متن زیرا به فارسی روان ترجمه کن و فقط از کاراکتر و اعدادهای فارسی استفاده کن و از کاراکتر و اعداد های زبان دیگر به خصوص چینی استفاده نکن
    
    2. Description of the experiment 
2.1. Nanofluid preparation 
In the present study, an aqueous suspension of MWCNTs (8 wt%) 
purchased from Organic Chemistry Ltd. of the Chinese Academy of 
Sciences (Chengdu, China) was used as the source nanofluid because of 
its high suspension stability. The outer and inner diameters of MWCNTs 
are 30–80 nm and 5–15 nm, respectively, and its length is less than 10 
um. To prepare the ethanol aqueous solutions of MWCNTs, each CNT 
nanofluid sample was further diluted by adding an appropriate amount 
of pure water and ethanol. It is worth noting that the volume ratio of 
water and ethanol in the mixture to form base fluid was remained at 1:1 
to achieve desirable heat transfer performance of the OHP [35]. Addi tionally, TNWDIS was also harnessed as a supplementary surfactant to 
stabilize the suspension. 
Then, each prepared nanofluid sample was subject to magnetic force 
agitation for 20 min and then ultrasonic vibrated for about 20 min to 
further improve the stability and dispersion uniformity. After above 
procedures, the water–ethanol mixture-based CNT nanofluids were ob tained at different mass concentrations ranging from 0.05 to 0.5 wt and they could be stably suspended as displayed in Fig. 1(a). After a 
month stay, the high dispersion stability against aggregation was further 
confirmed because no obvious precipitation was observed at the bottom 
of these tubes, which can be verified by these inverted tubes (see Fig. 1 
(b)). Fig. 2 depicts the transmission electronic microscope (TEM) image 
of the size and morphology of dispersed CNT fibers. It can be found that 
the CNT fibers are partially entangled but distributed relatively 
uniformly. 
2.2. Experimental setup 
The experimental setup is composed of a hybrid oscillating heat pipe 
assembly, an electrical heating unit, an air cooling unit, and a data 
measurement and acquisition system as illustrated in Fig. 3(a). The 
three-turn OHP was fabricated by the combination of a copper flat-plate 
evaporator involving six parallel circular channels inside and a capillary 
copper tube condenser. Fig. 3(b) lists the overall size and geometric 
parameters of the hybrid OHP. It is noted that step-holes were fabricated 
at the two endings of each circular channel in the flat-plate evaporator to 
match the inner/outer diameters of capillary tubes, which ensures the 
close welding connection between the evaporator plate and capillary 
tubes. 
To simulate the EV battery cooling on the basis of OHP, the evapo rator section of the hybrid OHP was sandwiched between two flat-plate 
electric heaters of the same size as the evaporator plate (see Fig. 3(c)). 
The electric heater approximately acted as a commercial rectangular 
LiFePO4 power battery (having the size of 126 mm in length and 66 mm 
in width) to simulate the battery pack and could generate required 
power inputs by adjusting the voltage supply. Similar methods with 
respect to the heat generation simulation of battery pack were also re ported by some other groups [31,33,49]. As for the transient thermal 
problem of EV battery during the charging/discharging processes, it can 
also be approximately simulated by the electric heater if the thermal 
condition is well understood and revealed. To reduce the contact ther mal resistance between the OHP evaporator and electric heaters, ther mal paste (OMEGATHERM 201) with thermal conductivity of 2.3 W/ 
(m⋅
◦C) was used. Additionally, the outside of the evaporator was 
wrapped with insulation cotton (2 cm in thickness and 0.03 W/(m⋅
◦C) in 
thermal conductivity) and aluminum foil to minimize the heat loss to the 
external environment. 
To monitor the temperature variations on the OHP as well as on the 
simulated EV battery, eighteen T-type thermocouples with a same 
diameter of 0.1 mm (±0.2 ◦C in accuracy) were used. Twelve thermo couples were mounted to measure temperatures at different OHP re gions. Among them, six thermocouples (T1-T6) and four thermocouples(T13-T16) were placed at the copper plate evaporator and the tube condenser section, respectively (see Fig. 3(a)). In addition, six thermo couples (T7-T12) were adhered to one of the electric heaters to measure 
the surface temperatures of simulated battery pack (heater plate). All 
temperature measurements were recorded by the data logger (Agilent 
34970A) and transferred to a computer. 
The electric heating unit provides the power input to the OHP, 
mainly consisting of an AC voltage stabilizer (JONCHN SVC-II), a 
voltage regulator (DELIXI TDGC2-3kVA), a power meter (GWINSTEK 
GPM-8212) and the above mentioned electric heaters. The condenser 
region was cooled by air forced convection driven by two coaxial fans at 
an ambient temperature of 25 ± 1 ◦C. A large number of copper radial 
fins (0.2 mm thickness and 5 mm height) were used on the outside of 
condenser-tubes with the aid of the press-fit technology to reduce the 
contact thermal resistance. 
In this study, the OHP was placed at the vertical orientation and 
worked at the bottom heating mode, and the filling ratio was remained 
at 35%. During the experiment, the power input to the evaporator was 
stepwise increased at each power input, and temperature signals were 
recorded after the system reached a quasi-steady state. Then, the 
average temperatures were obtained to assess the OHP performance as well as the thermal control effect of simulated EV battery packs. After 
each nanofluid OHP experiment, the internal surface of OHP would be 
well washed to greatly diminish the CNT nanofiber deposition effect on 
the following OHP performance.