Model selection method for liquid distribution pipes in refrigerating system of rail air conditioner

Abstract

A liquid distribution pipe type selection method in a track air conditioner refrigeration system belongs to the technical field of refrigeration, and comprises the following steps: S10, determining the refrigerant type, the refrigerant liquid temperature before throttling, the refrigerant evaporation temperature, the number of liquid distribution pipes, the minimum length of the liquid distribution pipes and the design refrigerating capacity of an evaporator in the track air conditioner refrigeration system; s20, the length and the pipe diameter specification of the liquid separation pipe are primarily selected; s30, the refrigerating capacity of a single liquid distribution pipe and the load proportion of the refrigerating capacity of the single liquid distribution pipe are calculated; s40, if the proportion of the refrigerating capacity load of the liquid distribution pipe is not within the range of 80%-100%, the pipe diameter specification of the liquid distribution pipe is adjusted, the step S30 is executed, and if the proportion of the refrigerating capacity load of the liquid distribution pipe is within the range of 80%-100%, the step S50 is executed; and S50, if the proportion of the refrigerating capacity load of the liquid distribution pipe is not within the range of 85%-95%, the length of the liquid distribution pipe is adjusted, the step S30 is executed again, and if the proportion of the refrigerating capacity load of the liquid distribution pipe is within the range of 85%-95%, the model change and selection of the liquid distribution pipe are finished. The refrigerating capacity load proportion and the pressure drop of the liquid distribution pipe are effectively improved, and the refrigerating capacity and the energy efficiency ratio are both improved.

Description

Technical Field

[0001] This invention belongs to the field of refrigeration technology, specifically relating to a method for selecting a liquid distribution pipe in a rail air conditioning refrigeration system. Background Technology

[0002] The distributor pipe of an air conditioning unit in rail transit vehicles is located between the distributor and the evaporator. Because the distributor pipe is not one of the four major components of the refrigeration system, its design calculations are often neglected during the refrigeration system design process. Currently, air conditioning systems select distributor pipes of any appropriate length based on the distance between the distributor and the evaporator. When a large number of distributor pipes are used, 3 / 16-inch (4.76 mm) pipes are often chosen for ease of bending. Current practices do not consider distributor pipe design and do not assess the rationality of the selected pipe size. A distributor pipe with a small diameter and long pipe has a large refrigerant pressure drop, making flashing within the pipe more likely. A distributor pipe with a large diameter and short pipe has a small refrigerant pressure drop, which cannot guarantee the refrigerant's full development within the distributor pipe after passing through the distributor, affecting the uniformity of refrigerant distribution. Both refrigerant flashing within the distributor pipe and uneven refrigerant distribution result in a loss of air conditioning cooling capacity. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for selecting a liquid distribution pipe in a rail air conditioning refrigeration system. By improving the selection method as a whole, the appropriate pipe diameter and length of the liquid distribution pipe can be determined, which can effectively improve the cooling load ratio and pressure drop of the liquid distribution pipe, and improve both the cooling capacity and energy efficiency ratio.

[0004] The technical solution adopted in this invention is: a method for selecting a liquid distribution pipe in a rail air conditioning refrigeration system, the method comprising the following steps: S10. Determining the refrigerant type and the refrigerant liquid temperature T before throttling in the rail air conditioning refrigeration system. L Refrigerant evaporation temperature T e Number of separatory tubes N, minimum length of separatory tube L min S20. Initially select the length L and diameter d of the liquid distributor; S30. Calculate the cooling capacity and load percentage of a single liquid distributor; S40. If the load percentage of the liquid distributor is not within the range of 80%-100%, adjust the diameter of the liquid distributor and return to step S30. If the load percentage of the liquid distributor is within the range of 80%-100%, proceed to step S50. S50. If the cooling load ratio of the distributor is not within the range of 85%-95%, adjust the length of the distributor and return to step S30. If the cooling load ratio of the distributor is within the range of 85%-95%, the distributor replacement is completed.

[0005] The beneficial effects of this invention are as follows: by improving the selection method as a whole, the appropriate pipe diameter and length of the distributor can be determined, effectively improving the cooling load ratio and pressure drop of the distributor, and both the cooling capacity and energy efficiency ratio are improved; this invention can effectively solve and avoid the risk of flashing of refrigerant in the distributor and the reduction of cooling capacity caused by insufficient development. Attached Figure Description

[0006] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0007] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0008] See appendix Figure 1 This invention provides a method for selecting a liquid distribution pipe in a rail air conditioning refrigeration system, the method comprising the following steps: S10. Determine the refrigerant type and refrigerant liquid temperature T before throttling in the track air conditioning refrigeration system. L Refrigerant evaporation temperature T e Number of separatory tubes N, minimum length of separatory tube L min The design cooling capacity of the evaporator is Q; Prerequisites: Complete the refrigeration system calculations for the air conditioning unit under design conditions, and determine the selection and design of the three main components: compressor, evaporator, and condenser. Use the refrigerant liquid temperature T before throttling from the air conditioning unit refrigeration system calculation results. L and evaporation temperature T e The number of flow paths in the evaporator is equal to the number of distribution pipes, N. The design cooling capacity Q of the evaporator divided by the number of distribution pipes N gives the cooling load Q of a single distribution pipe. l .

[0009] S20. Initial selection of the length L and diameter d of the separatory tube; S30. Calculate the cooling capacity of a single distributor pipe and the cooling capacity load ratio of a single distributor pipe; calculate the cooling capacity and cooling capacity load ratio of the distributor pipe according to empirical formulas, and determine whether the distributor pipe design is reasonable based on the calculation results.

[0010] S40. If the cooling load of the distributor is not within the range of 50%-100%, adjust the pipe diameter of the distributor and return to step S30. If the cooling load of the distributor is within the range of 50%-100%, proceed to step S50. S50. If the cooling load ratio of the distributor is not within the range of 80%-95%, adjust the length of the distributor and return to step S30. If the cooling load ratio of the distributor is within the range of 80%-95%, the distributor replacement is completed.

[0011] In step S10, the minimum length of the separator tube is determined by the spatial distance between the separator and the evaporator inlet.

[0012] The refrigerant types include R134a, R407C, and R410A. Commonly used zero ODP (Ozone Depletion Potential) refrigerants are R134a, R407C, and R410A. In step S10, the diameter of the dispensing tube includes 6.35mm, 6mm, and 4.76mm; the material of the dispensing tube is copper, and the commonly used diameters are 1 / 4 inch (6.35mm), 6mm, or 3 / 16 inch (4.76mm). One of the commonly used diameters of 1 / 4 inch (6.35mm), 6mm, and 3 / 16 inch (4.76mm) is selected.

[0013] The initial selection method for the length of the separatory tube is as follows: Add the minimum length L of the separatory tube to the minimum length of the separatory tube. min 10%. The minimum length L of the separator tube is determined based on the spatial distance between the separator and the evaporator inlet. min The length L of the separator should be greater than the minimum length L. min This ensures smooth pipe connections.

[0014] In step S30, the cooling capacity Q of a single liquid distribution pipe d The empirical formula is: , In the formula, e represents the natural logarithm, and the parameters of A1-A6 are determined by the following table: .

[0015] Based on the type of refrigerant used in the air conditioning unit, parameters from A1 to A6 are substituted into the empirical formula for calculating the cooling capacity under the design conditions of the liquid separator. T L T e Substitute L and d into the empirical formula for cooling capacity under the design conditions of a single distributor pipe and calculate the cooling capacity Q under the design conditions of a single distributor pipe. d .

[0016] The formula for the cooling load ratio R of a single liquid distribution pipe in step S30 is: , In the formula, Q l The cooling load of a single distributor pipe is expressed by the formula: Q l =Q / N.

[0017] The method for adjusting the length of the separatory tube in step S50 is as follows: Each adjustment increases the minimum length of the separator tube by L based on the original length L. min 15%.

[0018] After the separator tube selection is completed in step S50, the separator tube length L needs to be corrected. The correction principle is as follows: if the tens or units digit of the separator tube length L is greater than 0, it needs to be discarded, and then the hundreds or tens digit is rounded up by 1. For example: if L=450, the correction value of L is 500; if L=78, the correction value of L is 80.

[0019] By calculating the cooling load ratio and pressure drop of the distributor, the specifications and length of the distributor are rationally selected. This standardizes the design of the distributor in rail transit air conditioning refrigeration piping, avoiding the risks of refrigerant flashover and insufficient development leading to reduced cooling capacity, and improving the cooling capacity and energy efficiency ratio of the refrigeration system. After designing according to the method of this application, the cooling load ratio and pressure drop of the distributor are improved, and the measured cooling capacity and energy efficiency ratio are both improved.

[0020] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for selecting a liquid distribution pipe in a rail-mounted air conditioning refrigeration system, characterized in that, The method includes the following steps: S10. Determine the refrigerant type and refrigerant liquid temperature T before throttling in the track air conditioning refrigeration system. L Refrigerant evaporation temperature T e Number of separatory tubes N, minimum length of separatory tube L min The design cooling capacity of the evaporator is Q; S20. Initial selection of the length L and diameter d of the separatory tube; S30. Calculate the cooling capacity of a single distributor pipe and the load percentage of the cooling capacity of a single distributor pipe; S40. If the cooling load of the distributor is not within the range of 50%-100%, adjust the pipe diameter of the distributor and return to step S30. If the cooling load of the distributor is within the range of 50%-100%, proceed to step S50. S50. If the cooling load ratio of the distributor is not within the range of 80%-95%, adjust the length of the distributor and return to step S30. If the cooling load ratio of the distributor is within the range of 80%-95%, the distributor replacement is completed.

2. The method for selecting a separatory tube according to claim 1, characterized in that, In step S10, the minimum length L of the separator tube min It is determined by the spatial distance between the distributor and the evaporator inlet.

3. The method for selecting a separatory tube according to claim 1, characterized in that, The refrigerant types include R134a, R407C, and R410A.

4. The method for selecting a separatory tube according to claim 1, characterized in that, The diameter d of the separator in step S10 includes 6.35mm, 6mm, and 4.76mm; The initial selection method for the length of the separatory tube is as follows: Based on the minimum length L of the separatory tube... min Based on the minimum length L of the separator tube min 10%.

5. The method for selecting a separatory tube according to claim 1, characterized in that, In step S30, the cooling capacity Q of a single liquid distribution pipe d The empirical formula is: ， In the formula, e represents the natural logarithm, and the parameters of A1-A6 are determined by the following table: 。 6. The method for selecting a separatory tube according to claim 1, characterized in that, The formula for the cooling load ratio R of a single liquid distribution pipe in step S30 is: ， In the formula, Q l The cooling load of a single distributor pipe is expressed by the formula: Q l =Q / N.

7. The method for selecting a separatory tube according to claim 1, characterized in that, The method for adjusting the length of the separatory tube in step S50 is as follows: Each adjustment increases the minimum length of the separator tube by L based on the original length L. min 15%.

8. The method for selecting a separatory tube according to claim 1, characterized in that, After the selection of the separator tube in step S50 is completed, the length L of the separator tube also needs to be corrected. The correction principle is as follows: The value of the length L of the separatory tube. If the tens or units digit of L is greater than 0, it should be discarded, and then the hundreds or tens digit should be rounded up by 1.

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