Measurements and simulations of transient characteristics of heat pipes
The rejection of heat generated by components and circuits is a very important aspect in design of electronics systems. Heat pipes are very effective, low cost elements, which can be used in cooling systems. This paper presents the modelling and measurements of the heat and mass transfer in heat pipes. The physical model includes the effects of liquid evaporation and condensation inside the heat pipe. The internal vapour flow was fully simulated using computational fluid dynamics. The theory has been compared with experimental measurements using thermographic camera and contact thermometers. The main purpose of this study is to determine the effective heat pipe thermal conductivity in transient state during start up the pipe operation and temperature increase.
Numerical investigation of characteristics of wick structure and working fluid of U-shape heat pipe for CPU cooling
Abstract In the current study, the effects of the wick structures and working fluids characteristics on U-shape heat pipe performance were numerically presented. A two-dimensional FEM simulation was performed on U-shape heat pipe to analyze the temperature and the pressure distributions inside the heat pipe. In order to reduce the pressure arising in the area of the wick to increase heat transport capability at the liquid-wick region, a comparative numerical study was made by using methanol and water as working fluids with sintered powder and screen mesh wicks. The simulation was performed by using ANSYS/FLOTRAN software with heat input of 10 W at forced convection. The results showed that the use of sintered copper powder wick resulted in a small temperature difference between the evaporator and condenser compared to screen mesh wick. The use of screen mesh wick caused a decrease in the pressure drop in liquid-wick region while the use of methanol as working fluid increased the liquid pressure drop.
Wood Microbiology: Decay and Its Prevention
Introductory text on the principles of decay and discoloration processes in wood, with emphasis on the major fungal damages which may develop during the growth, storage, and use of wood. The characteristics, detection, effects, and control of microbial attacks are stressed. Provides a synthesis of the current literature on wood microbiology, a rapidly expanding field of study. (Abstractor's note: This is an important resource for conservation researchers studying the decay of wood in art and architecture.) The following is a list of chapter headings: 1) Introduction to wood microbiology; 2) Wood deterioration agents; 3) Characteristics and classification of fungi and bacteria; 4) Factors affecting the growth and survival of fungi in wood (fungal ecology); 5) Fungal metabolism in relation to wood decay; 6) The decay setting: some structural, chemical, and moisture features of wood in relation to decay development; 7) General features, recognition, and anatomical aspects of wood decay; 8) Chemical changes in wood caused by decay fungi; 9) Ultrastructural features of wood decay; 10) Changes caused by decay fungi in the strength and physical properties of wood; 11) Colonization and microbial interactions in wood decay; 12) Decays originating in the stems of living trees; 13) Biodeterioration of stored wood and its control; 14) Wood stains and discolorations; 15) Decay problems associated with some major uses of wood products; 16) Detection of internal decay; 17) Paint mildew and related degradative problems; 18) Natural decay resistance (wood durability); 19) Chemical protection of wood (wood preservation); and 20) Some trends in wood microbiology research and a new emphasis (biotechnology). -- AATA