1、 What is a liquid separation head:

The liquid separation head is a key component used in refrigeration systems to evenly distribute refrigerant to multiple evaporator branches. The following is a detailed introduction to its structural principles, functions, and common types:

1.1 Structure and Principle:

The liquid separation head usually consists of an inlet and multiple outlets, and its internal structural design aims to evenly distribute the incoming refrigerant to each outlet branch. There are various common structures, such as using special splitter plates, guide vanes, or porous plates to guide the refrigerant to disperse evenly. The principle is to adjust and distribute the flow of refrigerant through these internal structures, so that the flow rate and pressure of refrigerant at each outlet are as equal as possible, in order to achieve uniform liquid separation.

1.2 Function

Uniform distribution of refrigerant: Ensure that the refrigerant can enter each evaporator branch evenly, so that each part of the evaporator can fully exert its refrigeration effect, improve the overall refrigeration efficiency of the evaporator, and avoid local overheating or undercooling caused by uneven liquid distribution.

Optimizing refrigeration system performance: enabling various components of the refrigeration system to operate stably under design conditions, reducing pressure fluctuations and uneven compressor loads caused by uneven refrigerant distribution, thereby extending the service life of each component in the system, reducing energy consumption, and improving the performance and stability of the entire refrigeration system.

1.3 Common Types

Straight tube liquid separation head: The structure is relatively simple, it is a straight tube with multiple evenly distributed small holes as outlets on the tube. The refrigerant enters from one end and is distributed to each branch through small holes. This type of liquid separation head is suitable for small refrigeration systems or situations where separation accuracy is not required.

T-shaped liquid separator: shaped like a "T", refrigerant enters from the vertical pipe of the "T" and is then distributed to different branches through multiple outlets on the horizontal pipe. The T-shaped liquid separation head has a relatively good separation effect and is commonly used in refrigeration systems that have certain requirements for liquid separation uniformity.

Multi channel splitter: It has multiple independent channels inside, and the refrigerant flows through these channels to different outlets after entering the splitter. This type of liquid separation head can achieve relatively accurate liquid separation and is suitable for large refrigeration systems or occasions that require high refrigeration accuracy, such as central air conditioning systems, large cold storage, etc.

2、 Reasons for uneven separation of liquid by the separation head

Uneven liquid separation in refrigeration systems is a common problem that can be caused by various reasons and can have adverse effects on the performance of the refrigeration system. The following is an analysis of the reasons for uneven liquid separation in refrigeration systems:

The design method of the liquid separation head (mainly the connection of the header or inlet channel pipeline) is unreasonable, resulting in uneven mixing of gas-liquid after separation;

Poor consistency in processing of liquid separation head products;

Liquid separation head welding blockage (which is commonly known in refrigeration systems);

The liquid separation head may be installed improperly and greatly affected by gravity;

The total length of each branch of the inlet and outlet condenser is different;

Whether the fluid flow is three-phase alternating current or multiphase flow will also affect the distribution diagram;

The local strong resistance of the branch road results in excessive losses;

Uneven wind force on each branch of the evaporator;

The second route of refrigerant is unreasonable and excessively affected by gravity;

The refrigeration system has good oil return, but the oil storage in each main road does not match.

2.1 Unreasonable design of the liquid separation head: If the structure and size of the liquid separation head are not designed properly, it will be difficult to ensure that the refrigerant is evenly distributed to each branch. For example, if the inlet flow rate of the separation head is too high or too low, it can lead to uneven separation. The inlet flow rate is too high, and the refrigerant stays in the separation head for too short a time, making it difficult to distribute evenly; If the inlet flow rate is too low, the refrigerant is prone to form local eddies in the separation head, which can also affect the separation effect.

2.2 Unreasonable pipeline layout: If the length, curvature, and direction of the pipeline connecting the liquid separation head and the evaporator are not consistent, it will cause different flow resistance of the refrigerant in each branch. For example, if some branch pipelines are longer and have more bends, while others are shorter and more straight, the refrigerant will tend to flow towards the short and straight pipeline branches with lower resistance, resulting in uneven liquid separation.

2.3 Changes in refrigerant state: If there is an imbalance between the gas-liquid phase before the refrigerant enters the separation head, it can also lead to uneven separation. For example, when refrigerant flows in a pipeline, due to pressure changes or pipeline heat dissipation, some liquids may vaporize prematurely, forming a gas-liquid mixture state. The distribution characteristics of gas-liquid mixtures in the separation head are different from those of pure liquids or gases, which can easily cause uneven distribution of gas and liquid phases in various branches.

2.4 Impurity blockage: Impurities in the refrigeration system, such as metal shavings, dust, oil stains, etc., may accumulate in the separation head or pipeline, hindering the normal flow of refrigerant and causing uneven separation. These impurities may be residual during the system installation process or may be caused by wear and tear of system components.

3、 The impact caused by uneven liquid separation

3.1 Decreased refrigeration effect: Uneven liquid separation can lead to uneven heat transfer in various parts of the evaporator, with some areas having good heat transfer while others have insufficient heat transfer, resulting in a decrease in the refrigeration efficiency of the entire evaporator and affecting the overall refrigeration effect of the refrigeration system.

3.2 Local icing of evaporator: In the case of uneven liquid separation, excessive refrigerant flow in some branches can cause the surface temperature of the evaporator in that part to be too low, resulting in icing. Freezing not only affects the heat transfer efficiency of the evaporator, but may also damage the evaporator components.

3.3 Uneven Compressor Load: Due to uneven liquid separation, the return air conditions of each evaporator branch are different, which can lead to unstable refrigerant flow and pressure absorbed by the compressor, resulting in uneven compressor load. Long term operation may shorten the service life of the compressor.

4、 Solution to uneven liquid separation-

4.1 Optimizing the design of the separation head: Select the appropriate type of separation head and optimize the structure and size of the separation head based on specific parameters of the refrigeration system, such as refrigerant flow rate, pressure, temperature, etc. For example, for large refrigeration systems, multi-stage liquid separation heads can be used to improve the uniformity of liquid separation.

4.2 Reasonable pipeline layout: Try to keep the length, curvature, and direction of the pipeline connecting the liquid separation head and evaporator consistent, reducing the difference in flow resistance between each branch. When arranging pipelines, sharp bends or excessively long straight sections should be avoided to ensure smooth flow of refrigerant inside the pipeline.

4.3 Ensure the stability of the refrigerant state: Before the refrigerant enters the separation head, a suitable gas-liquid separator or stabilizing device should be installed to ensure that the refrigerant enters the separation head in a stable gas-liquid two-phase state. At the same time, attention should be paid to insulation treatment of the refrigeration system pipelines to reduce the state changes of the refrigerant during the flow process.

4.4 Regular cleaning of the system: Before installing the refrigeration system, strict cleaning treatment should be carried out on the pipelines and equipment to remove impurities and oil stains. During the operation of the system, regular inspections and maintenance should be carried out to clean the impurities in the liquid separation head and pipeline, in order to prevent blockages. Filters can be installed to intercept impurities, and filter cartridges should be replaced regularly.