Simulation of three Refrigerator PUR Filling and Foaming Processes

Animation PUR refrigerator pressing filling type in NOGRID points 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 software

Figure 2: Refrigerator foaming with moving needle as injector

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

Figure 3: Refrigerator PUR foam filling with two inlets

Refrigerator air bubbles generation, computed with NOGRID points 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), even if not all are in productive use:
In the left top example (figure 1) the simulation starts with PUR liquid inside an open cavity. The cavity closes and presses the foaming liquid into the refrigerator wall.
In the middle example the fluid is injected by a pipe which moves outwards during the filling process.
The left bottom example shows a refrigerator where the PUR is injected using two inlets at the lower side. The foaming process starts when the PUR enters the cavity, the filling is done after two seconds.

Air entrapment increases the heat conductivity of the thermal isolation and must be avoided. CFD simulations can reveal critical positions. In our simulation the cooling cutouts on the lower left side of the refrigerator are at risk for an entrapment, see figure 4. The PUR enters the gaps from both sides, resulting in an entrapment of air. Solutions could be ventilation holes or different inlet positions. The simulation shows that this position is at risk for an air entrapment.

PUR (Polyurethane) foam-fill simulation in a refrigerator (or fridge) can perfectly be performed with CFD software NOGRID points. By using polyurethane foams a good thermal isolation can be achieved. The most efficient way to produce a thermal isolation of a refrigerator is the injection of PUR directly into the hollow wall. The foaming 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 show the entrapment of air, the density distribution of the isolation material, and the pressure of the PUR foam acting on the cavity. NOGRID unites abilities to handle free surface flow and moving parts in the domain and allows the simulation of any conceivable refrigerator geometry and operation modes such as

computation is in full 3D solving complete Navier-Stokes-Equations
easy and intuitive setup of the FSI (Fluid-Structure-Interaction) case
free 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

Nogrid's strengths

Particular strengths of NOGRID's fluid flow CFD software are the rapid preprocessing (no fluid grid needs to be generated, only the boundary mesh, inner finite points are generated automatically depending on User setting initially and during computation), and the outstandingly short computation time even for complicated cavities.

As you can see in the image below, the boundary of the geometry still requires a mesh to allow the interior finite points to detect the boundary. The boundary must therefore be meshed and the finite points inside are automatically generated during the simulation controlled by User specifications.

Easy and fast modelling: Build geometry, mesh boundary, setup the case and start computation

What is CFD from NOGRID?

CFD solves the fundamental equations that define the fluid flow process. With CFD software from NOGRID every engineer makes better decisions by predicting, analyzing and controlling fluid flow, heat and mass transfer or chemical reaction. By using NOGRID software for flow modeling you receive information on essential flow characteristics as for example flow distribution. Using it additional to testing and experimentation NOGRID software helps to improve the evaluation of your design – resulting in better construction and operation parameters, increasing planning security and money savings due to faster time to the marketplace for your product or process.

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