Methods for Evaluation of Radiation View Factor: A Review

Abstract

Evaluation of radiation view factor is animportant task for calculating exact radiation heat load.The shape factor is a function of the spatial orientation between surfaces. Shape factor is mainly depending on thegeometry of body, incident and leaving radiation on the body. View factor is a purely geometric parameter and is independent of the surface properties and temperature.In the present work, different analytical methods for calculating the view factor are discussed with their parametric comparison in detail.In any cryogenics system, two wall vessels configuration is generally adopted. The inner vessel always kept at the cryogenic temperature as per the cryogenic fluid and outer vessel is generally at the atmospheric temperature. These vessels are separated with the vacuum insulation. Hence radiation heat load impinges on the inner cryogenic vessel. The general configuration of both the vessels is cylindrical in nature. The length of outer cylindrical vessel can be equal to or more than the length of inner cylindrical vessel.A special case of cryopump has been considered as a case study in which the inner vessel cylindrical length is less than the outer vessel length. The calculation of shape factor between two concentric finite cylinders with different length becomes important to calculate the exact radiation heat load. In the present work matrix method, Howell’s method and cross string methods were implemented for this problem and comparison of the different shape factor value is obtained.