Research on heat transfer characteristics and tube layout optimization of indirect electric heating furnace

doi:10.12034/j.issn.1009-606X.225326

Abstract

Abstract:

The shell-and-tube electric heating furnace that uses high-temperature molten salt as an indirect heat carrier to heat thermal oil is a new type of indirect heating furnace that can achieve green zero-carbon emissions from traditional thermal oil furnaces. Based on natural convection and Boussinesq assumption, five different pipe layout methods of molten salt indirect electric heating furnaces are studied by CFD simulation. After comprehensive comparison, the basic configuration of hexagonal tube layout is determined, and the influence of different tube spacing on the heat transfer process inside high-temperature molten salt electric heating furnaces is further analyzed. The results show that, with a square pipe arrangement, at a spacing of 30 mm, the flow resistance of molten salt is high, resulting in low heat transfer efficiency, and the outlet temperature is 315.3℃. When the tube spacing is increased to 40 mm, the flow resistance decreases and heat transfer reaches its maximum, yielding the maximum outlet temperature of 315.7℃. This configuration is suitable for designs with small area and low requirement on temperature uniformity. In the case of a rectangular pipe arrangement, as the pipe spacing increases, the flow space of molten salt expands, the heat flow disturbance is reduced, and the natural convection loop becomes more complete. The highest outlet temperature is achieved with a tube spacing of 50 mm. However, as the spacing continues to increase, the heat flow concentration decreases, and the heat transfer efficiency is reduced. A pipe spacing of 50 mm in the rectangular arrangement is suitable for designs requiring larger flow spaces and higher heat transfer efficiency.

Key words: indirect heating, electric heating furnace, structural optimization, parameter optimization, heat transfer characteristics

摘要：

高温熔盐作为间接载热体加热导热油的管壳式电加热炉是一种新型间接加热炉，可以实现传统导热油炉的绿色零碳排放。本工作基于自然对流和Boussinesq假设，通过CFD模拟研究了熔盐间接电加热炉的5种布管方式，经过综合对比确定了六边形布管的基本构型，进一步分析了不同布管间距对高温熔盐电加热炉内传热过程的影响规律。结果表明，局部电加热管正方形布管情况下，间距30 mm下，熔盐流动阻力大，传热效率低，出口温度315.3℃；管间距升至40 mm时，阻力降低且换热最强，出口温度最高315.7℃，适合小面积、均匀性要求较低的设计。局部电加热管长方形布管情况下，随着管间距增加，熔盐的流动空间变大，热流干扰减弱，自然对流循环更完整，管间距50 mm时出口温度最高；管间距继续增大时，热流聚集程度下降，热量传递效率降低；50 mm的管间距长方形排布方案适合需要较大流动空间和热量传递效率的设计。

关键词: 间接加热, 电加热炉, 结构优化, 参数优化, 传热特性

CLC Number:

TE65

Juan WANG, Rui ZHANG, Chunhua JIA, Guanda WANG. Research on heat transfer characteristics and tube layout optimization of indirect electric heating furnace[J]. The Chinese Journal of Process Engineering, 2026, 26(9): 976-986.

王娟, 张瑞, 贾春桦, 王冠达. 间接电加热炉传热特性及布管优化研究[J]. 过程工程学报, 2026, 26(9): 976-986.

Figures/Tables 15

Fig.1 Schematic diagram of molten salt indirect electric heating furnace

Fig.2 Layout diagrams of electric heating tube

Table 1 Fitting equations for molten salt thermal physical properties

Thermal physical property	Equation	Temperature range/℃
Density/(kg/m³)	-0.748T+2092	200~550
Specific heat capacity/[J/(kg·K)]	-0.634T+1655	200~550
Thermal conductivity/[W/(m·K)]	-2.5×10^-4T+0.469	200~550
Viscosity/[kg/(m·s)]	-2.0×10^-12T³+2.1×10^-9T²-7.1×10^-4T+0.0836	200~550

Fig.3 Average temperature of Y-Z sections in the furnace under different number of grids

Fig.4 Comparison of experimental and simulated temperature of thermal oil at inlet and outlet

Fig.5 Schematic diagram of cross-sections

Fig.6 Velocity flow diagrams for Y-Z sections of different layouts of heating tubes

Fig.7 Temperature distribution of Y-Z sections of different layouts of heating tubes

Fig.8 Layout schematic diagram of electric heating tube

Fig.9 Velocity flow diagrams of Y-Z sections with different tube spacings b and c in square arrangement

Fig.10 Section temperature distributions of different tube spacings b and c in square arrangement

Fig.11 Outlet temperature of thermal oil with different tube spacings b and c in square arrangement

Fig.12 Velocity flow diagrams of Y-Z sections with different tube spacings a in rectangular arrangement

Fig.13 Section temperature distributions of different tube spacings a in rectangular arrangement

Fig.14 Outlet temperature of thermal oil with different tube spacings a in rectangular arrangement

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