, which is actually a very serious misunderstanding.

　　4. The height of the air conditioner installed in the bedroom is very elegant. It is not appropriate to be too high or too low. It is recommended that it be higher than one meter and lower than two meters. This height is the most suitable, and its use effect will be in a new state, and it is more convenient for daily use.

　　Where is the most correct place for air conditioning? Many people don’t know the secret of air conditioning ~!

　　What are the precautions for air conditioning placement?

　　1, kitchen air conditioning moving stove fire

　　It is the place where the whole family can fill their stomachs without installing a kitchen stove. If the air conditioner directly touches the stove fire, it will make the stove fire weak, which will damage the energy of the food in cooking, thus affecting the health of the occupants. In addition, the stove fire is also representative, so it has a great influence on the couple’s sexual life. Try not to install air conditioning in the kitchen, but if you must, try to blow the wind towards the ceiling or sideways.

　　2, the dining room air conditioning dirty food

　　Blowing the dining table directly is a big no-no, it will inevitably accumulate dust if the air conditioner blows the dining table directly, so it is very likely that the dust will fall into the hot food with the wind, and of course it is easier to cool the delicious meals on the table. Theoretically speaking, eating “dirty rice and cold dishes” for a long time will lead to the hidden worry of being defeated, so the air conditioner in the dining room should not be above or near the dining table.

　　Where is the most correct place for air conditioning? Many people don’t know the secret of air conditioning ~!

　　3, bedroom air conditioning to prevent discomfort

　　When people who use the air conditioner evenly to eliminate evil spirits sleep, the pores are wide open and the respiratory system is relatively unguarded. Therefore, if the air conditioner blows directly on the human body, it will not only make the body uncomfortable and catch a cold, but also attract evil spirits more easily. Therefore, the air outlet will be raised upwards, or the windows in the room will be slightly opened to even the cold air coming straight.

　　4. Air conditioning in the study transports energy

　　Wenchang’s good luck comes to the air conditioner to make people cool, so it has the function of condensing thinking and improving reading concentration. If the air conditioner in the study can be moved to the north and the energy of air conditioning operation can be used, it will drive Wenchang’s good luck and be beneficial to candidates or people who study knowledge. Of course, remember not to blow the air outlet toward your face or head, lest your head be unbearable before you finish reading the book.

　　Xiaobian will introduce the relevant information about the placement of air conditioners here for everyone. The placement of air conditioners directly affects our daily life and fortune. If you are also worried about the placement of air conditioners, you may wish to refer to the suggestions in the article and choose the optimal scheme, so as to feel the comfort brought by air conditioners to a certain extent without affecting human health. I hope that the knowledge summarized by Xiaobian can bring you help.

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　　If you leave home for a day …

　　Kureczka said: “If you just leave home for one day, it is more energy-saving to turn on the air conditioner, but you should raise the temperature by several degrees instead of keeping the comfortable temperature set at home.”

　　If the house is unoccupied for only a day or two, the same direction applies.

　　It’s not necessarily a bad thing to turn off the air conditioner during the day. Either way, the speed of the air conditioner is the same-it just takes longer to cool the hot space. In fact, if you drive at normal temperature all day, you may consume more energy than if you turn it off and have a meeting at night.

　　Air conditioning is not only to cool the space, but also to greatly reduce the humidity level. When the air conditioner is turned off for more than a few hours, the humidity level begins to rise, which may easily lead to mold growth, damage to electronic products, and warping and deformation of wood products. In addition, pets left at home may also be at risk of overheating and discomfort, which may occur especially in hot and humid climate.

　　This is why it is suggested to turn on the air conditioner, but turn up the temperature. The U.S. Department of Energy pointed out that higher indoor temperature will actually slow down the flow of heat into the house, thus saving energy and money.

　　When you get home, don’t turn the air conditioner down too low to “speed up” the cooling process, so that the room won’t get cold faster, and it will only increase energy consumption (cost money).

　　02

　　If you leave home for more than two days …

　　If the whole family (including pets) has been away from home for more than two days, the equipment can be turned off. Kureczka said, “Turn off the air conditioner, and you can save a lot of energy and bills.”

　　This means that when you come back, the temperature inside the room may not be very good and you will feel stuffy. Kureczka suggested, “Installing an intelligent thermostat is a good way to monitor and control the energy efficiency of your home, even if you are not at home-you can turn up the temperature before you leave and then turn it down on your way home.”

　　She also suggested that if you go out for more than a few hours, please close the curtains, which can effectively block the sun, so that the air conditioning unit does not have to work so hard. Especially in areas with extreme temperatures, this will make a huge difference.

　　03

　　At home …

　　The US Department of Energy and the Environmental Protection Agency suggest that the thermostat should be set to 26≧ or higher during the day, 28≧ when sleeping and 29≧ when going out.

　　Think this setting temperature is too high? When the temperature is reduced to 26≧, compared with 22≧, it can save 25% of the electricity bill.

　　Kureczka said: “It varies from person to person to adjust the temperature as high as possible while maintaining comfort. Generally speaking, increasing the temperature by 1 C will help reduce the cooling cost by 5%. “

　　If it is acceptable to adjust the temperature higher than you are used to, then other measures may also make you feel comfortable, such as using ceiling fans. But the ceiling fan will not change the temperature, so remember to turn off the electric fan when you leave the room. Otherwise, you have to pay unnecessary electricity bills.

　　Finally, try to ensure that the house is insulated, so that cold air will not escape and hot air will not sneak in.

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According to a report by the Tass news agency on July 17, Alexei Polisyuk, Director of the Second Department of CIS Affairs of the Russian Ministry of Foreign Affairs, told the Tass news agency that the United States has authorized Ukraine President Zelensky to launch a new strike on Russian territory.

Polisiuk pointed out: Washington is still fueling the escalation of the situation. They tried to justify their crimes while defending Kiev. Not only that, the Zelensky regime was also granted full powers to use American weapons to carry out new strikes on Russian territory.

He emphasized that the United States is still indulging in the dream of its own superior position, hoping that if Russia suffers strategic failure, it can safely hide across the ocean. He warned: Few among the American elite are aware of the risks of such arrogant and underestimating opponents ‘self-deception. For the United States and the world, the consequences may be unpredictable.

Polisiuk emphasized that behind the missile attack on Sevastopol, there was no doubt that U.S. military experts were providing various support services. They used the Pentagon’s drones circling over the area to target targets. (Russia) has made the most solemn representations to the U.S. ambassador to Moscow and the U.S. authorities in this regard, sending the clearest signal that terrorist attacks will lead to inevitable retaliation. As for the safety of the Crimean Peninsula and local residents, this is an absolute priority, and (Russia) is doing its best to provide reliable security. (Compiled by Tong Shiqun)

　　There are many kinds of refrigeration methods, such as gas expansion refrigeration, liquid gasification refrigeration, vortex tube refrigeration and thermoelectric refrigeration. Among them, liquid gasification refrigeration is the most widely used, and its working principle is to realize refrigeration by using the heat absorption of liquid gasification.With the upsurge of industry development, aircon chiller system The expressive force in the market has also been very good, bringing many brand-new high-quality experiences to users. https://puremind.com/product-category/puremind-air-conditioner/industrial-chiller/

　　1, the working principle of air conditioning (mainly refrigeration, heating on the contrary):

　　The high-temperature and high-pressure refrigerant discharged from the compressor flows through the outdoor heat exchanger through the four-way valve, and dissipates heat to the outdoor air through heating transfer, and the refrigerant changes from gaseous state to liquid state-throttles and depressurizes through capillary (or solenoid valve)-one-way valve-filter-two-way valve (outdoor high-pressure pipe)-enters the indoor heat exchanger to absorb heat (realize refrigeration)-outdoor three-way valve (outdoor low-pressure pipe). Complete a single-loop refrigeration cycle.

　　2. Types of components in refrigeration system:

　　The air conditioning refrigeration system is mainly composed of four parts and some auxiliary equipment in the refrigeration system.

　　The four major pieces are:

　　compressor

　　condenser

　　Throttle mechanism

　　Evaporator composition.

　　Auxiliary equipment:

　　Oil separator;

　　Drying filter;

　　Liquid storage tank;

　　Electromagnetic four-way reversing valve;

　　Solenoid valve; Check valve

　　3, the working principle of each component

　　Compressor: As the “heart” of refrigeration system, it has an important influence on the performance, noise, energy consumption, vibration and service life of air conditioning. According to the principle of thermodynamics, it can be divided into volumetric type and velocity type.

　　Volumetric type: a certain volume of gas is sucked into the cylinder and the internal volume of the cylinder is changed to realize gas compression and forced discharge.

　　Speed type: make the inhaled gas get a certain speed, and then slow down, so that kinetic energy can be converted into pressure energy and then discharged. The growth of gas is converted from speed.

　　one

　　Scroll compressor: It is formed by meshing two vortexes of stator and rotor.

　　Rotor compressor: it consists of spindle with eccentric wheel, cylinder, sleeve, air inlet, slide plate, spring, exhaust valve and exhaust port.

　　Condenser: The condenser transfers the refrigerating capacity of the evaporator in the refrigeration system to the environmental medium (cooling water or air) together with the power consumption of the compressor. According to cooling, it can be divided into air-cooled type, water-cooled type and evaporative type. When cooling, it mainly radiates heat to the outside, and when heating, it absorbs heat to the outside.

　　Evaporator: The main function of the evaporator is to boil and evaporate the low-temperature and low-pressure refrigerant liquid that has entered the throttle in the evaporator, absorb the heat of the cooled medium, and then become low-pressure saturated (usually overheated) vapor itself, which is continuously sucked away by the compressor. In other words, the evaporator is a heat exchange device that absorbs heat (that is, outputs cold energy).

　　Throttle element: Throttle element is one of the four main elements in the refrigeration system. Its main function is to throttle and reduce the pressure of high-pressure liquid refrigerant, ensure the pressure difference between condenser and evaporator, and make the refrigerant entering the evaporator absorb heat and evaporate at the required low pressure, thus achieving the purpose of refrigeration and cooling. Adjust the refrigerant flow into the evaporator to adapt to the load change of the evaporator and make the system run normally.

　　Capillary: It is a very thin tube, usually with an inner diameter of 0.5 ~ 2.5 mm and a length of 1 ~ 5 m.. When the refrigerant flows in the tube, it is necessary to overcome the resistance in the tube, which naturally produces a certain pressure drop.

　　Capillary characteristics: Because it is in the normally open state, when the compressor stops, the high and low pressure can be quickly balanced, which is conducive to the compressor starting again. Simple structure, convenient manufacture and low price. For the heat pump system, there is no import and export problem in the throttling process of refrigerant in capillary [this article source: refrigeration encyclopedia WeChat official account” target=_blank>. Using capillary refrigeration system, the performance of the unit is very sensitive to the refrigerant charge. When the operating conditions of the refrigeration system change, the capillary tube has poor ability to adjust the refrigerant flow. Due to the small inner diameter of capillary and long pipeline, it is easy to be blocked, so attention should be paid to the drying and cleaning of the system. Generally, a dry filter is set in front of the capillary to prevent clogging.

　　Thermal expansion valve: the regulating valve that controls the liquid supply of evaporator, and it is also the throttle valve of refrigeration device. Thermal expansion valve uses the change of superheat of refrigerant at evaporator outlet to adjust the flow. According to different structures, it can be divided into internal balance type and external balance type.

　　Disadvantages of thermal expansion valve: low control precision and limited adjustment range. The diaphragm deformation of valve body is limited, which makes the change range of valve needle opening smaller, so the adjustment range of flow is small. When large flow regulation is required, it cannot be met. The high-temperature gas at the place where the signal feedback has a lag evaporator must first heat the shell of the temperature sensor, which has a large thermal inertia, leading to the lag of the reaction.

　　2

　　Electronic expansion valve: the application of electronic expansion valve overcomes the shortcomings of thermal expansion valve and provides conditions for the intelligence of refrigeration device. The electric signal generated by adjusting parameters is mainly used to control the voltage or current applied to the expansion valve, so as to achieve the purpose of adjustment, so that the control system of the electronic expansion valve is complicated and the price is high.

　　Electronic expansion valve classification:

　　Electromagnetic electronic expansion valve;

　　Electric electronic expansion valve.

　　4. Auxiliary equipment of refrigeration system

　　Oil separator: The high-pressure gas (gaseous working medium and lubricating oil) from the compressor enters the oil separator to separate the lubricating oil from the working medium gas and flows down along the inner wall of the cylinder. The working gas is led out of the oil separator from the central pipe through the porous baffle. The separated lubricating oil is concentrated in the lower part of the oil separator and can be discharged regularly, or the lubricating oil can be automatically returned to the crankcase of the compressor by using the ball valve.

　　Drying filter: The function of drying filter is to absorb moisture in refrigeration system, prevent impurities in the system from passing through, and prevent the pipeline of refrigeration system from being blocked by ice and dirt. Because the most easily blocked part of the system is the capillary (or expansion valve), the drying filter is usually installed between the condenser and the capillary (or expansion valve).

　　Liquid storage tank: During the operation of the refrigeration system, the circulating amount of refrigerant in the system will change due to the change of working conditions or the adjustment of refrigeration capacity. Setting the liquid storage tank can balance and stabilize the refrigerant circulation in the system by using the liquid storage capacity of the liquid storage tank, so that the refrigeration system can be in normal operation. In addition, when a component in the refrigeration system fails and needs to be dismantled and repaired, the system refrigerant can be recovered to the liquid storage tank through certain operation methods.

　　The liquid storage tank is generally arranged between the condenser and the throttling element, so that the refrigerant liquid in the condenser can smoothly enter the liquid storage tank. The position of the liquid storage tank should be lower than that of the condenser.

　　Electromagnetic four-way reversing valve: after the electromagnetic coil is energized, it changes the action direction of the valve block in the valve body and changes the flow direction of the refrigerant. So as to achieve the purpose of cooling or heating.

　　three

　　Solenoid valve: Solenoid valve is usually installed in front of the expansion valve to directly control the amount of refrigerant entering the evaporator. It can also be installed before the compressor unloading cylinder to control the unloading of the compressor cylinder.

　　There are two kinds:

　　Direct opening and closing solenoid valve;

　　Indirect solenoid valve.

　　One-way valve: The one-way valve is usually connected in parallel with the auxiliary capillary, and the two are connected in series with the main capillary. One-way valve is a tubular element with a movable spherical or hemispherical plug made of stainless steel or nylon. Combined with capillary tube, it can adapt to two different operating conditions of refrigeration and heating.

　　5. Types and States of Refrigerant

　　Air conditioning refrigerants mainly include R22, R410A and R32.

　　R22 is a medium-temperature refrigerant, with the standard of -40.8 degrees, the solubility of water in R22 is very small, and it is mutually soluble with mineral oil, and R22 does not burn or explode, with little toxicity and strong permeability.

　　R410A is a HFC refrigerant which is composed of R32 and R125 by 50% and 50% by mass. [This article comes from WeChat official account, a refrigeration encyclopedia” target=_blank>, which belongs to a near azeotrope, and its thermodynamic properties are very close to that of a single refrigerant. Compared with R22, R410A’s condensation pressure is increased by 1.6 times, and it is a high-pressure refrigerant, so it is necessary to improve the compression strength of the system.

　　R32 is the abbreviation of difluoromethane, which is a kind of coolant with zero ozone loss potential. It is a gas at room temperature and a colorless and transparent liquid under its own pressure. It is soluble in oil and insoluble in water, and it is an energy-saving and carbon-reducing environment-friendly non-toxic refrigerant, but it is flammable and explosive!

　　6. Refrigerant status

　　Saturated refrigerant: Vapor-liquid conversion in saturated refrigerant is in transport equilibrium, and liquid and gas at this time are in saturation.

　　There is a one-to-one correspondence between saturation temperature and saturation pressure, and the saturation pressure increases with the increase of saturation temperature, and one of them will change and the other will change accordingly. In the system, the refrigerant in the evaporator absorbs heat and the refrigerant in the condenser releases heat, where the refrigerant is saturated.

　　Superheat: Under a certain pressure, the temperature of superheated steam exceeds the saturation temperature.

　　Overheating: the temperature of refrigerant vapor in superheated refrigerant is higher than the saturation temperature under the corresponding saturation pressure, and the liquid refrigerant will overheat after evaporation. In the case of overheating, there is no one-to-one correspondence between the temperature and pressure of refrigerant gas.

　　Near the outlet of the evaporator, the refrigerant continues to absorb heat after complete evaporation and becomes superheated refrigerant with a temperature higher than the saturation temperature. The refrigerant enters the compressor through the suction pipe in case of overheating.

　　Supercooling: The liquid temperature of the supercooled refrigerant is lower than the saturation temperature at the corresponding saturation pressure, and supercooling will only occur when there is no steam in the fluid refrigerant. In the case of supercooling, there is no one-to-one correspondence between the temperature and pressure of refrigerant liquid.

　　Between the outlet of the condenser and the throttle valve, the refrigerant may continue to cool exothermically and become supercooled after condensing into saturated liquid.

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According to a report by Yonhap News Agency on March 20, the South Korean government officially announced on the 20th the results of the allocation of 2000 places to expand the enrollment of 2000 students in the national medical school year. As a result, the medical school enrollment expansion plan has been settled in 27 years. In order to expand local medical infrastructure, the government will allocate 82% of the new places to non-capital area colleges and universities, and the remaining 18% will be allocated to Gyeonggi Province and Incheon areas. The number of schools in Seoul will remain unchanged.

Minister of Education Lee Zhouhao announced the results of the allocation of enrollment places for medical schools in the 2025 academic year, including the above contents, at the Central Government’s Seoul Office Building on the same day. The Ministry of Education received applications for medical school enrollment quotas from 40 universities across the country from February 22 to March 4. After that, it discussed with experts through the Expansion Allocation Committee and released the results.

The results show that the 27 university medical schools in non-capital areas will expand enrollment by 1639 students, accounting for 82% of the total enrollment expansion. At present, the number of students enrolled in non-capital medical schools is 2023, accounting for 662% of the national medical school enrollment scale (3058 students), and will increase to 3662 starting next year, accounting for 724% of the total enrollment scale.

In the Capital Region, the government has allocated 361 expanded enrollment places to five universities in Gyeonggi Province and Incheon City with enrollment sizes of less than 50 students, but the eight universities in Seoul have zero new places.

The Ministry of Education explained that the allocation of quotas is mainly considered to alleviate the imbalance between medical resources in the capital and non-capital areas, so that citizens can enjoy high-quality medical services in any region. The allocation committee comprehensively considered the materials submitted by each institution, educational conditions and future plans, and contribution to regions and essential medical care.

This is the government’s expansion of the enrollment scale of medical schools in 27 years. Analysts believe that although the medical profession still strongly resists the enrollment expansion policy through collective resignations, the government announced the allocation results on the same day, and the enrollment of medical students has been settled. The Ministry of Education plans to work with relevant departments to improve medical education conditions and provide support for institutions to hire professors and expand facilities.

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Washington, May 13 (Reporter Deng Xianlai) U.S. President Biden signed a bill on the 13th to ban the United States from importing low-enriched uranium produced in Russia.

Jack Sullivan, U.S. National Security Assistant to the President, issued a statement on the same day saying that Biden signed the “Ban the Import of Russian Uranium Act” and made it law, aiming to reduce and ultimately eliminate the U.S. dependence on Russia in the civil nuclear energy field.

The bill has previously been passed in the U.S. House of Representatives and Senate. According to regulations, 90 days after the bill takes effect, U.S. companies will not be allowed to import low-enriched uranium produced in Russia. The bill provides exemptions for utilities such as nuclear power plants that have to shut down nuclear reactors due to cutting off Russia’s uranium supply. The exemption policy will expire no later than January 1, 2028. The bill also authorizes the federal government to allocate $27.2 billion in funding previously approved by Congress to enhance the U.S. domestic uranium enrichment capabilities.

According to the Washington Post, U.S. companies currently import about US$1 billion worth of enriched uranium from Russia’s national atomic energy every year.