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 for handling free-surface flows and moving parts within the domain and allows the simulation of any conceivable refrigerator geometry and operating mode, 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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