Dryer

  The working principle is that the compressed air from the air compressor first exchanges heat with the dried low-temperature compressed air in the heat exchanger,reducing the temperature.Then,it enters the evaporator and is further cooled to about 2℃.At this dew point,most of the water in the compressed air has become liquid and is discharged.The compressed air with very little water content is then sent into the adsorption tower for further drying and dehydration.Finally,the low-temperature dry compressed air enters the heat exchanger,Cooling high-temperature and humid air,while also increasing its own temperature,can prevent condensation on the outer wall of the compressed air delivery pipeline.After heating,a small portion of the compressed air is used as adsorbent for regeneration,improving regeneration efficiency and reducing energy consumption.

  By using refrigerant and compressed air for heat exchange,the temperature of compressed air is reduced to a dew point temperature range of 2-10℃,so that the water content in compressed air tends to become supersaturated,thereby removing moisture(water vapor component)from the compressed air.

  When the pressure of compressed air is high,the temperature is low,the ambient temperature is low,and the amount of air processed is small,a low pressure dew point can be obtained.The atmospheric dew point can only reach-17℃.

  The functions of the main components of the refrigerated dryer:

  1.Refrigeration compressor

  The refrigeration compressor is the heart of the refrigeration system,and currently most compressors use fully sealed reciprocating compressors.Raise the refrigerant from low pressure to high pressure and continuously circulate the refrigerant,thereby continuously releasing internal heat into an environment higher than the system temperature.

  2.Condenser

  The function of the condenser is to cool the high-pressure and overheated refrigerant vapor discharged from the refrigerant compressor into a liquid refrigerant,and its heat is carried away by the cooling water.Enable the refrigeration process to proceed continuously.

  3.Evaporator

  The evaporator is the main heat exchange component of a refrigerated dryer.Compressed air is forced to cool in the evaporator,and most of the water vapor is cooled and condensed into liquid water,which is discharged from the machine,thereby drying the compressed air.Low pressure refrigerant liquid undergoes a phase change in the evaporator and becomes low-pressure refrigerant vapor.During the phase change process,it absorbs surrounding heat,thereby cooling the compressed air.

  4.Thermal expansion valve(capillary)

  The thermal expansion valve(capillary)is the throttling mechanism of a refrigeration system.In a refrigerated dryer,the supply of refrigerant to the evaporator and its regulator is achieved through a throttling mechanism.The throttling mechanism allows refrigeration to enter the evaporator from high-temperature and high-pressure liquids.

  5.Heat exchanger

  The vast majority of refrigerated dryers have heat exchangers,which are heat exchangers that exchange heat between air and air.Generally,they are tube and tube heat exchangers(also known as shell and tube heat exchangers).The main function of a heat exchanger in a refrigerated dryer is to"recover"the amount of cold air carried by the compressed air cooled by the evaporator,and use this amount of cold air to cool the compressed air carrying a large amount of water vapor at higher temperatures(i.e.saturated compressed air discharged from the compressor,cooled by the compressor's built-in rear cooler,and then separated by gas and water,with a temperature generally above 40℃),thereby reducing the heat load on the refrigeration system of the refrigerated dryer,To achieve the goal of energy conservation.On the other hand,the temperature of low-temperature compressed air rises in the heat exchanger,preventing condensation on the outer wall of the pipeline conveying compressed air due to the temperature being lower than the ambient temperature.In addition,the increase in compressed air temperature reduces the relative humidity of the dried compressed air(generally less than 20%),which is beneficial for preventing metal corrosion.Some users(such as those paired with air separation equipment)require compressed air with low water content and low temperature,and in this case,the refrigerated dryer is no longer equipped with a heat exchanger.Due to the absence of a heat exchanger,the cooling capacity of the cold air cannot be recycled,resulting in a significant increase in the heat load of the evaporator.In this case,not only is it necessary to increase the power of the refrigeration compressor for energy compensation,but other components of the entire refrigeration system(evaporator,condenser,and throttling components)also need to be correspondingly increased.From the perspective of energy recovery,we always hope that the higher the exhaust temperature of the refrigerated dryer,the better(a higher exhaust temperature indicates more energy recovery).It is recommended that there is no temperature difference between the inlet and outlet.But in reality,this cannot be achieved.When the air inlet temperature is below 45℃,it is not uncommon for the temperature difference between the inlet and outlet of the refrigerated dryer to be more than 15℃.

  Compressed air process:

  Compressed air→Mechanical filter→Heat exchanger(releasing heat)→Evaporator→Gas liquid separator→Heat exchanger(absorbing heat)→Outlet mechanical filter→Air storage tank

  Refrigerant process:

  →Hot gas bypass valve→

  ↑↓

  Compressor high-pressure outlet(lower part)→Gasifier→Evaporator→Drying filter→condenser→Liquid separator→Compressor low-pressure inlet(upper part)

  Maintenance and inspection:

  1、Maintain the dew point temperature of the refrigerated dryer above zero degrees.

  To lower the temperature of compressed air,it is inevitable that the evaporation temperature of the refrigerant will also decrease very low.When the refrigerated dryer cools compressed air,there is a film like condensate on the surface of the fins inside the evaporator.If the surface temperature of the fins is below zero due to the decrease in evaporation temperature,the surface condensate may freeze.At this time:

  A.Due to the attachment of a layer of ice with much lower thermal conductivity on the surface of the inner liner fins of the evaporator,the heat transfer efficiency is greatly reduced,and compressed air cannot be fully cooled.At the same time,due to insufficient heat absorption,the evaporation temperature of the refrigerant may further decrease.The result of such a cycle will inevitably bring many adverse consequences to the refrigeration system(such as"liquid compression");

  B.Due to the small spacing between the inner fins of the evaporator,once ice forms on the fins,it will reduce the circulation area of compressed air,and in severe cases,it may even cause blockages in the air path,known as"ice blockage";In general,the compression dew point temperature of the refrigerated dryer should be above 0℃.In order to prevent the dew point temperature from being too low,energy bypass protection(achieved by bypass valves or fluorine circuit solenoid valves)is installed in the refrigerated dryer.When the dew point temperature is below 0℃,the bypass valve(or fluorine circuit solenoid valve)automatically opens(with an increased opening),and the uncondensed high-temperature and high-pressure refrigerant vapor is directly injected into the inlet of the evaporator(or the gas-liquid separation tank at the inlet of the compressor),causing the dew point temperature to rise above 0℃.

  C.In terms of system energy consumption,low evaporation temperature leads to a significant decrease in compressor cooling coefficient and an increase in energy consumption.

  Inspection:

  1.The pressure difference between the inlet and outlet of compressed air shall not exceed 0.035Mpa;

  2.Evaporation pressure gauge 0.4Mpa-0.5Mpa;

  3.High pressure gauge 1.2Mpa-1.6Mpa

  4.Regularly observe drainage and sewage systems