If the superheat process 1~1' of the evaporator to compressor suction line is considered, the refrigeration cycle is 1'→2'→3→4→1. If the liquid refrigerant discharged from the condenser is subcooled by the subcooler After (3→3'), the throttling is performed, and the refrigeration cycle is: 1'→2'→3'→4'→1'. If the superheating and supercooling processes are not considered (ie 1→1' and 3→3'), the refrigeration cycle refrigeration coefficient = q2w = i1 - i4i2-i1. If the superheat and supercooling processes are considered, the refrigeration cycle refrigeration coefficient '= Q'2w'=i'1-i'4i'2-i'1≈i'1-i'4i2-i1<1>.
The above theoretically analyzes the representation of the refrigeration cycle on the lgp-i diagram and the expression of the refrigeration coefficient. How to effectively improve the refrigeration effect of the refrigeration cycle in practical applications? Let's take the example of household refrigerators and small refrigerators to improve how to effectively improve value.
How to effectively improve the refrigeration effect of the refrigeration cycle Reduce the condensation temperature and increase the evaporation pressure. As shown in the figure, if the condenser cooling condition is changed, for example, fan convection forced cooling (change the water temperature and flow rate to the water cooling unit), the condensation temperature is lowered by tnj. To tnj'; at the same time, shorten the capillary length within the allowable range or thicken the capillary tube (change the amount of adjustment of the thermal expansion valve to the cold storage), so that the evaporation pressure is raised from Pzf to Pzf', at which time the refrigeration cycle a→b→c →d→a, as can be seen from the figure, the refrigeration coefficient “= ia-idib-ia†is significantly lower than the refrigeration coefficient of the refrigeration cycle 1→2→3→4→1, which means that the condensation temperature is lowered and the evaporation is increased. The pressure effectively increases the cooling effect of the refrigeration cycle.
The process of achieving supercooling and superheating is shown in the diagram of the refrigeration system of the refrigerator: let the capillary close to (or wrap) the evaporator back to the pipe wall, or let the capillary pass through the evaporator return pipe. In this way, the colder gaseous refrigerant in the evaporator can be used to further cool the higher temperature refrigerant from the condenser to achieve the supercooling process; at the same time, the gaseous refrigerant in the evaporator return pipe is heated, resulting in a superheating process. It can be seen that the refrigeration cycle with supercooling and superheating process has a cooling coefficient much larger than that without superheat and supercooling: ie, '=i'1-i'4i2-i1>=i1-i4i2-i1. Visible capillary adhesion The evaporator return pipe can effectively improve the cooling effect.
Ensure that the proper clearance volume and the airtight clearance of the high pressure valve plate and the valve seat are too large, and the displacement of the compressor is reduced. To achieve the same cooling capacity, the consumption of compression work must be increased. According to the formula =q2w=i1-i4i2-i1 and it is known that it is necessary to reduce. Conversely, if the clearance volume is too small, it will cause the phenomenon of the compressor cylinder and the like. Therefore, it is very important whether the clearance volume of the compressor cylinder is proper during the actual operation, so as to ensure the displacement without causing the card. The failure of the cylinder is the principle.
In addition, the airtightness of the high pressure valve plate and the valve seat of the compressor can not neglect the cooling effect of the refrigeration cycle. If the sealing is bad, the string gas is formed (for example, to eliminate the ice blockage phenomenon, the system is filled with excess methanol and the system is evacuated, etc.) In which the water reacts with the refrigerant to form an acidic substance, all of which may cause the failure), and the exhaust efficiency is lowered, the compression work is increased, and the knowledge is inevitably decreased; the motor winding is damaged, and the refrigeration cycle cannot be performed (referring to Fully enclosed compressor).
Increasing the vacuum degree of the refrigeration system is not enough to make the residual gas (air) in the refrigeration system pipe mix with the refrigerant. According to Dalton's law, the pressure of the mixed gas is Pnj〃=Pnj+Pc, where Pc is residual. Gas pressure, Pnj is the refrigerant gas pressure. Obviously Pnj〃>Pnj, from the above, the refrigeration coefficient is inevitably lowered, and the cooling effect is deteriorated. At the same time, trace moisture in the residual gas will cause ice blockage failure in the refrigeration system piping (eg capillary inlet, thermal expansion valve inlet); the presence of residual gas (mainly air) will also oxidize the lubricating oil, at the high temperature of the compressor Under the high pressure condition, the valve seat is carbonized, and the cooling effect is gradually deteriorated. Therefore, the vacuum treatment of the refrigeration system is an important part of improving the cooling effect of the refrigeration cycle. As for the pumping time, in theory, the longer the time, the better, but in practice, depending on the displacement of the vacuum pump and the capacity of the refrigeration system, it is omitted.
Strict control of refrigerant, refrigeration oil purity, correct determination of capillary insertion filter length and filter position refrigerant and refrigeration oil impure will seriously affect the refrigeration cycle, capillary insertion dry filter too long or too short will directly affect the refrigerator refrigeration effect. When the capillary is inserted into the dry filter, the refrigerant and the impurities in the frozen oil and other detached materials can easily block the capillary and the filter passage. As a result, the refrigerant expands, vaporizes, and absorbs heat at the blockage, resulting in poor evaporator refrigeration<2 >. Therefore, in practice, the purity of the refrigerant and the frozen oil should be strictly controlled, the capillary should be properly installed, and the filter should be placed obliquely (or vertically) upwards in order to prevent clogging.
Strictly control the amount of refrigerant charge, the refrigerant charge is too small, the refrigerant circulation is insufficient, the degree of superheat increases, and the unit temperature rises, so that the compression work w=i1-i2 increases, causing a decrease, which seriously affects the refrigeration effect; If the refrigerant is too much, the refrigerant in the pipeline will reach saturation state, and the capillary will not be restricted. It will also cause the evaporator to not absorb heat very much, resulting in poor cooling and directly affecting the cooling effect. Therefore, in practice, the refrigerant charge should be strictly controlled. If the conditions permit, the gauge pressure method, the weighing method or the quantitative liquid addition method can be used, and the "experience method" should be avoided as much as possible to charge the refrigerant.
Ensuring that the condenser and the evaporator are clean and clean has a great influence on the cooling effect. If the outer surface of the evaporator or the condenser is too dirty or a large amount of refrigerating machine oil is deposited inside, the heat transfer between the two will be seriously affected, resulting in deterioration of the heat transfer effect. When the condensing pressure is increased and the evaporation pressure is lowered, it is known that the cooling coefficient is inevitably lowered. Therefore, in practice, the cleanliness of both should be guaranteed.
Conclusion In summary, the factors affecting the actual refrigeration cycle of the refrigeration system are complex. In practical applications, when determining the condensation temperature and evaporation pressure, selecting the compressor and its associated motor, and performing system evacuation, these effects should be considered comprehensively. Factors, while ensuring the actual needs, while minimizing or avoiding the loss of cooling capacity and the increase of power consumption, improve the actual refrigeration coefficient of the system, thereby effectively improving the refrigeration cycle effect and realizing the economic operation of the refrigeration system.
Other Knitted Gifts
Nowadays, knitted gifts are becoming more and more popular, and many people buy them or make them by hand to give away relatives and friends. Because they are very comfortable and highly crafted, they are also very textured to the touch. Knitted gifts are more meaningful than other gifts and can be favored by people.
We undertake OEM services, and can produce high cost-effective knitted gifts for you in large quantities. The products we produce have quality assurance and are of high quality and low price.
Yacheng Knitting Co., Ltd. can mass produce customized high-quality knitted garments, including sweaters, Custom Knit Sweaters, Knitted Pants, Knitted Skirt, Knitted Shoes , Knitted Scarves and Knitting Blanket. If you need to order knitted products, please contact us.
Knit Gifts,Knitting Kit Gift,Knitted Xmas Gifts,Red Wine Gift Sets
DongGuan YaCheng Knitting Co., Ltd , https://www.oemknittingyc.com