毛细管长度计算（Capillary length calculation）

Calculation formula of capillary length in refrigerator and freezer

Fridge, freezer, formula, capillary, length

Formula for calculating capillary length of refrigerators and freezers -- Test Method for capillary length

The process of open tube, high pressure pipe is connected with a pressure meter is connected with one end of the capillary, dry filter, the other end is not welded, start the compressor, if the steady pressure gauge at about 0.98-----1.177Mpa, can be considered appropriate, the pressure is too high to cut a little pressure, hour plus a short trial, until the appropriate date, then the capillary and an evaporator connected. Vacuum and charge refrigerant.

Two

Most factories use test method to determine the length of the capillary, the equipment needed: high-pressure bottle, flowmeter, hydraulic measurement and pressure measurement conditions, and in the maintenance because of conditions, it's difficult; here is a convenient measuring method:

For a double tail drying filter in the refrigerator condenser output needs to replace the capillary end of the welded joint and the condenser pipe (pipe selection 5 mm diameter copper tube and three gauge frame, in the choice of a basically and the diameter of the capillary tube length are similar in length, according to the power of the compressor estimates, usually in the 2 meters -2.8 meters between the end to a dry filter. The output end of the insertion depth of 0.5~1 cm in general should not be too deep, too deep will touch the drying filter filter clogging, can not be too short, too short to loot by capillary caliber, correct welding, open compressor the export process, open the compressor connected to the drying filter check the pressure gauge on the pressure, depending on the choice of different refrigerant pressure, such as pressure too high Shorten some capillaries and, on the contrary, lengthen them, when they are basically within the range of pressure provided below. The following provides different refrigerant pressure ranges:

R12 11.5~12.5KG/CM2

R134 10.5~11.5KG/CM2

R22 15.5~18KG/CM2

R600 9.6~10.5KG.CM2

In actual maintenance, constant testing and standard length are available for future testing and length, but must be consistent with the diameter of the test capillary

3. homemade fast method for refrigerator evaporator and capillary!!!

In the maintenance of refrigeration equipment, such as refrigerators and freezers encountered in the evaporator leakage, the general can not remove the original evaporator coil, on the basis of internal packaging can be recognized re coil. However, calculating the length of the copper tubes used will cause many maintenance workers to feel headache. Here is a quick way to everyone, for reference.

A fast method

1. calculation formula of new tube length of refrigerator evaporator

Total length of pipe = length of freezer room + length of cold storage room

Freezing chamber length =1/3, total volume (L) * 0.148 M / L

Refrigerating chamber length =2/3, total volume (L) * 0.03 M / L

2. calculation formula of new tube length of electric refrigerator evaporator

Copper tube total length =1/3, total capacity * 0.148 M / L, +2/3 gross capacity * 0.03 M / L

Note: the calculation method of the length of brass in the formula, suitable for the diameter of copper for 6mm and 8mm Phi Phi

Four

The refrigerator requires a compression ratio of 1:10 to allow the refrigeration system to meet design specifications.

The compressor of the refrigerator is high pressure compressor, the compression ratio is far to meet the requirements, so the compression ratio of the 1:10 will have to control the throttle capillary, capillary length can increase the compression ratio, reducing capillary can reduce the compression ratio.

The low pressure 0.06MPa refrigeration system as reference, the absolute pressure of 0.16MPa, the compression ratio is 1:10, so the pressure is 10 times of low pressure, high pressure 1.6MPa, pressure gauge reading is 1.5MPa.

In actual commissioning of the capillary, the opening of the low-pressure end of the compressor is placed in the atmosphere. The reading of the atmospheric pressure on the meter is 0, and the actual pressure is 0.1MPa.

The pressure gauge and the capillary in the high-pressure side of a compressor, the flow generated by capillary pressure readings, pressure should be 10 times of low pressure, so the pressure is 1MPa, a reading of 0.9MPa.

In fact, a good refrigerator, the compression ratio can reach 1:12, so debugging the length of the capillary, high voltage readings for 1.1MPa is also possible. Therefore, the length of the capillary can be a certain degree of scalability, not necessarily the standard.

Generally use the refrigerator capillary 3M for debugging, observe the pressure gauge, cut short thick tube. The refrigerator with long service life has poor cooling effect

When the refrigerant is discharged, the refrigeration dose has not been reduced, and the leakage of the system has not been detected. The compressor exhaust efficiency is suspected, but the replacement compressor is invalid. The reason for this failure is that the service life of the press is long, and the insulating paint of the compressor coil is dissolved with the compressor oil and refrigerant, and wax is deposited on the inner wall of the capillary tube",

Reduce the capillary bore, cause the refrigerant flow to decrease, the machine appears the refrigeration difference. After washing is invalid, can be cut short capillary network, 0.4M, exclude pull to failure can be: capillary

Characteristics of capillary throttling

A capillary is a small bore tube with a specified length. It has no moving parts and can produce a predetermined pressure drop in the refrigeration system. It is generally used as a throttling element for refrigerators, air conditioners and small refrigerators.

The capillary flows through its length to produce a pressure drop to control the flow of refrigerant and maintain the pressure difference between the condenser and the evaporator. When there is a certain degree of supercooling of the refrigerant into the capillary, will produce pressure along the flow direction and the change of state, the first is to gradually reduce the supercooled liquid with pressure, first into the corresponding saturated liquid under pressure, this section of said liquid phase, the pressure is not reduced, and there was a linear change from the first; a bubble until the end of the capillary are gas-liquid coexistence, also known as the two-phase flow period, period of saturated steam content increased gradually along the flow direction, so the pressure drop is nonlinear, the more to the capillary end, the unit length of the pressure drop is bigger. When the pressure is reduced to the saturation pressure at corresponding temperature, will produce flash phenomenon, cooling the liquid self evaporation is decreased with the pressure, the temperature of the refrigerant is reduced, which is reduced to the corresponding saturation temperature under pressure.

The characteristics of a capillary as a throttling device

The capillary is drawn from the copper tube and has the advantages of simple structure, convenient operation and low price.

Without moving parts, they are not prone to malfunction or leakage.

Has the characteristics of automatic compensation, as well as the refrigerant under certain pressure difference (delta P=PK-PO), when the stable flows through the capillary flow, when the cooling load changes, the condensation pressure PK increases or decreases the evaporation pressure of PO, the P value increases, the refrigerant in the capillary flow also increases, in order to adapt to the requirements of refrigeration load on flow but, the compensation capacity is relatively small.

The refrigeration compressor stops running, high side pressure and low pressure in the refrigeration system can quickly be balanced, start again, start the motor load small refrigeration compressor, it is not necessary to use high starting torque of the motor, a semi closed and full closed refrigeration compressor is especially important.

Capillary selection method

The diameter and length of the capillary must be selected, but the capillary theory calculation is relatively complex, structure calculation error is also big, so generally in a selected diameter, to decide to decide the length of capillary size according to the test results under specified conditions.

Nitrogen determination method and liquid measurement method: measurement methods in capillary connected to the entrance pressure vessel as the gauge of 980KPa, the environmental temperature is constant, the measurement of fluid flow in capillary per minute value.

Direct determination of capillary flow on a refrigeration system: a pressure gauge is attached to the exhaust pipe of the refrigeration system. The suction port is connected with a dry air or nitrogen gas source whose pressure is zero. Open compressor, refrigeration system pressure (refrigerator) best to 1200--1300KPa (evaporation temperature is -15 DEG to -18 DEG C), if you want to change the evaporator pressure, only need to lengthen or shorten the length of the capillary can be achieved. This method is easy to operate and has low precision. It can be used in maintenance.

The refrigeration system of the air conditioner and the cold drink machine generally uses the "air conditioning mode", the capillary is thicker and the resistance is small. The air flow rate of the capillary tube is determined by this method, and the pressure of the table can reach 540--590KPa.

The most basic way is to change the length and diameter of the original capillary. The new one is OK.

Determination of capillary flow by capillary gas flow method

expansion valve

Types of expansion valves

Manual expansion valve: is the simplest throttle valve, it is used in the refrigeration system manual control of the occasion. The utility model is actually a needle valve with fine tooth thread regulation, and the opening degree of a manual regulating valve. When the compressor stops, the manual expansion valve must be closed and the liquid passage is cut off.

Automatic expansion valve: according to * acting on the diaphragm (or bellows) an automatic valve control liquid flow on the suction pressure corresponding to, when the valve is opened, the liquid refrigerant into the evaporator, the evaporator pressure increased, at the same time will lead to expansion of small valve closing. As the compressor draws steam from the evaporator, the pressure drops, which tends to cause the expansion valve to open so that it can automatically adjust the opening of the valve. The refrigeration system is running, the valve never closed. When the compressor is started, immediately open the valve; when the compressor is stopped, the pressure in the evaporator can make the expansion valve closed.

Thermal expansion valve: is an improved automatic expansion valve, widely used in refrigeration and air-conditioning equipment, the diaphragm or bellows pressure from the upper part of the temperature of the package pressure response. The temperature sensitive package is filled with refrigerant which is similar to the refrigeration system, and the temperature sensitive package is attached to the suction pipe near the outlet of the evaporator,

The capillary chamber is connected with the expansion valve diaphragm (or bellows) chamber. When the refrigeration system is in operation, the temperature expansion bag of the thermal expansion valve is responsive to the suction heat at the point on the suction pipe, and the opening degree of the automatic valve is adjusted so that the evaporating temperature can be automatically adjusted.

The empirical formula: Gg = 5400X + PXD2.8XL0.5

In this formula, Gg represents the system quality flow

P means pressure difference

D represents the inner diameter of the capillary

L stands for capillary length

3-4 capillary and filling amount matching

There are some relations between the actual capillary and the filling amount.

Refrigerant charge and suction pressure, exhaust pressure (capillary length)

(1) the refrigerant filling quantity increases, capillary suction constant, exhaust pressure will rise, power consumption increased, the superheat decreased, the undercooling increased.

(2) the same amount of refrigerant, capillary is increased, the suction pressure drop, exhaust pressure increases, the suction and exhaust temperature rise, power consumption increases, superheat rise, supercooling degree increased

毛细管长度计算(Capillary length calculation)