Prediction of overall heat transfer coefficient for RMI insulation using the test and analysis

Both parts of shell and layers have different thermal transfer flow; shell-part is conductivity loss, layer is convective and radiative loss that would contribute to calculate the total heat value with difficulty. We developed the new method about prediction of RMI's total value by separating the shell and layer as a function of heat resistivity. Whereas heat transfer value at the insulation shell is calculated by CFD analysis according to various insulation sizes, multi-layer would be done by thermal test. These predicted models are compared with final insulation sample of overall heat transfer value for the validation. RMI insulation was investigated by GHP (guarded hot plate) measuring instrument (inner-layer) and thermal analysis simulation(CFD method) to predict the approximate value of overall heat transfer. The results are as follows. - Thickness of out-shell as same meaning of outshell ratio is determined very carefully at RMI design. Because it can lead to very large changes in heat transfer. For example, whereas thickness of out-shell with 0.1mm(0.13%) shows 0.16 W/m²K through surface of out-shell, that of 0.4mm(0.53%) thickness is 0.49 W/m²K which is increased nonlinearly. - Inner-layer and out-shell of RMI is arranged in parallel, so that overall heat transfer coefficient would be written with sum of each part. For example, at the condition of 70 .deg. C, inner-layer part(0.06mm) is 0.56 W/m²K and out-shell part(0.7mm) is 0.72 W/m²K, and overall value is 1.28 W/m²K. - We could expect that heat transfer value is changed according to out-shell ratio, because out-shell ratio as conductivity loss is connected with insulation size and inner-layer as radiation blocking is independent