Xinzhi Wang

Commercially Available Activated Carbon Fiber Felt Enables Efficient Solar Steam Generation

Sun-driven steam generation is now possible and has the potential to help meet future energy needs. Current technologies often use solar condensers to increase solar irradiance. More recently, a technology for solar steam generation that uses heated surface water and low optical concentration is reported. In this work, a commercially available activated carbon fiber felt is used to generate steam efficiently under one sun illumination. The evaporation rate and solar conversion efficiency reach 1.22 kg m-2 h-1 and 79.4%, respectively. The local temperature of the evaporator with a floating activated carbon fiber felt reaches 48 °C. Apart from the high absorptivity (about 94%) of the material, the evaporation performance is enhanced thanks to the well-developed pores for improved water supply and steam escape and the low thermal conductivity, which enables reduced bulk water temperature increase. This study helps to find a promising material for solar steam generation using a water evaporator that can be produced economically (∼6

Numerical Investigation on Actively Cooled Thermal Protection Systems with Ni-Based Alloys

/m2) with long-term stability.

Thermal-mechanical response of microscale functional film for infrared window

One of the greatest challenges of hypersonic vehicles is their thermal protection and, more specifically, the cooling of their engine. To simulate the behavior of a complete actively cooled thermal protection system, a computational fluid dynamics and finite element analysis coupling method is applied to calculate the fluid/thermal/stress distributions for steady-state flight conditions. Work has been done on four different Ni-based alloys and three different panel structures. Temperature and stress profiles at the outlet cross section show that the maximum temperature and stress happen on the side that is close to the combustion chamber, and so this is the section on which the active cooling system should focus. It is better to have small rounded chamfers in the panels to decrease the stress concentration at the corners. Failure maps are presented for four Ni-based alloys showing the comparison of their thermostructural performance, which will be helpful for the selection of the materials in an active co...

Direct vapor generation through localized solar heating via carbon-nanotube nanofluid

Abstract Infrared window in hypersonic missile usually suffers complex aerodynamic force/heat during high-speed flight. A finite element method was adopted to simulate the thermal and stress response of microscale functional film for infrared window under different aerodynamic heats/forces conditions. Temperature and stress distribution were obtained with different heat fluxes. There is almost constant stress distribution along the film thickness except a sudden decrease near the substrate. The maximum stresses are located at the points which are 0.5 mm away from the edges. Different film materials result in different stress values. The temperature and stress in ZrN are larger than those in Y 2 O 3 . Besides the numerical simulation, an oxygen propane flame jet impingement test was performed to investigate thermal shock failure of the infrared window. Some place of the window surface has spots damage and some place has line crack damage after thermal shock.