## 1 Introduction
(**a**) Curved flow channel; (**b**) temperature difference distribution in a trapezoidal flow channel [5]. [PERSON] et al. [14; 15] conducted experimental tests on accelerated evaporators with nine different structural forms. Their experimental results show that the accelerated evaporator requires less pump power than the reference evaporator in the case of low heat transfer capacity. In this case, the volume and material consumption of the accelerated flow evaporator are less than that of the direct evaporator. However, when the heat transfer capacity is large, the power consumption of the accelerated flow evaporator increases exponentially, which limits its application. This is because the pressure drop of the condensed evaporator is larger at a high Reynolds number. The diverging flow channel structure proposed in this paper can be applied to the field where the reduced flow channel structure cannot be applied. Compared with the number of research papers on the trapezoidal flow channel, relatively fewer studies are available on the curved flow channel. [PERSON] et al. [16] used the CFD method to study the heat transfer and flow performance in a curved pipe with a radius ratio of 0.92. They found that the outer part of the curved pipe has the best convective heat transfer performance by analyzing the Nusselt number at different positions. At the same time, the improvement in heat transfer is mainly due to the eddy current, which also increases the transverse convection of the secondary flow, thus improving the heat transfer characteristics. [PERSON] et al. [17] studied the volumetric entropy generation rate in the sharp-angled corrugated flow channel. The results showed that the total entropy increase gradually increased with the increase in \(Re\). However, when the Reynolds number ranged from 25 to 400, the total entropy increases along the flow channel direction gradually reduced. [PERSON] et al. [18] studied the two-dimensional flow characteristics of corrugated flow channels at different Reynolds numbers (\(100<Re<2123\)). The heat transfer and flow characteristics of the structure in laminar flow and transition flow were studied. The changes of Nusselt number, friction coefficient and area goodness factor at six different amplitudes (0.05 mm, 0.075 mm and 0.1 mm) and wavelengths (0.5 mm and 1 mm) were compared. [PERSON] et al. [19] studied the straight-line flow channel and pin-fin surface with nine different structures using experimental methods. These structures were mainly used in the condenser to enhance the film-wise condensation on the vertical plate. By comparing the sinusoidal-type and pin-type flow channel surfaces, it was found that the sinusoidal-type surface had the best heat transfer performance at the same \(p/l\) ratio (\(p\) is fin pitch and \(l\) is fin height). [PERSON] et al. [20] used numerical simulation methods to study the overall heat transfer performance of sinusoidal-type plate-fin heat exchangers based on fluid-structure interaction analysis. Analysis of the pressure distribution indicated that the maximum pressure value was mainly at the inlet and outlet of the fin, at which the fluctuating pressure value reached a peak value. [PERSON] et al. [21] and [PERSON] et al. [22] carried out CFD analysis of rectangular, hexagonal and sinusoidal flow channels by direct numerical simulation and the evaluated heat transfer and flow performance in different flow channels. However, the curved flow channel studied above is equal in area and shape perpendicular to the flow channel and is different from the flow channel forms defined in this paper. At the same time, in the wet condition in which the phase change occurs, the condensate in the curved flow channel is more likely to flow out of the flow channel, and the condensate at this time is mainly affected by the combined action of the component of gravity on the curved surface and the tensor of the liquid film. Research on the phase change heat transfer will be explored in future research because of the limited length of this paper.