Thermal performance characteristics of a pulsating heat pipe at various nonuniform heating conditions

•Thermal performance of a PHP is measured at various nonuniform heating conditions and filling ratios.•Thermal resistance is analyzed as a function of dimensionless heat difference, heat input, and filling ratio.•Optimal filling ratios are determined with respect to nonuniformity of heat input in the evaporator section.•Contour maps for effective thermal conductivity are proposed to provide design guides of PHPs.