Heat transfer for laminar thermally developing flow in parallel-plates using the asymptotic method
Heat transfer for laminar, thermally developing flow in parallel-plates is investigated using the asymptotic method. There are two asymptotes for local, and mean Nusselt numbers (Nuz and Num) in the parallel-plates thermal entrance problem at both uniform wall temperature (UWT) and uniform heat flux (UHF). The first asymptote corresponds to very small value of dimensionless axial coordinate (z∗). The second asymptote corresponds to very high value of dimensionless axial coordinate (z∗). Using the methods discussed by Churchill and Usagi (1972, “General Expression for the Correlation of Rates of Transfer and Other Phenomena,” AIChE J., 18(6), pp. 1121–1128), the fitting parameter in the proposed model can be determined. Comparisons of the asymptotic model with the analytical and numerical solutions available in the literature are presented.
Modeling horizontal storage tanks with encapsulated phase change materials for building performance simulation
The current article describes a model developed to simulate the performance of a horizontal storage tank filled with commercially available, slab-like, macro-encapsulated phase change material. The model is implemented as a component for the TRNSYS simulation program, and is intended for integration into whole building energy analysis. It is based on one-dimensional conduction and uses the thermo-physical properties of the phase change material to maps its thermal behavior, considering hysteresis in the enthalpy-temperature curve. The validity of the modeling assumptions is assessed using a detailed finite-element model and basic dimensional analysis. Experimentally measured thermal behavior of a full-scale phase change material storage unit is used to validate the model. A variety of flow rates, inlet temperature profiles and temperature intervals are evaluated in 13 distinct tests. Comparisons between measurements and simulations indicate the validated model can simulate the behavior of such phase change material storage tanks and be used to improve their design for specific applications.
Formation and Strength of Magnesia Whiskers
The formation of single-crystal magnesia whiskers during the compressive deformation of single crystals at room temperatures is described. These whiskers can have strengths of the order of millions of pounds per square inch. They are formed during fracture as a result of the discontinuous propagation of cracks which are mechanically relieving internal stresses resulting from plastic flow