# The Study of Novel Self-Rewetting Fluid Application to Loop Heat Pipe
## 2 Materials and Methods
### LHP Heat Performance Test  
The parameters of the LHP test system are shown in Table 1. In the design of LHP, the basic requirements, such as heating area, space requirement, cooling target wattage, etc., as well as safety should be considered. Additionally, the materials of each component of the system, such as the working fluid, evaporator and other component materials, piping materials, wick materials, etc., should be selected to meet the requirements [10; 19]. We should consider the space volume as a factor, then design the external dimensions of the components. In the heat transfer experiment, the Ni wick was used for the heat transfer test, and then aqueous solutions of water, butanol 6% and 2-butanol 20% were used as the working fluid.  
Figure 4: (a) Wick parameter measurement platform. (b) Porosity measurement.  
Figure 5 is the schematic diagram of the heat transfer performance test experiment. During the performance test, the thermocouple (T-Type) was arranged to measure the temperature of each part of the LHP, and the measurement points of each part were arranged as shown in the figure. The total thermal resistance value (R\({}_{\text{LHP}}\)) is obtained by bringing the condenser inlet (T\({}_{\text{c,in}}\)), evaporator wall temperature (T\({}_{\text{evap}}\)), and power supply wattage (Q) into Equation (6). Meanwhile, Ref. [10] pointed out that SRF has better heat transfer performance at higher operating temperatures with the need for high power density heat dissipation components, such as solar energy storage in the energy field according to [PERSON] et al. [20]. Therefore, this experimental performance test continues to increase the heat load (Q) until LHP system performance failure, that is, the LHP system test stops.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Working Fluid** & **Self-Rewetting Fluids** \\ \hline Heat load (W) & 25–500 \\ Ambient temperature (\({}^{\circ}\)C) & 20 \\ Evaporator & \\ Total length (mm) & 65 \\ Outer/inner diameter (mm) & 15.5/12.5 \\ Active length (mm) & 40 \\ Compensation chamber volume (cm\({}^{3}\)) & 57 \\ Vapor line & \\ Outer/inner diameter (mm) & 6/4 \\ Length (mm) & 470 \\ Liquid Line & \\ Outer/inner diameter (mm) & 6/4 \\ Length (mm) & 583 \\ Condenser & \\ Outer/inner diameter (mm) & 6/4 \\ Length (mm) & 800 \\ Cooling water flow rate (L/min) & 4 \\ Heat sink temperature (\({}^{\circ}\)C) & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 1: LHP system parameters.  
Figure 5: LHP heat transfer performance testing system setup.  
In this paper, the performance of LHP is measured by the relative relationship between temperature-wattage (T \(-\) Q) and thermal-resistance-wattage (R \(-\) Q) to determine the performance.  
\[\mathrm{R_{LHP}}=\frac{\mathrm{T_{evap}-T_{c}}}{\mathrm{Q}} \tag{6}\]  
Water, butanol 6% and 2-butanol 20% are tested as the working fluid. The ambient temperature is 25 \({}^{\circ}\)C, and the circulating water temperature of the condenser is 10 \({}^{\circ}\)C. The error of the thermocouple is \(\pm\)0.2 \({}^{\circ}\)C. The error analysis is based on the relative inaccuracy analysis proposed by [PERSON] [21], and the error of the total thermal resistance of the system is \(\pm\)1.9-16.2%.