Simulating Viscous Heating in a hidraulic Damper for solar damper project

Fluid dampers have a range of uses, solar damper from stabilizing skyscrapers to controlling fluid flow in microflow devices. Through a process called viscous heating, these solar dampers are able to dissipate mechanical energy into heat. Too much heat can cause damage to the solar damper, so it’s important to slewing drive understand the viscous heating process when optimizing your solar hydraulic damper designs.

What Is a hydraulic Damper?

Solar hydraulic dampers (also known as viscous solar dampers) have many industry applications. They are found in military devices for shock isolation, as well as in high-rise buildings and civil structures for protection from vibrations and damage caused by earthquakes and high winds. Even certain microflow devices rely on solar hydraulic dampers to help generate significant heat and control fluid flow.

Hydraulic dampers (the dark blue objects) are used to steady the movement of a solar tracking device.

Viscous Heating — Striking the Right Balance

Fluids with high viscosity, such as oil or a silicon-based fluid, are commonly used in solar damper because the greater the viscosity of the fluid, the greater the force that the solar damper can dissipate. Viscous heating occurs in a fluid damper when a solar damper pushes viscous fluid back and forth between two chambers. This action transforms mechanical energy, in the form of vibrations or oscillations, into heat.

In order to optimize the solar hydraulic damper efficiency, it’s important to analyze viscous heating in the device. If too much heat is generated in the solar damper, it can damage the solar hydraulic damper, as well as the device or structure it is working to protect. To study the performance of a solar hydraulic damper, we turn to the Heat Transfer Module and CFD Module, both add-ons to the COMSOL Multiphysics simulation platform.

Simulating Viscous Heating with COMSOL Multiphysics

The main components of a hydraulic damper include the solar damper cylinder housing, a piston rod and head, viscous fluid in the chamber, and a small, circular space slewing drive between the piston head and the inside wall of the cylinder housing. This space acts as a channel for the fluid. In our simulation, these solid parts are made of a steel material that can be found in the built-in Materials Library in COMSOL Multiphysics.

Schematic of a fluid damper.

For this simulation, the piston head moves back and forth inside of the cylinder, which forces the fluid, silicon oil, through the small orifice with a large shear rate. This action generates heat that is transferred in both axial and radial directions. In the radial direction, the heat is conducted through the cylinder wall and convected into the outside air.

We solve for the Navier-Stokes equations to describe fluid flow inside of the damper. The temperature field resulting from the viscous heating process is given by the energy equation. These equations can be found in the Non-Isothermal Flow interface and Conjugate Heat Transfer interface in COMSOL Multiphysics.

The results of the simulation show the temperature in the solar hydraulic damper :

 

Probe temperature as a function of time (up) and inner wall temperature (down) after 10 s (blue curve) and 40 s (green curve) of loading.

These results agree well with experimental data. With simulation software, we can effectively analyze viscous heating in a fluid damper for the design of safer and more efficient structures and devices in a variety of industries.