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

138-143This 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%

Measurement of internal pressure and thermal performance in a closed-loop oscillating heat-pipe with check valves (CLOHP/CV)

531-540<span style="mso-bidi-font-family: AdvEPSTIM;mso-fareast-language:JA" lang="EN-GB">The internal pressure and the thermal performance as characteristic parameters in a closed-loop oscillating heat-pipe with check valves (CLOHP/CV) under the normal operating condition have been investigated experimentally. The test CLOHP/CV was made of a copper capillary tube with various inner diameters. The inclination angle and the working temperature have been varied in the experiments. The working fluids of distilled water, ethanol and R123 were used with a filling ratio 50% of the total internal tube volume; the number of meandering turns was 40 and the number of check valves was 2. The lengths of the evaporator, adiabatic and condenser sections are all the same. The evaporator section was heated by electric strip heaters. The heat was removed from the condenser section by forced convective flow of ambient air blowing through the sections. The adiabatic section was well insulated by foam insulation. The thermal performance of the CLOHP/CV was evaluated by calculating the rate of heat transferred from the condenser to ambient air. It was found that the thermal performance of the CLOHP/CV has been improved by increasing the working temperature, the inclination angle and the inner diameter. The best performance of all the test CLOHP/CVs occurred for the case of R123 as working fluid, 2.03 mm inner diameter, 90° inclination angle and the working temperature of 200°C, where the maximum internal pressure was 7.53 MPa and the minimum thermal resistance was 0.048°C/W. </span