Polyurethane simulation during the PUR foaming process in a fridge can be performed with our CFD simulation 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.
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
polyurethane (PUR) injection by one or more inlets,
moving parts and inlets,
free definable PUR properties by equations or curves and
large refrigerator geometries with small gaps or cutouts.
NOGRID's particular strengths are the rapid preprocessing (no grid needs to be generated) and the outstandingly short computation time even for complicated cavities with very small ducts.
Three possible types of production
The left example shows a refrigerator where the PU 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. In the middle example the fluid is injected by a pipe which moves outwards during the filling process. In the right example the simulation starts with PUR liquid inside an open cavity. The cavity closes and presses the foaming liquid into the refrigerator wall.
Figure 1: Simulation of PUR foaming in a fridge - injection by two fixed inlets (left), injection by a moving pipe (middle) and PUR distribution by a closing cavity; computed with NOGRID points Click on the animations to see high quality videos.
Identification air entrapment
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 2. The PUR enters the gaps from both sides, resulting in an entrapment of air. A solution would be ventilation holes or different inlet positions.
Figure 2: Velocity field and free surface flow near cooling cutouts, computed with NOGRID points The simulation shows that this position is at risk for an air entrapment.
Did you know,
that numerical simulation is not only used to understand processes or to optimize a process,
but also to control the process development in terms of quality (Two-man rule)?
Did you know,
that numerical simulation helps to give your project a structure and to establish a very useful documentation system?
Did you know,
that numerical simulation helps to train your employees and to increase the knowledge about your procedures and processes?