## 2 Experimental Set-Up and Test Methodology
### Test Methodology  
The systems were evaluated using 24-h energy consumption tests using a similar procedure as described by [PERSON] et al. [16]. The tests considered stable operation of the systems when the average product temperature inside the cabinet was of 2 \({}^{\circ}\)C. The energy evaluation was performed for three water dissipation temperatures in the condenser, they established using a constant dissipation water flow rate of 1 m\({}^{3}\).h\({}^{-1}\) and 23.3, 32.8 and 43.6 \({}^{\circ}\)C inlet temperatures, thus covering a wide range of operating conditions.  
To perform the test, the climatic chamber was maintained at 25 \({}^{\circ}\)C and 55% of relative humidity and the compressor was operated at its nominal speed (1450 rpm) using ON/OFF control strategy with the pressure switches of the plant. The pressure switches were adjusted to obtain a low-cut temperature of \(-25.0\)\({}^{\circ}\)C and a cut-in temperature of \(-4.5\)\({}^{\circ}\)C. Superheating degrees of the expansion valves were set at 5 K. For each test condition, the set point of the cabinet was adjusted to obtain an average product temperature of 2 \({}^{\circ}\)C (arithmetic mean of temperature of the five M-test packages). The cabinet set point temperature varied from 0.9 to 1.1 \({}^{\circ}\)C. Figure 3 illustrates the main operating temperatures for the direct expansion configuration using R-134a at an inlet water temperature to the condenser of 43.6 \({}^{\circ}\)C, and Figure 4 for the equivalent in the indirect arrangement. Operation of the compressor, described using black dots in Figures 3 and 4, is as follows: at point (1), the expansion valve of the cabinet opens to fill the evaporator with refrigerant (the cabinet air inner temperature has reached set point temperature +1 K). At point (2), low pressure reaches cut-in temperature (\(-4.5\)\({}^{\circ}\)C, 2.48 bar for R-134a) and activates the compressor. At point (3), the expansion valve of the cabinet closes (the cabinet air inner temperature has reached set point temperature \(-1\) K). At point (4), low pressure reaches cut-off temperature (\(-25\)\({}^{\circ}\)C, 1.06 bar for R-134a). With direct expansion, the compressor starts only once in each period; however, with indirect configuration the compressor starts two additional times in each period, because the volume of the suction is short (see Section 4). Defrosting of the cabinet's evaporator has been highlighted with two white dots, at the start and end of the period. Defrosting is set every eight hours, so it is randomly associated with the behaviour of the plant. However, it always ends when the air impulsion temperature (the air at the exit of the evaporator) reaches 5 \({}^{\circ}\)C.  
The order of the tests was: first, direct expansion with R-134a and then with R-507A, followed by indirect configuration, first with R-134a and then with R-507A. For the evaluation only Temper \(-20\)\({}^{\copyright}\) was used as a secondary fluid, since it offers better performance than other fluids, as presented by [PERSON] et al. [16].  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Temperature** & **Pressure** & \begin{tabular}{c} **Mass** \\ **Flow Rate** \\ \end{tabular} & \begin{tabular}{c} **Volumetric** \\ **Flow Rate** \\ \end{tabular} & \begin{tabular}{c} **Power** \\ **Consumption** \\ \end{tabular} & \
\begin{tabular}{c} **Relative** \\ **Humidity** \\ \end{tabular} &
\begin{tabular}{c} **Test** \\ **Package** \\ \end{tabular} \\ \hline DX refrigeration cycle & 8 & 3 & 1 & 1 & 1 & - & - \\ DX Cabinet & 4 & 2 & - & - & 1 & 1 & 5 \\ SF refrigeration cycle & 10 & 3 & 1 & 2 & 2 & - & - \\ SF Cabinet & 4 & - & - & - & 1 & 1 & 5 \\ Climatic chamber & 1 & - & - & - & - & 1 & - \\ Others & 1 & - & - & - & - & - & - \\ Uncertainty & \(\pm 0.5\) K & \(\pm 0.3\%\) & \(\pm 0.1\%\) & \(\pm 0.33\%\) & \(\pm 0.5\%\) & \(\pm 2\%\) & \(\pm 0.5\) K \\ \hline \hline \end{tabular}
\end{table}
Table 2: Number of sensor elements and uncertainties.