Flow Channelization Method to Enhance Transformer Radiator Cooling Capacity

Abstract

Most oil-cooled equipment like transformers are provided with radiators or heat exchangers, for the heated oil to exchange heat with the surrounding air by natural convection cooling, assisting the overall cooling process. While such radiators are effective accessories in controlling equipment temperature rise, it is ever desirable to further enhance the cooling capacity by design modifications or incorporating simplistic and cost-effective cooling technologies. In this study, computational fluid dynamic (CFD) analysis has been performed to evaluate the possibility of improving radiator performance by flow channelizing structures. Significant benefits (up to 17% increase in heat transfer coefficient) of imposing such structures, like a top chimney and an enclosure surrounding the radiator, were obtained. Although several past studies have confirmed that natural convection cooling effect can be intensified by flow channelization, the phenomenon is unique to a particular application. Given the wide variety in applications, in terms of shape, size, and structural features, it is necessary to study the effect in a given application of interest. This study points to a new direction in enhancing the cooling capacity of transformer radiators, inducing flow channelization, an easy-to-implement and cost-effective technology. Further, the study offers interesting learnings regarding flow channelization effects, which are invaluable guidelines for designers of future radiators.

Thermal evaluation optimization analysis for non‐rated load oil‐natural air‐natural transformer with auxiliary cooling equipment

“…Considering the differences in windage area of different radiators, the radiators are divided into three categories: (1) no cooling fans are arranged, that is, radiators ③ and ⑤ in B-Phase, (2) a cooling fan is arranged for two groups of radiators, that is, radiators ① and ② in A-Phase, ⑥ and ⑦ in C-Phase, (3) a cooling fan is arranged for one group of radiator, that is, radiator ④ in B-Phase. Based on the analysis in 2.2.1, h airN of radiators ③ and ⑤ working in natural convection can be calculated by Equation (11), and the calculated result is 4.66 W/(m 2 ⋅K) for the case of K = 1.0. For the radiators in category (2), A-phase radiators ① and ② are taken as examples to calculate h airF .…”

“…Combining with the temperature rise test data of the target transformer shown in Table 2, the value of h airN for the case of rated load (K = 1.0) and ambient temperature with 298 K can be obtained by (11) and the calculation result is 4.66 W/(m 2 ⋅K). In addition, formula (11) still can be applied to calculate the…”

“…Therefore, it is necessary to improve the heat dissipation capacity of the panel-type radiator for the ONAN transformer [10]. In [11,12], some methods were proposed to improve the average heat transfer coefficient on the air side of the radiator by adjusting the structural design of the radiator. Subsequently, some material performance optimization measures, such as doping graphene [13] and adding nanoparticles [14], were applied to improve the thermal conductivity of radiators.…”

“…FIGURE 4Mixed convection diagram of panel type radiator coefficient on the air side (i.e. h airN ) is shown in(11) …”

A Method for Fans’ Potential Malfunction Detection of ONAF Transformer Using Top-Oil Temperature Monitoring

“…In addition, S. C. Zhao et al has discussed the effect of heat conduction of radiator wall on the overall heat dissipation [7]. For the structure optimization of radiator with fans, S. Dasgupta et al [8] has proved that adding chimneys or enclosures around the radiator can enhance the air flow performance. To improve the efficiency of calculation, a complete thermo-hydraulic radiator model was proposed which combined the fan characteristics and the radiator geometry [9].…”