Thermal Control Technology of Primary Mirror of 2.5 m Class Solar Telescope

Ran Zhu; Bozhong Gu; Jieqian Xu; Zhiyong Zhang; Xiangyan Yuan

doi:10.3788/AOS201838.1112001

Acta Optica Sinica, Volume. 38, Issue 11, 1112001(2018)

Thermal Control Technology of Primary Mirror of 2.5 m Class Solar Telescope

Ran Zhu^1,2,3、*, Bozhong Gu^1,2、*, Jieqian Xu^1,2,3, Zhiyong Zhang^1,2, and Xiangyan Yuan^1,2

¹ Nanjing Institute of Astronomical Optics & Technology, National Astronomical Observatories, Chinese Academy of Sciences, Nanjing, Jiangsu 210042, China;

² Key Laboratory of Astronomical Optics & Technology, Chinese Academy of Sciences, Nanjing, Jiangsu 210042, China;

³ University of Chinese Academy of Sciences, Beijing 100049, China

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Figures & Tables(20)

Fig. 1. Primary mirror profile

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Fig. 2. Solid domain of initial model

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Fig. 3. Fluid domain of initial model

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Fig. 4. Complete initial 3D model

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Fig. 5. (a) Temperature filed of primary mirror reflection plane; (b) temperature filed of airout 1 and airout 2

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Fig. 6. (a) Light weighted primary mirror and (b) its profile

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Fig. 7. 3D model of solid domain

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Fig. 8. 3D model of fluid domain

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Fig. 9. Complete 3D model

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Fig. 10. (a) Average temperature of primary mirror reflection plane as a function of inlet velocity; (b) mirror seeing as a function of inlet velocity

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Fig. 11. Temperature filed of primary mirror reflection plane

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Fig. 12. Structure of air knife

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Fig. 13. Complete 3D model with air knife

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Fig. 14. Mirror seeing as a function of velocity of air knife. (a) Temperature of cooling air of 283.15 K; (b) temperature of cooling air of 284.15 K; (c) temperature of cooling air of 285.15 K; (d) temperature of cooling air is 286.15 K

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Fig. 15. Temperature filed of primary mirror reflection plane at forced convection

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Table 1. Physical properties of materials

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Table 1. Physical properties of materials

Material	Thermal conductivity /(W·K^-1·m^-1)	Specific heat /(J·kg^-1·K^-1)	Density /(kg·m^-3)	Thermal expansion coefficient /K^-1
Zerodur	1.64	1006.43	2530	-
Steel	16.27	1006.43	8030	-
PTFE	0.1	1006.43	2200	-
Al	202.4	871	2719	-
Air	0.0242	1006.43	1.225	0.0033

Table 2. Variation of related parameters with inlet velocity

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Table 2. Variation of related parameters with inlet velocity

Inlet velocity /(m·s^-1)	$\begin{matrix} {T_{\max}}_{} \end{matrix}$ /K	ΔT /K	$\begin{matrix} {T_{ave}}_{} \end{matrix}$ /K	Heat 1 /W	Heat 2 /W	Heat 3 /W	Heat 4 /W	Error /%
0.5	293.985	2.679	293.28	3.2749	18.9544	22.2293	22.2222	0.0321
1.0	291.473	1.761	290.986	1.7663	20.4628	22.2291	22.2222	0.0310
1.5	290.554	1.371	290.156	1.2483	20.9816	22.2299	22.2222	0.0345
2.0	289.817	1.242	289.434	0.9119	21.3177	22.2296	22.2222	0.0334
2.5	289.344	1.191	288.965	0.4712	21.7583	22.2295	22.2222	0.0328
3.0	289.058	1.129	288.578	0.1718	22.0578	22.2296	22.2222	0.0332
3.5	288.744	1.117	288.248	0.0414	22.1882	22.2296	22.2222	0.0333
4.0	288.452	1.048	287.965	-0.0537	22.2843	22.2305	22.2222	0.0374
4.5	288.289	1.104	287.741	-0.1892	22.4186	22.2295	22.2222	0.0327
5.0	287.979	0.883	287.524	-0.2940	22.5224	22.2284	22.2222	0.0277

Table 3. Comparison of related parameters of primary mirror reflection plane at different working conditions

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Table 3. Comparison of related parameters of primary mirror reflection plane at different working conditions

Condition	Temperature of inlet /K	Inlet velocity /(m·s^-1)	Velocity of air knife /(m·s^-1)	Highest temperature /K	Temperature difference /K	Mirror seeing /arcsec
Air knife off	283.15	3.5	-	288.744	1.117	0.0183
Air knife on	283.15	3	3	288.672	0.686	0.017

Table 4. Variation trend of related parameters at different velocities of air knife

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Table 4. Variation trend of related parameters at different velocities of air knife

Velocity of air knife /(m·s^-1)	$\begin{matrix} {T_{\max}}_{} \end{matrix}$ /K	ΔT /K	$\begin{matrix} {T_{ave}}_{} \end{matrix}$ /K	Heat 1 /W	Heat 2 /W	Heat 3 /W	Heat 4 /W	Error /%
1	288.804	0.815	288.459	0.4261	21.8039	22.2301	22.2222	0.0353
2	288.723	0.730	288.428	0.4646	21.7655	22.2301	22.2222	0.0357
3	288.672	0.686	288.404	0.6098	21.6208	22.2306	22.2222	0.0377
4	288.647	0.680	288.389	0.6798	21.5510	22.2309	22.2222	0.0390
5	288.636	0.675	288.376	0.7355	21.4954	22.2310	22.2222	0.0396
6	288.635	0.668	288.358	0.8099	21.4208	22.2307	22.2222	0.0382
7	288.634	0.660	288.344	0.8622	21.3682	22.2303	22.2222	0.0367
8	288.629	0.648	288.339	0.8788	21.3515	22.2303	22.2222	0.0362
9	288.623	0.637	288.335	0.8898	21.3404	22.2302	22.2222	0.0359
10	288.621	0.633	288.327	0.8938	21.3364	22.2302	22.2222	0.0358

Table 5. Comparison of domestic and foreign research
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Table 5. Comparison of domestic and foreign research
Telescope Δ $\begin{matrix} {T_{1}}_{} \end{matrix}$ /K Mirror seeing /arcsec
GREGOR ≤2 -
DKIST ≤1 ≤0.05
EST ≤2 -
CLST ≤1 ≤0.05
ISMAT <0.6 <0.02

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Ran Zhu, Bozhong Gu, Jieqian Xu, Zhiyong Zhang, Xiangyan Yuan. Thermal Control Technology of Primary Mirror of 2.5 m Class Solar Telescope[J]. Acta Optica Sinica, 2018, 38(11): 1112001

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