Experimental investigation of effects of extremely low pumping speed on isothermal performance and filling ratio of sint
- PDF / 3,904,054 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 91 Downloads / 150 Views
Experimental investigation of effects of extremely low pumping speed on isothermal performance and filling ratio of sintered copper heat pipe Jing Zhang1 · Li‑xian Lian1 · Ying Liu1 · Ya‑cong Liu2 Received: 28 September 2019 / Accepted: 1 January 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In the present research, extremely low pumping speed and special charging method are employed to investigate the effects of pumping speed on the filling ratio and isothermal performance of heat pipe. Results show that the saturation degree of porous wick is about 92% and water loss during vacuuming is significantly decreased when pumping speed is decreased to 0.1 m3 h−1. In addition, excessive extension of evacuation time cannot decrease NCG level further but increase water loss. NCG level after first vacuuming is high, and the temperature difference (ΔT) along heat pipe cooling section is larger than 7 °C. But, ΔT can be significantly decreased when secondary degassing is conducted. Increasing heating temperature and duration both obviously decrease NCG level and increase isothermal performance. The maximum ΔT of the heat pipe can be decreased to 0.5 °C when secondary degassing was conducted at 140 °C for 100 s. Moreover, the decrease in shrunken section length decreases the isothermal performance and 40 mm is enough in the present study. Finally, the water loss of whole fabrication process can be decreased to ~ 0.015 g leading to approximately 1 mass% water loss in heat pipe. Keywords Isothermal performance · Noncondensable gas · Heat pipe · Filling–vacuuming · Water loss List of symbols A Cross-sectional area (cm2) h Natural convection heat transfer coefficient of air (W m−2 K−1) L Total wick length (cm) m Mass (g) Q Heat load flowing through the heat pipe (W) R Thermal resistance (°C W−1) S Area of copper surface directly contacted with air (cm2) t Time (s) T Temperature (°C) V Total volume of voids in porous wick (cm3)
* Ying Liu [email protected] 1
Key Laboratory of Advanced Special Materials and Novel Manufacturing Technologies of Ministry of Education, College of Materials Science and Engineering, Sichuan University, Chengdu 610065, People’s Republic of China
Chengde Petroleum College, Chengde 067000, People’s Republic of China
2
Greek symbols α Saturation degree/filling ratio of the porous wick ε The porosity of the porous wick Δ Difference 𝜖 Emissivity of copper surface ρ Density (g cm−3) σ Stefan–Boltzmann constant (5.670373 × 10−8 W m−2 K−4) Subscripts 1st First vacuuming 2nd Secondary degassing a Adiabatic c Cooler c1–c5 Condensate e1–e5 Evaporative h Heater loss Loss l Liquid s Saturation t Total w Wick ∞ Ambient
13
Vol.:(0123456789)
Introduction As a heat transfer device basing on liquid–vapor phase change, heat pipe has been widely used in solar energy collection [1, 2], lithium-ion battery thermal management [3–6], electronic cooling [7, 8] and phase change material thermal storage systems [9, 10], owing to its high thermal conductivity, superior d
Data Loading...
