Perbandingan Penambahan Surfaktan Polyethylene Glycol Terhadap Konduktivitas Termal Fluida Terdispersi Partikel Mikro Berbasis Karbon dari Arang Tempurung Sawit dan Tempurung Kelapa. = Comparison of Addition Polyethylene Glycol Surfactant to Thermal Conductivity of Carbon-Based Microparticle Dispersed Fluids from Palm Kernel Shell and Coconut Shell Ash.