## 4 Charging Test and Litchi Spray Precooling Tests
### Evaluation of Spray Hydrocooler Performance  
The water temperature (\(T_{mat}\)) was measured at three different layers (upper, middle, and lower) in the TES tank with nine temperature sensors in each layer. In the charging process, the water temperature of each layer was considered the average value. During litchi precooling, the water temperature was represented by the mean value of these 27 temperature sensors.  
Ice thickness, \(\delta_{ice}\), as shown in Figure 2, was the average value of the ice thickness.  
The TES capacity (\(Q_{clv}\)) indicated the sensible heat released by the water cooling and latent heat released by the water freezing. It could be expressed as:  
\[Q_{clv}=m_{mat}c_{mat}(t_{itw}-t_{wat})+m_{ice}(c_{mat}t_{wat}+C_{ice}) \tag{22}\]  
The effective TES capacity (\(Q_{clf}\)) refers to the thermal energy storage that can be used by litchi precooling. It is the part that uses the TES capacity to subtract the part that cannot  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Test**} & \multicolumn{1}{c}{**Charging Time (h)**} & \multicolumn{1}{c}{**Litchi Load (kg)**} & \multicolumn{1}{c}{**Spray Flow Rate**} & \multicolumn{1}{c}{**Water Storage Capacity of TES Tank (kg)**} \\  & & & (L min\({}^{-1}\)) & \\ \hline
1 & 12 & – & – & 1200 \\
2 & 4 & 23 & 30 & 400 \\
3 & 3 & 23 & 30 & 400 \\
4 & 5 & 23 & 30 & 400 \\
5 & 6 & 23 & 30 & 400 \\
6 & 5 & 8 & 30 & 400 \\
7 & 5 & 13 & 30 & 400 \\
8 & 5 & 18 & 30 & 400 \\
9 & 5 & 28 & 30 & 400 \\
10 & 5 & 23 & 20 & 400 \\
11 & 5 & 23 & 40 & 400 \\
12 & 5 & 23 & 50 & 400 \\ \hline \hline \end{tabular}  
* Test 1 was charging test, tests 2–12 were lithci spray hydrocooling tests; test 2 = central comparison point, tests 3–5 = charging time, tests 6–8 = lithci load, and tests 9–11 = spray flow rate.  
\end{table}
Table 4: Conditions of charging and spray hydrocooling tests.  
be used, and that is the part where the water temperature of the TES tank decreases from the initial temperature to the end of precooling temperature. It can be expressed as:  
\[Q_{eff}=Q_{chr-}m_{watt}c_{watt}(t_{itw}-t_{ttw})=m_{watt}c_{watt}(t_{ttw}-t_{watt})+ m_{ice}(c_{watt}t_{watt}+C_{ice}) \tag{23}\]  
\[m_{ice}=\rho_{ice}\pi_{loi}\Bigg{[}\left(\frac{\sum(\delta_{ice}+r_{coi})}{3} \right)^{2}-r_{coi}^{2}\Bigg{]} \tag{24}\]  
The total power consumption (\(E_{tal}\)) including water pump power consumption in the spray precooling test and compressor power consumption in the charging process can be expressed as:  
\[E_{tal}=E_{spr}+E_{cltr} \tag{25}\]  
\(EER\), the energy efficiency ratio, is the ratio of TES capacity to power consumption. In order to obtain the real-time energy efficiency change and average energy efficiency change in the charging process, a 30 min energy efficiency ratio and average energy efficiency ratio are used. The 30 min energy efficiency ratio is the ratio of TES capacity and the energy consumption in 30 min, and the average energy efficiency ratio is the ratio of TES capacity and the energy consumption since the beginning of charging. All are expressed as [37]:  
\[EER=\frac{Q_{chr}}{E_{cltr}} \tag{26}\]  
Precooling capacity (\(m_{spr}\)) refers to the total amount of lithci precooled until finishing precooling in one test.  
Precooling time (\(t_{spr}\)) refers to the time from the beginning of precooling to the end of precooling in one test, when the water reaches 7 \({}^{\circ}\)C.  
Precooling rate (\(u_{spr}\)) is the ratio of precooling capacity to precooling time in one test.  
Average power consumption (\(E_{kg}\)) is the power consumption per kilogram of lithci precooled. It is the most intuitive method to evaluate the cost of lithci precoding and an important index to evaluate the economy of precooling equipment. The average power consumption is given by:  
\[E_{kg}=\frac{E_{tal}}{m_{spr}} \tag{27}\]