Conductivity deviations of constant bulk- and layer-averaged frost

Air-source heat pump performance is often hindered by frost formation on the evaporator plates. Frost conductivity models aimed at mitigating the performance losses of the frost layer utilize bulk- and layer-averaged properties, ignoring differences in frost morphology. Two scripts were developed to generate frost structures and calculate their properties respectively. Air conduction above and below side branches, interbranch interactions, and loop interactions were found to affect the total conductivity up to 3 % by analyzing aggregations of basic structures. For randomly generated samples, differences in verticality accounted for the largest conductivity differences of 5.6 %.