1. A cryogenic heat exchanger with bypass and throttling and its thermodynamic analysis Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, China X Tao, D L Liu, L Y Wang, J Shen, Z H Gan* 01-July-2015 Cryogenic Engineering Conference & International Cryogenic Materials Conference Tucson, Arizona, June 28 – July 2, 2015 Presentation ID: C3OrK Paper ID: 208 E-mail ： gan_zhihua@zju.edu.cn Tel ： 0571-87951930

2. 2 1. Heat exchangers in precooled J-T cycle 2. A heat exchanger with bypass and throttling 3. Entropy analysis of heat transfer and flow 4. Summary Outline

3. 3 Introduction to the cycle 1~100mW @1~10 K SPICA @JAXA SMILES @JAXA Planck @ESA Astro-H @JAXA JWST @NASA

4. HX.3 is the key component 4

5. ε=97.17% ， T h,out =7.06K ， ΔT c,end =2.83K 4 He property deteriorates T-L ε= 100% ， T h,out =6.78K ， ΔT c,end =2.55K 5

6. 6 1. Heat exchangers in precooled J-T cycle 2. A heat exchanger with bypass and throttling 3. Entropy analysis of heat transfer and flow 4. Summary Outline

7. 7 New structure of HX.3

8. 8 Questions 1.Where to locate? − β 2.How much mass flow to extract? − α

9. Q R variation β 1 =24% ， β 2 =7.5 % ， α=47.5% （ Q R max -Q R 0 ） / Q R 0 =8.14% β 2 indicates the position of bypass and throttling α indicates the amount of bypass mass 9

10. changed structure ， T h,out =6.36K ， ΔT c,end =2.13K original structure ， T h,out =7.06K ， ΔT c,end =2.83K β1β1 ΔT decreases β2β2 β3β3 10

11. Effects of changed structure P r =6 Q R0 =0.28mW Q Rmax =10.50mW 11

12. Effects of changed structure 12

13. 13 1. Heat exchangers in precooled J-T cycle 2. A heat exchanger with bypass and throttling 3. Entropy analysis of heat transfer and flow 4. Summary Outline

14. Entropy generation within HX.3 ΔT decreases in the changed structure. So entropy generation due to heat transfer decreases 14

15. Two structures original structure changed structure 15

16. Entropy comparison 16

17. 17 1. Heat exchangers in precooled J-T cycle 2. A heat exchanger with bypass and throttling 3. Entropy analysis of heat transfer and flow 4. Summary Outline

18. Summary 18 A cryogenic heat exchanger with bypass and throttling is introduced in this paper. The effect of the changed structure is remarkable at low pressure ratio. When the pressure ratio of the J-T cycle is 6, the original structure approximatlely achieves no refrigeration capacity, while the changed structure achieves the refrigeration capacity of 10.5 mW. In the changed structure, the entropy generations of heat transfer and flow decrease by a half, the entropy generations of the bypass and throttling is introduced, and the entropy increase of heat absorption increases.

19. Cryogenic Engineering Conference & International Cryogenic Materials Conference Tucson, Arizona, June 28 – July 2, 2015 Presentation ID: C3OrK Paper ID: 208 Contact: GAN Zhihua Pro. GAN Zhihua Zhejiang University gan_zhihua@zju.edu.cn The work is financially supported by NSFC and SRFDP from China.