Test Harnesses

Parameterize and test a 4-way 3-position valve with a test harness. A plot script is provided with the example for comparing output flow between the block and data to verify the test harness. A live script is also provided with this example to explain the parameterization and the test harness workflow in detail.

Models a condenser or an evaporator in simple test setup with R134a refrigerant on the left side and moist air on the right side. It has a cross flow arrangement with the moist air blowing across tube banks filled with the refrigerant.

The actuator consists of a proportional 4-way directional valve driving a double-acting hydraulic cylinder. The cylinder drives a load consisting of a mass, viscous and Coulomb friction, constant force, and a spring. The actuator is powered by a variable-displacement, pressure-compensated pump, driven by a constant velocity motor. Pipelines between the valve, cylinder, pump, and the tank are simulated with the Hydraulic Pipeline blocks.

The 3-Zone Pipe (2P) block used to model vaporization or condensation of fluid flow in a pipe. The block divides the internal fluid volume into up to three zones: liquid zone, mixture zone, and vapor zone, depending on the state of the fluid along the pipe. As fluid flows through the pipe, heat is transferred between the environment external to the pipe and the fluid inside the pipe, causing it to change from liquid to mixture to vapor for the heating case or from vapor to mixture to liquid for the cooling case. The effect of thermal storage in the pipe wall can be optionally turned on by specifying a nonzero pipe wall thickness.

The Partially Filled Pipe (IL) block used to model the emptying and filling of a tank in multiple configurations. You can use the live script provided with this example to understand the effect of different configurations.

The liquid and vapor separation using the Receiver Accumulator (2P) block. The Receiver Accumulator (2P) block models a container of fluid in a two-phase fluid network with separate liquid and vapor ports. In an HVAC system, when this tank is placed between a condenser and an expansion valve, it acts as a receiver. Liquid connections to the block are made at ports AL and BL. When the tank is placed between an evaporator and a compressor, it acts as an accumulator. Vapor connections to the block are made at ports AV and BV. The fluid in the container can be fully liquid, fully vapor, or a mixture of both. Mass and energy exchange can occur between the fluid phases due to vaporization and condensation.

Model, parameterize, and test a counterbalance valve. When you run the model, it generates a plot of the flow from the load port to the back port due to the relief action of the counterbalance valve. A counterbalance valve allows an upstream flow from the back port to the load port through the check valve stage, and it allows a downstream flow from the load port to the back port through the relief stage. Counterbalance valves help with the load holding, load actuation speed control, and safety.

A test circuit built to check the characteristics of a pressure compensator. A pressure source is connected to two flow paths, each with a fixed orifice and a variable orifice that acts as a variable load. Along one flow path a pressure compensator is installed.

A test circuit built to check the characteristics of a pilot-operated check valve. The valve is loaded with three ideal pressure sources, two of which create pressure differential across the main flow line, while the third applies pressure to the pilot inlet X. The pilot pressure allows flow through the valve even if the main pressure differential is negative.

A test circuit built to check the pressure-flow characteristic of a direct-acting pressure-relief valve. The valve model consists of an orifice, a hydro-mechanical converter, a preloaded spring, and a hard stop.

The behavior of a flow divider subjected to varying loads. The model consists of a power unit, flow divider, and two consumers. The power unit is modeled using a flow rate source and a pressure relief valve. The Flow Divider block splits the flow between the two variable orifices.

A test rig for a gas-charged accumulator. The accumulator is charged by the pressure source while the orifice is closed, held at its charged pressure by the check valve, and discharged as the orifice opens.

A test rig for a spring-loaded accumulator. The accumulator is charged by the pressure source while the orifice is closed, held at its charged pressure by the check valve, and discharged as the orifice opens.

A test rig used to investigate the water hammer effect, which occurs when a variable orifice is abruptly shut off with full flow rate flowing through the branch. The water hammer behavior of the pipeline can be investigated by changing pipeline dimensions, number of segments in the pipeline model, fluid properties, valve closure speed, and minimum opening.

The behavior of a constant volume chamber exposed to a step increase in pressure. The chamber is placed between two linear hydraulic resistances and subjected to an abrupt change in supply pressure. The chamber is a piece of a steel cylindrical pipe of 0.03 m internal diameter, 0.036 m external diameter, and 16.5 m length. If the chamber wall is set to rigid and the amount of entrapped air is zero, the pressure change at the chamber inlet can be determined analytically.

Model, parameterize, and test a pressure reducing valve. The model is used to generate a plot of the regulation curve i.e. a plot of flow vs regulated pressure. This plot can be compared with the characteristics from the manufacturer datasheet to verify the test harness. The regulation curve displays two valve functions namely the reducing function and the relieving function. The reducing valve remains open when the pressure at the secondary port is less than a specified pressure, known as the set pressure. When the pressure at the secondary port meets or surpasses the set pressure, the reducing valve closes. In the regulation curve, the region of positive flow represents the phase when the reducing valve is open and gradually closes. The pressure reducing valve used in this example has a check valve that relieves pressure when the secondary pressure is about to surpass the set pressure. During this phase, the hydraulic fluid escapes via the check valve to the primary port keeping the secondary pressure constant at the set pressure. The region of negative flow in the regulation curve represents the phase when the pressure reducing valve is closed and the check valve opens gradually. Pressure reducing valves are used in industry to limit and maintain pressure during operations like hydraulic pressing, punching, drilling and stamping.

Read and format compressor map data for use with the Compressor (G) block. Open the livescript to see the full workflow.