1. Water inlet pipe of main circulation loop (low pressure suction pipe)

Function: deliver the low-temperature coolant from the radiator, expansion tank or low-temperature loop to the inlet of the circulating pump, so as to ensure that the pump body can efficiently suck in the cooling medium.

Typical configuration:

The pipeline interface is located at the front or bottom of the circulating pump and connected with the radiator downcomer, the liquid outlet of the expansion tank or the outlet of the heat exchanger.

Large diameter design (usually ≥25mm) is adopted to reduce the flow resistance and avoid the risk of cavitation.

The material should have the characteristics of low temperature deformation resistance (such as EPDM rubber or silica gel), and the inside contains a reinforced fiber layer to resist negative pressure deformation.

2. Water outlet pipe of main circulation loop (high pressure output pipeline)

Function: Deliver the pressurized coolant to the engine block, battery pack or motor and other heat source components to realize active heat dissipation.

Design points:

The coolant distribution manifold, which directly connects the outlet of the circulating pump with the heat source components, bears the working pressure of the system (1.5~2.5 bar for the traditional engine system and 3~5 bar for the new energy high-pressure system).

The pipeline in high temperature section adopts metal-rubber composite structure (such as aluminum hard pipe+silicone hose), or all silicone hose is equipped with heat insulation sheath.

The layout needs to optimize the flow direction, reduce the bending angle and avoid the energy loss caused by turbulence.

3. Small circulation bypass pipeline

Function: under cold start or low load condition of heat source, establish short path circulation, accelerate system preheating and reduce heat loss.

Working logic:

The bypass pipeline connects the outlet of the circulating pump with the thermostat or thermal management module, bypassing the radiator and directly flowing back to the pump body.

Integrate current limiting valve or electronic control valve, dynamically adjust bypass flow according to temperature signal, and balance warm-up speed and heat dissipation demand.

4. Branch pipeline of heat exchanger

Application scenario: In hybrid or pure electric vehicles, the circulating pump may provide cooling liquid for battery cooler, motor inverter liquid cooling plate or air conditioning system condenser.

Structural features:

The pipeline branches from the main circulation loop and is driven by a three-way valve or an independent pump body to form a multi-stage heat dissipation network.

Adopt quick plug connector and lightweight nylon tube (such as PA12) to adapt to compact space layout and high-frequency vibration environment.

Some high-voltage systems are equipped with double-layer pipe wall structure, and the inner conductive layer is used for leakage monitoring.

5. Expansion compensation pipeline

Function: Connect the water inlet pipe of the circulating pump with the expansion water tank, balance the pressure fluctuation of the system and compensate the change of coolant volume.

Technical details:

The pipeline is usually a small diameter hose (8~12mm in diameter), which extends from the bottom of the expansion tank to the inlet of the circulating pump.

Integrated one-way valve or breathable film to ensure that the gas is exhausted and the coolant does not flow backwards.

In new energy vehicles, the pipeline may be extended to an intelligent compensation system with electronic liquid level sensor.

6. Redundant cooling pipeline (high performance/high reliability system)

Special design: In racing cars or high-load commercial vehicles, the circulating pump may be equipped with parallel standby pipelines to realize fault tolerance by switching valves.

Implementation mode:

Double-pump series or parallel structure, with independent water inlet and outlet pipes, ensures that the basic cooling function can still be maintained under a single fault.

The pipeline is made of high explosive pressure material (such as PTFE lined stainless steel braided layer), which can withstand extreme temperature and mechanical stress.

Technical specifications and maintenance requirements

Pressure tolerance: the pipeline shall meet the ISO 11425 standard, the bursting pressure shall be ≥6× working pressure, and the pulse fatigue life shall be > 500,000 times.

Thermal aging performance: it keeps elasticity in the range of -40℃~180℃, and the high temperature (sensitive word, shielded) product expansion rate is less than 5%.

Failure prevention: regularly check the O-ring tightness, clamp torque value (usually 2 ~ 4 N m) and surface aging cracks of pipeline joints.

Upgrade plan: track or modified vehicles can be replaced with all-aluminum hard pipes or aviation-grade silicone pipes to improve heat dissipation efficiency and reliability.