4.3.3. Boundary conditions for heat flow rate

The boundary conditions for the heat flow rate take into account the conductive heat transfer through the cabinet walls and the heat generated by the illumination system of the display case.

The conductive heat transfer was defined using Fourier's law; the overall heat transfer coefficient was calculated based on the thermal conductivity of each individual layer of the respective wall. The conductive heat transfer rates were as follows: 6 W/m<sup>2</sup> for the ceiling of the cabinet; 7 W/m<sup>2</sup> for the bottom of the cabinet; and 7.63 W/m<sup>2</sup> for the side walls.

Fluorescent lamps, type OSRAM L58W20, were used for the illumination of the appliance; the corresponding heat flow rate was 10 W/m<sup>2</sup> .

## 4.3.4. Boundary conditions for the walls

The cabinet walls were modeled only in the wall-air contact areas. The average temperatures were obtained experimentally, as follows: evaporator fins—0.95C; interior walls +7C; shelves +5C.

### 4.3.5. Product thermal load

4.3.2. Boundary conditions for GRA

Figure 25. Air temperature at the GPA level.

64 Refrigeration

turbulence parameters were defined as above.

Figure 26. Air velocity profiles, after filtering, for the three vertical planes.

The boundary conditions for the base grill take into account the average experimental values: over the entire length of the grill, air velocity is 1.7 m/s, and air temperature is +9.2C. The air According to the EN-ISO 23953 standard, the load is simulated using a gel-type substance (tylose), with thermal properties similar to the ones of beef meat. However, in the present simulation, there was no product load inside the cabinet.
