Design and construction of an oven for drying palm bunch using glycerine as fuel together with using closed-loop oscillating heat-pipe with check valves (CLOHP/CV) heat exchanger for waste heat recovery

Abstract

This research addresses design and construction of an oven (2 m x 3 m x 2 m) for effectively drying palm bunch using glycerin as a fuel and a closed-loop oscillating heat-pipe with check valves (CLOHP/CV) as a heat exchanger for waste heat recovery. In each experiment, palm bunches (500 kg) were baked in oven with and without CLOHP/CV heat exchanger. CLOHP/CV (0.2 m x 0.8 m x 0.5 m) is made of copper tubes (inner diam, 2.03 mm). Working fluids were distilled water, ethanol and R134a. Waste heat from oven was recovered by heat exchanger and was beneficial for pre-heating the air in combustion process. Pre-heating was useful in burning glycerine, and distribution of heat inside oven with CLOHP/CV was better than without CLOHP/CV. Consequently, palm bunches received uniform heat that restrained enzyme thus slowing dissolution reactions that would otherwise produce free fatty acids and cause loss of palm oil. Use of a CLOHP/CV also reduced moisture content of palm bunches to 1.2 wt% on dry basis. When using oven with CLOHP/CV as a heat exchanger with R134a as working fluid, the highest thermal efficiency of drying palm bunch was 42.4%, highest effectiveness of CLOHP/CV was 43.0% and highest efficiency of glycerin stove was 45.0%.