Determination of economical insulation thickness for fordigester based on heat pump heating system

In order to optimize the design of heat pump heating system for biogas engineering and reduce the initial investment and operating cost, economical insulation thickness (EIT) of anaerobic digester was studied in this study. Firstly, the comprehensive heat transfer coefficient theory was applied to simplify the calculation of thermal dissipation load for the digester. The calculation method of the annual dynamic load was obtained by means of hourly meteorological parameters. Then the mathematical model of EIT was developed by annul-cost method. The simplified computational formula of EIT was applied to a project in Shanghai, and the values of EIT were determined between 0.05 and 0.07 m. With 3.5 of performance coefficient of heat pump, the EIT of five insulation materials including expanded polystyrene, extruded polystyrene, phenol resin, polyurethane, polyvinyl chloride were 0.092, 0.063, 0.054, 0.048 and 0.046 m, respectively.