A Calculation Method of Average Fluid Temperature in Solar Collector

doi:10.12096/j.2096-4528.pgt.21071

Abstract

Abstract:

The solar collector is an important equipment for photo-thermal conversion. It can be used not only for centralized energy utilization by tower thermal power generation technology, but also for distributed energy utilization by disc thermal power generation technology. Therefore, it is necessary to evaluate the thermal performance of solar collectors. A new method was proposed to calculate the average fluid temperature of solar collectors. The experimental results show that the calculation results are in good agreement with the experimental data, which proves that the method can predict the average fluid temperature of solar collector. The effect of different parameters on thermal efficiency was also investigated to better acquire the thermal performance of solar collectors. The results show that when the input power is constant, increasing the flow rate can effectively improve the efficiency of solar collector. When the flow rate is constant, the efficiency of solar collector increases first and then decreases with the increase of input power. The efficiency of solar collector is inversely proportional to the inlet temperature and proportional to the ambient temperature.

Key words: solar thermal power generation, solar collector, average fluid temperature, thermal performance

CLC Number:

TK 51

Li XU, Feihu SUN, Zhi LI, Qiangqiang ZHANG. A Calculation Method of Average Fluid Temperature in Solar Collector[J]. Power Generation Technology, 2022, 43(3): 405-412.

Figures/Tables 15

Fig. 1 Structure of solar collector

Fig. 2 Structure of receiver panel

Fig. 3 Structure of experimental platform

Tab. 1 Structural parameters of solar collector

结构	管板数	单个管板吸热管数	外径/mm	壁厚/mm	采光口面积/m²
腔式太阳能集热器	7	4	14	1.4	0.12

Tab. 2 Parameter values under reference condition

m ˙

/(kg·s^-1)

v_w/(m·s^-1)

ε_p

ε_r

k_p/

(W·m^-1·K^-1)

Tab. 2 Parameter values under reference condition

参数

Q_net,in/kW

T_a/K

T_fi/K

m ˙

/(kg·s^-1)

v_w/(m·s^-1)

ε_p

ε_r

k_p/

(W·m^-1·K^-1)

数值

140

293.15

493.15

0.5

0.66

0.8

Tab. 3 Ranges and uncertainties of test parameters

参数	范围	不确定度
输入功率	0~200 kW	±0.5%
入口温度	0~510 ℃	±1.5 ℃
出口温度	0~510 ℃	±1.5 ℃
环境温度	5~40 ℃	±1.5 ℃
体积流量	0~24 L/min	±1%

Fig. 4 Inlet temperature and input power of solar collector

Fig. 5 Ambient temperature and mass flow rate of solar collector

Fig. 6 Comparison between calculation results and experimental data of average fluid temperature

Fig. 7 Maximum relative error between calculation results and experimental data of average fluid temperature under different working conditions

Fig. 8 Distribution of input power of solar collector

Fig. 9 Thermal efficiency of solar collector under different input power distributions

Fig. 10 Effect of inlet and ambient temperature on thermal efficiency of solar collector

Fig. 11 Effect of input power and mass flow rate on thermal efficiency of solar collector

Fig. 12 Sensitivity analysis of different parameters on thermal efficiency

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