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Introduction
Published in Randall F. Barron, Gregory F. Nellis, Cryogenic Heat Transfer, 2017
Randall F. Barron, Gregory F. Nellis
The original (circa 1960) MLI consisted of alternating layers of highly reflecting foil, such as aluminum or copper foil, and a low-conductivity spacer, such as fiberglass paper, Dacron fabric, or silk net. Because the foil material was quite fragile and tended to develop pin holes when crinkled, it has been largely replaced by aluminized Mylar. The reflective layer of aluminum, which is between 30 and 40 nm thick, is vacuum deposited on a sheet of Mylar plastic (polyester film) that is 6–10 μm thick. In some MLI, the reflecting layers are separated by a crinkled or embossed sheet of aluminized Mylar to eliminate the fragile fiberglass paper separator.
On the performance of vacuum insulated panels and sandwiches
Published in Paul Fazio, Hua Ge, Jiwu Rao, Guylaine Desmarais, Research in Building Physics and Building Engineering, 2020
One way to reduce the thermal conductivity within a material is to reduce the conduction within the pores. The most effective way to do this is to evacuate the structure. As a result, vacuum insulated elements show thermal conductivities at about 5 mW/(m · K). At the moment three basic kinds of vacuum insulated elements are available: stainless steel cased VIS elements, foil covered VIP elements and multilayer insulation materials MLI. Even though MLI are not used in the building sector but in cryoengineering and space applications at the moment, they offer some special advantages for further developments.
Thermal and Mechanical Design
Published in Shen-En Qian, Hyperspectral Satellites and System Design, 2020
Most spacecraft flown today are covered with MLI blankets, with cutouts provided for areas where radiators reject internally generated waste heat. MLI blankets are also typically used to protect internal propellant tanks, propellant lines, and cryogenic dewars. Single-layer radiation shields are sometimes used in replace of MLI where less thermal isolation is required, since they are lighter and cheaper to manufacture.
Discharge and electromagnetic radiation behind the hole of simulated charging satellite surface under impact
Published in Waves in Random and Complex Media, 2022
Enling Tang, Liangliang Zhao, Yafei Han, Chuang Chen, Mengzhou Chang
The MLI coating on the satellite surface consists of multi-layer polyimide, aluminum foil and polyester fiber mesh. The three-layer structure of metal mesh/polyester mesh/2A12 aluminum plate is selected as the capacitance formed by equivalent MLI and satellite surface, in which the polyester metal mesh can play an excellent insulating role. The metal mesh is 100 meshes, and the thickness is 0.5 mm. The existence of the hole allows the plasma generated by the impact to enter the metal box through the hole. The structure of the simulated satellite is insulated by high voltage insulating paper and joined by plastic screw. Figure 3 shows the Multi-layer insulation material. Figure 4 shows the structure of the simulated satellite exposed on space environment.
A review on fuel cell electric vehicle powertrain modeling and simulation
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Eda Alpaslan, Sera Ayten Çetinkaya, Ceren Yüksel Alpaydın, S. Aykut Korkmaz, Mustafa Umut Karaoğlan, C. Ozgur Colpan, K. Emrah Erginer, Aytaç Gören
If hydrogen is stored in liquid form, it must be kept below the boiling point of 20 K (−252.87°C, 1 atm) (Durbin and Malardier-Jugroot 2013). Therefore, heat loss from the tank to the environment should be kept as low as possible. For this purpose, cryogenic containers are generally designed with multi layers. The multi-layer insulation (MLI) method, which consists mostly of 45 layers of 1/2-mil aluminized Mylar and 45 layers of Dacron netting, is the most widely used cryogenic container insulation technology (Wesley Louis Johnson 2017). In addition, the sensible heat from boiling can be recovered using a self-evaporating vapor cooling shield (VCS) to improve thermal insulation performance (Chen et al. 2017a). Foam insulation (spray-on foam insulation-SOFI) can be applied to the MLI layer to prevent vacuum degradation in long-term storage (Zheng et al. 2019). The mass balance for a liquid hydrogen tank can be written similarly to a compressed gas tank as shown in Eq. (25). Due to the significant temperature difference (approximately 300 K in many cases) between the inner and outer walls of the cryogenic tank (Winnefeld et al. 2018), the heat transfer mechanisms (conduction in SOFI and conduction and radiation in MLI) should be taken into account in the energy balance (Zheng et al. 2019) (Eqs. (33) to (38)). Considering that there is heat conduction through the SOFI layer, the thermal conductivity of this layer can be expressed as;
Effect of ortho-para conversion on economics of liquid hydrogen tanker with pressure cargo tanks
Published in Ships and Offshore Structures, 2018
Hwalong You, Junkeon Ahn, Sangkwon Jeong, Daejun Chang
There are several representative insulation concepts that can be used to prevent external heat ingress. Multi-layer insulation (MLI) is primarily intended to protect cryogenic inventory from radiation, and it is often used in spacecraft. Vacuum insulation was designed to reduce heat ingress due to radiation, gas conduction and convection. However, it is difficult to apply MLI to complicated shapes, and it is weak to lateral conduction. In addition, vacuum insulation requires a permanently high degree of vacuum, which is easily broken by a small leak. Therefore, poly urethane foam is applied to the surface of the cargo tank. External heat ingress through the insulation and tank can be calculated using the following conditions (Table 3).