# Documentation

 Symbol Name Unit A $a_0$ Coefficient a for partial transient temperature rise 1/s $a_{12}$ Distance between phase 1 and 2 mm $a_{23}$ Distance between phase 2 and 3 mm $a_{31}$ Distance between phase 3 and 1 mm $A_{ab}$ Cross-sectional area of armour bedding mm$^2$ $A_{ar}$ Cross-sectional area of armour mm$^2$ $A_c$ Cross-sectional area of conductor mm$^2$ $a_c$ Skin and proximity effect coefficient a for PAC/GIL conductor $A_{comp}$ Cross-sectional area of compartment m$^2$ $A_d$ Cross-sectional area of duct wall mm$^2$ $A_{d,fill}$ Free cross-sectional area inside duct mm$^2$ $A_{di}$ Surface of duct inner wall m$^2$ $A_{do}$ Surface of duct outer wall m$^2$ $A_e$ Surface of object m$^2$ $A_{encl}$ Cross-sectional area of enclosure mm$^2$ $a_{encl}$ Skin and proximity effect coefficient a for PAC/GIL enclosure $A_{er}$ Surface of object m$^2$ $A_f$ Cross-sectional area of filler mm$^2$ $A_{fluid}$ Cross-sectional area of fluid mm$^2$ $A_i$ Cross-sectional area of insulation mm$^2$ $A_{it}$ Cross-sectional area of insulation (IEC 60853) mm² $A_j$ Cross-sectional area of jacket mm$^2$ $A_k$ Thermal property constant A mm/s$^{1/2}$ $a_m$ Mean distance between the phases mm $A_{pipe}$ Cross-sectional area of fluid-filled pipe mm$^2$ $A_{prot}$ Cross-sectional area of protective cover mm$^2$ $a_{S1}$ Length of 1st section (minor) p.u. $a_{S2}$ Length of 2nd section (medium) p.u. $a_{S3}$ Length of 3rd section (major) p.u. $A_{sc}$ Cross-sectional area of screen mm$^2$ $A_{scb}$ Cross-sectional area of screen beddig mm$^2$ $A_{scs}$ Cross-sectional area of screen serving mm$^2$ $A_{sh}$ Cross-sectional area of sheath mm$^2$ $A_{shj}$ Cross-sectional area of sheath jacket mm$^2$ $a_{shj}$ Factor $a_{shj}$ for jacket around each core $A_{skid}$ Cross-sectional area of skid wires mm$^2$ $A_{sp}$ Cross-sectional area of steel pipe mm$^2$ $A_t$ Cross-sectional area of the tunnel m$^2$ $A_{tape}$ Cross-sectional area of bedding/serving tapes mm$^2$ $a_{type}$ Construction of armour $\alpha_0$ Constant depending on the burial depth $\alpha_{ar}$ Temperature coefficient of armour material 1/K $\alpha_{at}$ Heat transfer coefficient to channel wall W/(K.m$^2$) $\alpha_c$ Temperature coefficient of conductor material 1/K $\alpha_{encl}$ Temperature coefficient of enclosure material 1/K $\alpha_f$ Phase shift ° $\alpha_{gas}$ Thermal diffusivity for gas m$^2$/s $\alpha_M$ Factor $\alpha_M$ $\alpha_{sa}$ Heat transfer coefficient for convection W/(K.m$^2$) $\alpha_{sc}$ Temperature coefficient of screen material 1/K $\alpha_{sh}$ Temperature coefficient of sheath material 1/K $\alpha_{skid}$ Temperature coefficient of skid wire material 1/K $\alpha_{sp}$ Temperature coefficient of steel pipe material 1/K $\alpha_{st}$ Heat transfer coefficient for radiation W/(K.m$^2$) $\alpha_{sys}$ Inclination angle in degrees ° $\alpha_t$ Conductor to surface attainment factor