Material Flow

“Material Flow” or Advection

Thermal Desktop® is very capable of modeling steady and unsteady heat transfer problems including conduction, convection, thermal radiation, etc. for moving and stationary parts.

When a batch process is to be simulated, or when discrete parts move (such as ingots through a furnace, or ground-tracking antennae on satellites), the part itself can be translated or rotated within a transient solution. But when the motion is continuous, such that a steady-state solution is possible, different modeling methods are available and should be employed.

Examples of such continuous motion include a sheet of glass solidifying as it is lowered through a temperature-controlled zone, a gypsum board moving through a drier, and a conveyor belt carrying baked goods through a continuous oven. In those circumstances, a fixed model of the both stationary parts (heat lamps, ovens, driers, etc.) and the moving parts (rollers, sheets, belts, etc.) is built. Then, an advection or “material flow” term is superimposed on the rotating or translating parts.

For example, below is an open mesh conveyor belt with rollers moving under a heat lamp (more like a laser: collimated). Ray plots have been superimposed to show the lamp rays passing through the mesh belt.

Conveyor with radiation and advection

Example applications for this capability include:

  • Belt conveyor furnaces, conveyor ovens
  • Steel and aluminum sheet metal manufacturing
  • Glass making (especially plate glass)
  • Paper making, fiber products, particle board and flakeboard drying and curing, drywall (wallboard) manufacturing
  • Optical fiber manufacturing (drawing fiber optic cable through a furnace)
  • Pebble bed reactors
  • Coke furnaces
  • Rotary furnaces
  • Carbon foam and metal foam heat exchangers, geothermal storage systems
  • Rotating disk heat exchangers and dehumidifiers
  • Moving belt heat exchangers, moving belt radiators

Hot Wire: Material Flow Example

A large rectangular copper “wire” passes through a continuous-flow tubular furnace used to harden a thermoset polymer coating. A pair of cooled rollers at the exit of the furnace help to both position the wire and smooth the coating.

Bar through oven

Advection model results

Advection model results roller detail

Advection model coating temperatures

 

dispersed vs. coalesced front

Tuesday, June 26, 2018, 1-2pm PT, 4-5pm ET

This webinar describes flat-front modeling, including where it is useful and how it works. A flat-front assumption is a specialized two-phase flow method that is particularly useful in the priming (filling or re-filling with liquid) of gas-filled or evacuated lines. It also finds use in simulating the gas purging of liquid-filled lines, and in modeling vertical large-diameter piping.

Prerequisites: It is helpful to have a background in two-phase flow, and to have some previous experience with FloCAD Pipes.

Register here for this webinar

FloCAD model of a loop heat pipe

Since a significant portion of LHPs consists of simple tubing, they are more flexible and easier to integrate into thermal structures than their traditional linear cousins: constant conductance and variable conductance heat pipes (CCHPs, VCHPs). LHPs are also less constrained by orientation and able to transport more power. LHPs have been used successfully in many applications, and have become a proven tool for spacecraft thermal control systems.

However, LHPs are not simple, neither in the details of their evaporator and compensation chamber (CC) structures nor in their surprising range of behaviors. Furthermore, there are uncertainties in their performance that must be treated with safety factors and bracketing methods for design verification.

Fortunately, some of the authors of CRTech fluid analysis tools also happened to have been involved in the early days of LHP technology development, so it is no accident that Thermal Desktop ("TD") and FloCAD have the unique capabilities necessary to model LHPs. Some features are useful at a system level analysis (including preliminary design), and others are necessary to achieve a detailed level of simulation (transients, off-design, condenser gradients).

CRTech is offering a four-part webinar series on LHPs and approaches to modeling them. Each webinar is designed to be attended in the order they were presented. While the first webinar presumes little knowledge of LHPs or their analysis, for the last three webinars you are presumed to have a basic knowledge TD/FloCAD two-phase modeling.

Part 1 provides an overview of LHP operation and unique characteristics
Part 2 introduces system-level modeling of LHPs using TD/FloCAD.
Part 3 covers an important aspect of getting the right answers: back-conduction and core state variability.
Part 4 covers detailed modeling of LHPs in TD/FloCAD such that transient operations such as start-up, gravity assist, and thermostatic control can be simulated.