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5.5mm x 5.1mm id brass capillary tube

author:MF manufacturerstime:2022-03-14 09:36:33

Sand flow mechanism as a refrigeration system,Capillary is the simplest,Because of its low price、Flexible,Therefore, it is widely used in small refrigeration devices.,Recently, there is also use in larger refrigeration units.。But when using the capillary throttle,Pay attention to the selection of capillary lengths,According to this, we have organized some common atrial calculations.,I hope I can help everyone.。

5.5mm x 5.1mm id brass capillary tube

one、Capillary throttling characteristics

Capillary is a small aperture tube with a predetermined length,The inner diameter is generally known in the refrigeration system0.5~2mmabout,Length1~4mZi Steel tube within the range is capillary。It has no moving parts,A predetermined pressure drop can be generated in the refrigeration system,Generally used as a refrigerator、Flower elements of air conditioners and small cold storage。

The capillary generates pressure drop in length in the longitudinal direction according to its flow resistance.,To control the flow of the refrigerant and maintain the pressure difference of the condenser and evaporator。When there is a refrigerant having a deep cold, it enters the capillary,Pressure and state changes along the flow direction,First, the gradual decrease in the overcold liquid with the pressure.,First change to saturation liquid under corresponding pressure,This section is called liquid phase,Its pressure drop,And linear changes;From the beginning of the first bubble to the end of the capillary,Both are gas-liquid coexistence segments,Also known as two-phase flow segment,The saturated steam content in this segment gradually increases along the direction of flow.,Therefore, pressure drop is non-linear changes.,Caid to the end of the capillary,The pressure on the length of the unit is getting bigger。When the pressure is reduced to the saturation pressure at the corresponding temperature,It is necessary to generate flash phenomenon,Evaporate liquid itself,That is, as the pressure is lowered,The temperature of the refrigerant also decreases accordingly,Saturation temperature below the corresponding pressure。

After the inner diameter and length is determined,The flow of capillaries is mainly affected.、Export on both sides,High、Effect of pressure difference between low pressure,And the cooling of the refrigerant liquid、How much and tube bending、Circle number, etc.。Therefore, the unit system is time,Capillary that cannot be changed or replaced with arbitrary specifications。

According to relevant experiments,Under the same conditions and the same flow conditions,Length of capillary and its inner diameter4.6Secondary approximation,which is:



For capillary diameter,Mainly usedID:0.4—2.5mm,In some large systems,Will also useID6 Copper tube as a dispensing tube,Although considering the pressure drop of refrigerant in line,However, the throttle of such systems is mainly on the expansion valve,Only pressure loss can only be considered。

When the ambient temperature increases or the refrigerant is over from,Condensator pressure is high,Capillary flow rate increases the evaporator pressure and evaporation temperature。on the contrary,When the ambient temperature is lowered, the refrigerant is insufficient.,Condenser pressure becomes low,The reduction in capillary flow will reduce the pressure and evaporation temperature of the evaporator.,Result in a decrease in cooling capacity,Even the temperature required。 therefore,Cooling equipment with capillaries,It must be strictly controlled according to the design requirements.。

E.g200LLeft and right refrigerator plusR12Quantity150Left and right,The upper and lower deviation is not greater than5gram。The first filling of the general systemMCan be determined by the formula:

m=20+0.6V (gram)

In:V,Steamed coil content(cm3) Generally, the inner diameter of the refrigerator is0.5mm、length3mCopper hairy tube。 Generally, the inner diameter of the air conditioner is1.42mm、length450mmCopper hairy tube。 (Adjustment depending on the actual situation)

5.5mm x 5.1mm id brass capillary tube

two、Capillary general calculation

1、Experience formula

Calculation formula of capillary is not very accurate so far。Now introduces an empirical formula proposed from pipe resistance calculation。The rubber coefficients in the formula uses the Brandheishe,which is

5.5mm x 5.1mm id brass capillary tube

According to relevant reports,This formula calculates the length of the capillary as a composite coefficient.,More accessibility。The experience formula for capillary calculations is as follows:

5.5mm x 5.1mm id brass capillary tube

In -Pressure difference(Pk-Pe),Unit isPa

(5.5mm x 5.1mm id brass capillary tube)Re——Reynold number,

L——Capillary length,unitm

w——Refrigerant flow,unitm/s

(5.5mm x 5.1mm id brass capillary tube)ρ——Refrigerant density,unitkg/m3

d——Capillary inner diameter,unitm


Because the theoretical calculation of capillaries is complicated,Therefore, the method of selecting a capillary,Generally used calculation(Graphic)Precursively calculate the diameter and length of the capillary,Then use the experiment to verify the precise diameter and length.。And practical can also use a so-called subordinate。This is an empirical method,That is, refer to comparison of mature similar products to choose the desired capillary。A working condition that has the same or similar to the new product designed to the old product.,Then calculate the size of the capillary required for new products to calculate,Then use experiment to verify。General small system,Especially for home air conditioners, this method should be used.。

3、Computer Aided Design

View through related literature,As can be seen,The mathematical model of computer approach at home and abroad is similar.,The main difference is the selection of some formulas,One of the most important articles is as follows,I hope I can refer to the formula.,Write a utility of capillary calculations。Finally, it is corrected on the basis of the experiment.。 (Election《Refrigerator system capillary calculation model》,author:Zhao Xiaoyu、Korean gift bell、Zhu Mingkan。《Engineering thermal physics》,1995.5,This topic is the State Planning Commission“Eighth five”Key research project,In1994yearl0Establishment of thermodynamics and energy use academic conferences in China's Engineering Hot Physics Society held in Ningbo, Zhejiang Province)

5.5mm x 5.1mm id brass capillary tube