The device and principle of operation of the refrigerator: two-chamber, absorption

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The device, as well as the prin­ci­ple of oper­a­tion of the refrig­er­a­tor, is super­fi­cial­ly stud­ied in physics lessons, how­ev­er, not every adult can imag­ine how the refrig­er­a­tor works? Con­sid­er­a­tion and analy­sis of the main tech­ni­cal aspects will help in prac­tice to extend the life and improve the per­for­mance of a house­hold refrig­er­a­tor.

Compression cooler device

The refrig­er­a­tor device is best con­sid­ered on the exam­ple of a com­pres­sion sam­ple, since such devices are most often used in every­day life:

  1. Com­pres­sor — a device that push­es the refrig­er­ant (gas) with the help of a pis­ton, cre­at­ing dif­fer­ent pres­sures in dif­fer­ent parts of the sys­tem;
  2. Evap­o­ra­tor — a con­tain­er into which the liq­ue­fied gas enters, absorb­ing heat from the refrig­er­a­tion cham­ber;
  3. Capac­i­tor — a con­tain­er in which the com­pressed gas gives off heat to the sur­round­ing space;
  4. expan­sion valve — a device that main­tains the required pres­sure of the refrig­er­ant;
  5. refrig­er­ant — a mix­ture of gas­es (fre­on is most often used), which, under the influ­ence of the oper­a­tion of the com­pres­sor, cir­cu­lates in the sys­tem, tak­ing and giv­ing off heat in its dif­fer­ent parts.

Refrigerator operation

The device of the refrig­er­a­tor, as well as the prin­ci­ple of oper­a­tion of a refrig­er­a­tor with one cham­ber, can be under­stood by watch­ing the cor­re­spond­ing video:

The most impor­tant aspect in under­stand­ing the oper­a­tion of a com­pres­sion appa­ra­tus is that it does not gen­er­ate cold per se. Cold is caused by tak­ing heat inside the device and send­ing it out­side. Fre­on per­forms this func­tion. Get­ting into the evap­o­ra­tor, which usu­al­ly con­sists of alu­minum tubes or plates sol­dered togeth­er, fre­on vapor absorbs heat.

You need to know: in old-style refrig­er­a­tors, the evap­o­ra­tor hous­ing is also the freez­er hous­ing. When defrost­ing this cham­ber, do not use sharp objects to remove ice, since all the fre­on will dis­ap­pear through the pierced evap­o­ra­tor hous­ing. A refrig­er­a­tor with­out refrig­er­ant becomes inop­er­a­tive and is sub­ject to cost­ly repairs.

Fur­ther, under the influ­ence of the com­pres­sor, fre­on vapor leaves the evap­o­ra­tor and pass­es into the con­denser (a sys­tem of tubes that are locat­ed inside the walls and on the back of the unit). In the con­denser, the refrig­er­ant cools down, grad­u­al­ly becom­ing liq­uid. On the way to the evap­o­ra­tor, the gas mix­ture is dried in a fil­ter-dri­er and also pass­es through a cap­il­lary tube. At the entrance to the evap­o­ra­tor, due to the increase in the inner diam­e­ter of the tube, the pres­sure drops and the gas becomes vaporous. The cycle is repeat­ed until the required tem­per­a­ture is reached.

Read also:

How does a compressor work?

With the help of a pis­ton, the com­pres­sor dis­tills the refrig­er­ant from one pipe sys­tem to anoth­er, alter­nate­ly chang­ing the phys­i­cal state of fre­on. When the refrig­er­ant is sup­plied to the con­denser, the com­pres­sor com­press­es it strong­ly, caus­ing the fre­on to heat up. After going a long way through the labyrinth of con­denser tubes, cooled fre­on enters the evap­o­ra­tor through an expand­ed tube. The sud­den change in pres­sure cools the refrig­er­ant rapid­ly. Now fre­on vapors are able to absorb a cer­tain dose of heat and pass into the con­denser tube sys­tem.

Compressor

In house­hold appli­ances, ful­ly sealed com­pres­sor hous­ings are used that do not allow the work­ing gas mix­ture to pass through. For the pur­pose of tight­ness, the elec­tric motor that dri­ves the pis­ton is also locat­ed inside the com­pres­sor hous­ing. All rub­bing parts inside the motor-com­pres­sor are lubri­cat­ed with spe­cial oil.

The elec­tri­cal cir­cuit of the refrig­er­a­tor can be use­ful for those who are ready for self-diag­no­sis and repair of the refrig­er­a­tor:

Refrigerator wiring diagram

The device and principle of operation of a two-chamber refrigerator

The device of a two-cham­ber refrig­er­a­tor dif­fers from a sin­gle-cham­ber one in that each com­part­ment has its own evap­o­ra­tor. Unlike their pre­de­ces­sors, in two-cham­ber devices, both com­part­ments are iso­lat­ed from each oth­er. In such devices, the freez­er is usu­al­ly locat­ed at the bot­tom, and the refrig­er­a­tion part is at the top. The prin­ci­ple of oper­a­tion of a two-cham­ber refrig­er­a­tor is that the work­ing gas mix­ture first cools the freez­er evap­o­ra­tor to a cer­tain sub-zero tem­per­a­ture. Only after that the fre­on pass­es into the evap­o­ra­tor of the refrig­er­a­tion com­part­ment. After the evap­o­ra­tor of the refrig­er­at­ing cham­ber reach­es a cer­tain minus tem­per­a­ture, the ther­mo­stat is acti­vat­ed, which stops the oper­a­tion of the motor.

Two-chamber refrigerator

In every­day life, two-cham­ber devices with one com­pres­sor are more often used. In units with two motors, the prin­ci­ple of oper­a­tion of the refrig­er­a­tor does not change sig­nif­i­cant­ly, just one com­pres­sor works for the freez­er, the oth­er for the refrig­er­a­tor. It is gen­er­al­ly accept­ed that the oper­a­tion of a refrig­er­a­tor with one com­pres­sor is more eco­nom­i­cal, but in real­i­ty this is not always the case. After all, in a device with two motors, you can turn off one of the cam­eras, in which there is no need. The oper­a­tion of a two-cham­ber refrig­er­a­tor with one com­pres­sor always involves the simul­ta­ne­ous cool­ing of both cham­bers.

Refrigerator and ambient temperature

The oper­at­ing instruc­tions for most house­hold refrig­er­a­tors indi­cate at what tem­per­a­ture it is best to oper­ate it. The min­i­mum allow­able indi­ca­tor is a tem­per­a­ture of +5 Cel­sius. Can the refrig­er­a­tor work in cold con­di­tions, espe­cial­ly in the cold? Con­sid­er pos­si­ble prob­lems:

  • The ther­mo­stat is not work­ing prop­er­ly. Under nor­mal con­di­tions, the ther­mo­stat breaks the elec­tri­cal cir­cuit when the required tem­per­a­ture is reached. When the air inside warms up, the ther­mo­stat will close the elec­tri­cal cir­cuit again, and the motor will resume its oper­a­tion. In con­di­tions of sub-zero ambi­ent tem­per­a­ture, the ther­mo­stat most like­ly will not turn on the com­pres­sor again, since the heat inside the cham­ber sim­ply has nowhere to come from;
  • Com­pres­sor dif­fi­cult to start. In old­er devices, R12 and R22 refrig­er­ants were most often used. For nor­mal oper­a­tion, refrig­er­ant oils were used, which become too thick at tem­per­a­tures below + 5 ° C, which means that the start and move­ment of the pis­ton will be dif­fi­cult;
  • The appear­ance of the effect of “wet run”. Since there is no heat in the refrig­er­a­tor, the oper­a­tion of the evap­o­ra­tor is dis­rupt­ed. The vapor sat­u­rat­ed with droplets enters the com­pres­sor. As a result of pro­longed oper­a­tion in such con­di­tions, the entire mechan­ics of the motor will be dam­aged.

In sim­ple words, a gen­tle atti­tude to the device will sig­nif­i­cant­ly extend its life.

The principle of operation of the absorption refrigerator

In the absorp­tion appa­ra­tus, cool­ing is asso­ci­at­ed with the evap­o­ra­tion of the work­ing mix­ture. Most often, this sub­stance is ammo­nia. The move­ment of the refrig­er­ant occurs as a result of the dis­so­lu­tion of ammo­nia in water. From the absorber, the ammo­nia solu­tion enters the des­or­ber, and then to the reflux con­denser, in which the mix­ture is sep­a­rat­ed into its orig­i­nal com­po­nents. In the con­denser, the ammo­nia becomes liq­uid and is sent back to the evap­o­ra­tor.

Absorption refrigerator

Flu­id move­ment is pro­vid­ed by jet pumps. In addi­tion to water and ammo­nia, hydro­gen or anoth­er inert gas is present in the sys­tem.

Most often, an absorp­tion refrig­er­a­tor is in demand where it is impos­si­ble to use a con­ven­tion­al com­pres­sion ana­logue. In every­day life, such devices are rarely used, since they are rel­a­tive­ly short-lived, and the refrig­er­ant is a tox­ic sub­stance.

Operation and rest mode of the compression refrigerator

Many users are inter­est­ed in the ques­tion: how long should the refrig­er­a­tor work? The only true cri­te­ri­on for the nor­mal oper­a­tion of a home appli­ance is a suf­fi­cient degree of freez­ing and cool­ing of food in it.

How long a refrig­er­a­tor can work and how long it should rest is not spelled out in any instruc­tion, how­ev­er, there is the con­cept of “opti­mal work­ing time ratio”. To cal­cu­late it, the dura­tion of the work­ing cycle is divid­ed by the sum of the work­ing and non-work­ing cycle. So, for exam­ple, a refrig­er­a­tor that has worked for 15 min­utes with a fur­ther 25-minute rest will have a coef­fi­cient of 15/(15+25) = 0.37. The small­er this coef­fi­cient, the bet­ter the refrig­er­a­tor works. If the result of the cal­cu­la­tion is a num­ber less than 0.2, then most like­ly the tem­per­a­ture in the refrig­er­a­tor is incor­rect­ly set. A coef­fi­cient greater than 0.6 means that the tight­ness of the unit is bro­ken.

How does the No Frost refrigerator work?

In refrig­er­a­tors with a no frost sys­tem (“no frost”), there is only one evap­o­ra­tor, which is hid­den in the freez­er behind a plas­tic wall. The cold from it is trans­ferred using a fan, which is locat­ed behind the evap­o­ra­tor. Through the tech­no­log­i­cal open­ings, cold air enters the freez­er, and then into the refrig­er­a­tor.

refrigerator No Frost

To jus­ti­fy its name, the No Frost refrig­er­a­tor is equipped with a defrost­ing sys­tem. Sev­er­al times a day, the timer acti­vates the heat­ing ele­ment locat­ed under the evap­o­ra­tor. The result­ing liq­uid evap­o­rates out­side the refrig­er­a­tor.

Just a few min­utes, spend


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