Simulation of three Refrigerator PUR Filling and Foaming Processes

Animation PUR refrigerator pressing filling type in NOGRID points CFD software

Figure 1: PUR refrigerator: Filling process is a mixure of initial pressing and foaming

Animation refrigerator PUR foaming with needle as injector in NOGRID points CFD software

Figure 2: Refrigerator foaming with moving needle as injector

Fridge PUR foaming: filling with two inlets, computed with NOGRID points CFD software

Figure 3: Refrigerator PUR foam filling with two inlets

Refrigerator air bubbles generation, computed with NOGRID points CFD software

Figure 4: Air entrapment generation, velocity field and free surface flow near cooling cutouts, computed with NOGRID points

In this case study we present the simulation of three possible refrigerator PUR filling and foaming processes (injection types), although not all of them are currently in productive use:

In the left top example (Figure 1) the simulation begins with PUR liquid inside an open cavity. The cavity then closes, pressing the foaming liquid into the refrigerator wall.
In the middle example (Figure 2) the fluid is injected through a pipe which moves outwards during the filling process.
The left bottom example (Figure 3) shows a refrigerator where the PUR is injected via two inlets located at the lower side. The foaming process starts as soon as the PUR enters the cavity, and the filling is completed after two seconds.

Air entrapment increases the heat conductivity of the thermal insulation and should be avoided. CFD simulations can help identify critical locations. In our simulation, the cooling cutouts on the lower left side of the refrigerator (see Figure 4) are identified as potential air entrapment zones. The PUR enters these gaps from both sides, resulting in an entrapment of air. Possible solutions include adding ventilation holes or changing the inlet positions.

PUR (polyurethane) foam-fill simulation in a refrigerator can be accurately performed using the CFD software NOGRID points. By using polyurethane foams, a good thermal insulation can be achieved. The most efficient way to insulate a refrigerator is to inject PUR directly into the hollow walls. The foaming process takes place in the cavity and fills it completely.

Simulate any conceivable refrigerator geometry

NOGRID points can help to understand the flow inside the cavity. It can visualize air entrapment, the density distribution of the insulation material, and the pressure exerted by the PUR foam on the cavity walls. NOGRID combines powerful capabilities to handle free-surface flows and moving parts within the domain and allows the simulation of any conceivable refrigerator geometry and operating mode, such as

fully 3D computation solving the complete Navier-Stokes equations
easy and intuitive setup of the FSI (Fluid-Structure-Interaction) case
freely definable PUR material properties by equations or curves
polyurethane (PUR) injection by one or more inlets
open or closed domains including moving of additional parts
moving of the mixing head

Whitepaper PUR Foaming

Why choose Nogrid?

NOGRID provides professional CFD software for the simulation of fluid flow, heat and mass transfer, and chemical reactions. Its efficient modelling workflow helps engineers analyse flow behaviour, evaluate designs and make informed decisions without creating a conventional volume mesh.

Faster model preparation

With NOGRID, only the geometry boundary needs to be meshed. The finite points inside the fluid domain are generated automatically according to user-defined settings, both at the start of the simulation and during the calculation.

This approach reduces preprocessing effort and makes it easier to prepare complex geometries and cavities for simulation.

Efficient CFD workflow

The modelling process follows four straightforward steps:

Build the geometry. Mesh the boundary. Define the simulation. Start the calculation.

NOGRID is designed to provide short computation times, including for applications involving complex cavities. Engineers can use the resulting data to examine flow distribution and other relevant flow characteristics.

Better insight into fluid-flow processes

CFD solves the fundamental equations governing fluid flow. NOGRID software enables engineers to predict and analyse the behaviour of fluids and related physical processes before or alongside physical testing.

The simulation results can support:

evaluation and comparison of design alternatives
optimisation of construction and operating parameters
improved planning reliability
reduction of development time and testing effort
faster progression from design to market or operation

Steps from geometry generation to simulation results

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When internal time, expertise or resources are limited, NOGRID can support your project with individual numerical simulation services. Our engineers develop and evaluate CFD models based on the specific requirements of your application.