Study on dynamic and static performance of external tubular molten salt receiver

doi:10.11949/0438-1157.20191351

Abstract

Abstract:

A 50 MW external tubular molten salt receiver model is developed for simulating the dynamic and static performance of the receiver in ideal conditions and actual meteorological conditions. The response curve is given to show that the maximum surface temperature, temperature gradient, and heat dissipation power of the receiver are basically proportional to the changes in direct normal irradiance (abbreviated as DNI); the efficiency grows with increase in direct normal irradiance, and the slope, however, decreases; wind speed mainly affects convection heat dissipation power; in the presence of direct normal irradiance step disturbance, the response time of the molten salt outlet temperature, the maximum surface temperature and the heat dissipation power of the receiver is longer than that of the receiver tube axial temperature gradient, and gradually the efficiency returns approximately to the level before a sudden change; flow step down have a greater impact on the receiver performance. Using the quantitative relationship between the characteristic parameters of the heat sink and the direct solar irradiance and molten salt flux can improve the molten salt flux adjustment strategy in operation.

Key words: solar energy, radiation, heat transfer, external tubular molten salt receiver, dynamic and static performance

摘要：

以某50 MW塔式光热发电项目外露管式熔盐吸热器为研究对象，进行了建模，通过理想条件下的动静态仿真和实际气象条件下的模拟，给出吸热器特性参数的动静态响应曲线，提出了吸热器出口盐温控制的改进方法，分析了其在实际气象条件下的运行特点，总结了以下规律：吸热器表面最高温度、温度梯度、散热功率与太阳法向直射辐照度的变化基本呈正比关系；效率随太阳法向直射辐照度增大而升高但斜率逐渐减小；风速主要影响对流散热功率；太阳法向直射辐照度扰动下吸热器出口熔盐温度、表面最高温度、散热功率的过渡过程响应时间较吸热管轴向温度梯度更长，效率在瞬间突变后会重新逐渐回复到接近扰动前的水平；流量阶跃下降对吸热器性能影响更大。利用吸热器特性参数与太阳法向直射辐照度和熔盐流量三者间的定量关系可改进运行中的熔盐流量调整策略。

关键词: 太阳能, 辐射, 传热, 外露管式熔盐吸热器, 动静态特性

CLC Number:

TK 513

Mei XU, Huaiwu PENG, Dongsheng NIU, Xiao WANG, Bin XIAO, Zhi ZHOU, Yanglong DUAN, Junfeng ZHANG. Study on dynamic and static performance of external tubular molten salt receiver[J]. CIESC Journal, 2020, 71(5): 2049-2060.

徐玫, 彭怀午, 牛东圣, 王晓, 肖斌, 周治, 段杨龙, 张俊峰. 外露管式熔盐吸热器动静态特性研究[J]. 化工学报, 2020, 71(5): 2049-2060.

Figures/Tables 23

Fig.1 Schematic of typical molten salt receiver process flow

Fig.2 Typical panel structure of external tubular molten salt receiver

Fig.3 Micro-element model of a single receiver tube

Fig.4 Tube wall heat transfer model

Table 1 Structure characteristics of Solar Two receiver

参数	数值
额定功率/MW	42.2
吸热管长度/m	6.2
管屏数目	24
各管屏吸热管数目	32
吸热器直径/m	5.1
吸热管外径/m	0.025
吸热管壁厚/m	0.00125

Table 2 Comparisons between simulation results and test results

工况	工况参数					模型计算结果验证
工况	环境温度/℃	风速/（m/s）	平均能流密度/（kW/m²）	熔盐流量/（kg/s）	入口熔盐温度/℃	实测出口熔盐温度/℃	计算出口熔盐温度/℃	偏差/%	实测效率	计算效率	偏差/%
1	32	0.6	341	80	294	555	556	0.18	0.888	0.895	0.80
2	33	1.2	372	90	300	552	555	0.54	0.884	0.899	1.64
3	33	1	373	90	304	556	560	0.69	0.88	0.898	2.05
4	14	2	289	67	302	564	562	-0.34	0.881	0.878	-0.34
5	18	3.2	340	78	303	564	567	0.55	0.874	0.882	0.92
6	18	0.9	302	69	301	564	567	0.45	0.87	0.884	1.63
7	17	2.5	311	70	298	564	567	0.55	0.871	0.827	1.04

Fig.5 Flux density distribution on receiver in rated condition

Fig.6 Surface temperature distribution of receiver in rated condition

Fig.8 Heat dissipation power density distribution of receiver in rated condition

Fig.7 Temperature gradient distribution of receiver tube in rated condition

Fig.9 Parameter variations of receiver performance with direct normal irradiance

Fig.10 Heat dissipation power variations with wind speed

Fig.11 Parameter variations of receiver performance with flow rate

Fig.12 Parameter variations of receiver performance in presence of direct normal irradiance step disturbance

Fig.13 Variations of molten salt out temperature in receiver flow path 1 in presence of direct normal irradiance 20% step increase

Fig.14 Variations of receiver surface temperature in presence of direct normal irradiance 20% step increase

Fig.15 Parameter variations of receiver performance in presence of flow rate step disturbance

Fig.16 Variations of molten salt out temperature in receiver flow path 1 in presence of flow rate 20% step down

Fig.17 Variations of receiver surface temperature in presence of flow rate 20% step down

Table 3 Polynomial coefficient of relationship between change percentage of direct normal irradiance and receiver performance parameters

系数

出口熔盐温度变化

百分比/%

吸热器表面最高温度

变化百分比/%

吸热器散热功率变化

百分比/%

Table 4 Polynomial coefficient of relationship between change percentage of salt flow rate and receiver performance parameters

系数

出口熔盐温度变化

百分比/%

吸热器表面最高温度

变化百分比/%

吸热器散热功率变化

百分比/%

Fig.18 Comparison between traditional and improved practice of receiver salt outlet temperature control

Fig.19 Variations of meteorological parameters and receiver performance parameters in a cloudy day

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