Tensile properties of finger-jointed lumber under high-temperature and oxygen-free conditions

A model for engineered wood was developed that considers the parallel-to-grain tensile strength of finger-jointed lumber at high temperatures relevant to fire conditions. The finger-jointed lumber was composed of Douglas fir, larch, and poplar wood with phenol-resorcinol-formaldehyde (PRF) as an adhesive. The tensile properties of the finger-jointed lumber were evaluated at high temperatures under oxygen-free conditions, i.e. in a nitrogen atmosphere. A combination of chemical and thermal-physical property analysis of the PRF adhesive and microscopic observations on the glueline was used to discuss the reduction of tensile strength of the parallel-to-grain finger-jointed lumber at variable temperature. The results show that the tensile strength of the finger-jointed lumber decreased linearly with increasing temperature. The parallel-to-grain tensile strength of the PRF finger-jointed samples at 20 and 280 °C were 84 and 5% of the tensile strength of the solid wood at 20 °C, respectively. The thermal-physical properties and scanning electron microscopy analysis revealed that the pyrolysis intensity of the PRF adhesive was lower than that of the wood at 220 °C or higher.

Fluidization in Supercritical Water: Heat Transfer between Particle and Supercritical Water

Supercritical water fluidized bed reactor, which is used to gasify biomass and produce hydrogen, is a new member of fluidized bed family. Forced convection heat transfer between supercritical water and particles is a major basic heat transfer mechanism in supercritical water fluidized bed reactor. The object of this paper was to determine the heat transfer characteristics for a forced convection between a spherical particle and supercritical water (SCW) in a range of pressure from 23 to 27 MPa and temperature from 637 to 697 K. A numerical model fully accounting for thermal physical property variation of SCW has been solved using a finite volume method with Reynolds number up to 200. Comparing with constant property flow, high velocity and temperature gradient in the vicinity of the particle surface were observed when the variable thermal physical property of SCW was incorporated in calculation. Based on the numerical results, a correlation that takes into account the large thermal physical property variation was proposed for predicting Nusselt number.

Physical Property and Thermal Physical Property of Microencapsulated Phase Change Material Slurry

Microencapsulated phase change material (PCM) slurry is a kind of novel heat transfer fluid called latent functionally thermal fluid. Unlike conventional (sensible) materials, when the PCM reach the temperature at which they begin phase change (its melting point), they absorb large amounts of heat with little or no temperature change. Due to this, the heat transfer ability and energy transport ability can be obviously improved. Therefore, they have many potentially important applications in some fields such as energy storage, thermal conditioning of buildings, waste heat recovery, off peak power utilization, heat pump systems, space applications. In present study, the core materials are encapsulated with membrane of synthetic material. And the core materials are composed of several kinds of n-paraffin waxes (mainly nonadecane) and the membrane is a type of melamine resin. The range of diameter of the PCM particles is distributed from 0 μm to 4.5 μm, and its average diameter is 0.74 μm. The thickness of melamine resin is about 11nm. The melting point of the PCM is about 304K. Physical properties, such as density, diameter and its distribution of microencapsulated PCM slurry are investigated. Meanwhile, the thermal physical property, apparent specific heat, is determined by a Differential Scanning Calorimeter (DSC). Also, the influence of mass concentration has been discussed.