Heat Transfer Through a Multilayer Insulation System as a Function of Pressure in the Cryostat Vacuum Space

1998 ◽  
pp. 1313-1318 ◽  
Author(s):  
M. A. Green
Keyword(s):  
Heat Transfer ◽  
Insulation System ◽  
Multilayer Insulation ◽  
Vacuum Space

HEAT TRANSFER INVESTIGATION FOR A MULTILAYER INSULATION SYSTEM VIA RADIATIVE-CONDUCTIVE APPROACH UNDER LOW TEMPERATURE CONDITIONS IN SPACE

2020 ◽  
Vol 19 (2) ◽  
pp. 70
Author(s):  
G. N. Lacerda ◽  
M. F. Curi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Field ◽  
Insulation System ◽  
Final Temperature ◽  
Space Applications ◽  
Conduction Heat Transfer ◽  
Stationary Temperature Field ◽  
Layer Density ◽  
Multilayer Insulation

Thermal insulation is an important area, not restricted to mechanical engineering, but widely studied in environmentalissues, such as global warming and, above all, energy-saving, since controlling the heat flux on microprocessorsthrough temperature control on components in space applications. This work focuses on controlling the temperature incomponents that could not lose or gain so much heat in space, especiallywhen the overall safety of sending satellites onspecific missions is required. To ensure that, Multilayer Insulation (MLI) is used. With fluid mechanics and radiation-conductionheat transfer theory, it was possible to calculate the transient and stationary temperature field and heat flux inMLI. The boundary temperatures are specified at 300K and 4K. The results, from solving the resulting discretized ODE,simulated with fsolve and odeintScipy subroutines in Python, able to solve the equations numerically, were shown. Thedata given by the simulation was able to indicate the impacts of varying the layer density, emissivity of screen, the distancebetween screens and the perforation coefficient in stationary and transient approaches. A way to simulate the performanceof MLI numerically was presented. Modifying emissivity (e) showed variations higher than in the perforation coefficient(ξ). Layer density controls the distance between layers (d ), changing the conduction heat transfer. In the transient casesimulation, it was possible to notice that varying parameters impact in time to reach steady-state and final temperature.

Radiation Effects in Heat Transfer Mechanisms by Dispersive Materials: Numerical Analysis in Diffusive Enclosure Model of Thermal Insulation

2018 ◽  
Vol 26 (04) ◽  
pp. 1850036 ◽  
Author(s):  
Muhd Azi Bin Che Seliman ◽  
Yoshio Hirasawa
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Thermal Insulation ◽  
Radiation Effects ◽  
View Factor ◽  
Insulation Material ◽  
Insulation System ◽  
Multilayer Insulation ◽  
Insulation Performance ◽  
Transfer Mechanisms

The current development of global warming and CO2 emission problems cannot be overlooked. Thus, global scale measures of efforts are becoming crucial. Thermal properties of insulation materials need to be considered as high performance thermal insulation systems are crucial for efficient energy saving. The most important parameter as indicator of a thermal insulation material is the effective thermal conductivity, but elements that affect the thermal insulation performance are rather complicated. Generally, conduction and radiation heat transfer are needed to be separately considered in precisely evaluating the thermal insulation performance as they coexist in the heat transfer process inside a multilayer insulation system. In this paper, numerical analysis of a complete diffusive enclosure model as a thermal insulation is observed to investigate the radiation effects by its dispersive heat transfer mechanisms. View factor of each relatively large dispersed material is derived in the enclosure model, where it is applicable to various shapes and any particular arrangements of dispersed materials. As this paper is the first part of a three-part working research paper, numerical analysis in this paper is carried out by assuming that the medium within the space inside the insulation system is taken to be nonparticipating, therefore conduction and convection effects during the heat exchange are negligible. This paper will be continued with application of the numerical analysis in observing radiation heating effects by wall-ceiling integration towards indoor environment and radiation–conduction heat transfer mechanisms in one-dimensional multilayer insulation system.

scholarly journals Heat transfer coefficient α of insulation liquid used in power transformers, based on measurements

2018 ◽  
Vol 19 ◽  
pp. 01016
Author(s):  
Przemyslaw Goscinski ◽  
Zbigniew Nadolny
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Transfer Factor ◽  
Heat Load ◽  
Surface Heat ◽  
Power Transformers ◽  
Negative Consequences ◽  
Insulation System ◽  
Heat Transfer Factor ◽  
Factor Α

Proper work of the power transformer is determined by many factors. One of them is relatively low operating temperature of the transformer. Too high temperature has many negative consequences, such as fast aging process of the insulation system. The temperature depends on the load of transmission line, losses and heat exchange in transformer. Heat exchange depends on heat transfer factor α of insulation liquid, which is a component of insulation system of transformer. This factor depends on many factors: the type of insulation liquid, the length of the heating element (windings), temperature, winding surface heat load, the winding position (vertical, horizontal), place on the winding (upper, middle or bottom part). The article presents the results of the measurement of heat transfer factor α as a function of type of insulation liquid, winding surface heat load, and place on the windings. The results will be used by designers and operators of power transformers.

Multilayer Insulation Venting During Payload Depressurization

2005 ◽  
Author(s):  
Ingrid Cotoros ◽  
Ab Hashemi
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Thermal Control ◽  
Pressure Differential ◽  
State Condition ◽  
Space Application ◽  
Steady State Condition ◽  
Satellite Systems ◽  
Multilayer Insulation

Multilayer Insulation (MLI) blankets consist of closely spaced aluminum coated shields that are spaced apart to reduce heat transfer between the payload and the environment, particularly in vacuum. In space application, satellite systems and sub-systems are wrapped in MLI blankets to thermally isolate them from the environment and achieve thermal control requirements. During spacecraft launch, the payload undergoes a rapid depressurization before reaching steady state condition. The MLI blankets are usually perforated and/or connected at the boundaries with Velcro strips to allow out-gassing. The blankets can lose their integrity and functionality if the depressurization process is too rapid: the out-gassing flow can tear the perforations, and the pressure differential built-up across the blanket can pull the Velcro strips apart. This paper describes the design and modeling of depressurization through X-slits cut into the blanket and Velcro strips taped along the sides. A methodology is developed, and a model for quantifying the pressure differential build-up is described and applied to a payload enclosure aboard a Delta II rocket.

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