Thermal Engineering

Heat pipes are heat transfer devices that enhances large amount of heat which works on the principle of evaporation and condensation of a working fluid. Inspite of wide application of heat pipe in microelectronics cooling system the trend of the chips performance and power utilization has been increased each year and a complete understanding of mechanism has not yet been completed even though it has the ability to operate against gravity and a greater maximum heat transport capability. This paper gives you a detailed literature review about the various parameters that affect the operational characteristics of circular heat pipe. Moreover the thermal resistance and heat transfer capability are affected by the choice of working fluid, the tilt angle, the fill ratio, thermal properties, angle of inclination and heat input.

This work deals with the elaboration and the physical characterization of thermally modified wood with boiling palm oil. The heat treatment consists of dipping successively the wood into two baths of oil, the first one at a temperature about 200°C for 30 minutes and the second at ambient temperature of 23°C. This resulted in important color changes of treated specimens. The wood species used for the study are Sapelli and Ayous, two Cameroonian hardwoods. A compared study of the physical properties of treated and untreated wood was made. Hygroscopicity of heat?treated wood has been tested. Samples were dipped in water and then kept in a room with a relative humidity of 65% and a temperature of 23 °C. The samples were periodically weighed over a period of 8 days. The conclusion was that during a short period the water permeability of heat?treated Sapelli was 70 per cent lower than that of normal dried Sapelli. The same result was found for Ayous. Heat treatment significantly reduces the tangential and radial swelling. The Specific gravity of heat treated wood was almost constant, but higher than that untreated wood. After an adequate treatment, the moisture content of these woods after dipping in water for a long time was less than 7%. It is therefore possible for these treated woods to be used outside without biological attack due to moisture. In addition, the dimensions of treated wood were almost constant.

The Plate Heat Exchanger(PHE) consists of a series of parallel plates that are corrugated both to increase turbulence and to give mechanical rigidity . They normally have flow ports in all four corners and are clamped together in a frame that carries bushes and nuzzles lined up with the plate ports and connected to the external pipework that carries the two liquid streams .The plates themselves are fitted with gaskets, which are shaped and located both to prevent external leakage and to direct the two liquids normally counter currently through the relatively narrow passage between alternate pairs of heat transfer plates. One of the important feature of corrugated plate heat exchangers is their wavy surfaces. This feature has many advantages and of courses some disadvantages. For example, it enhances total heat transfer coefficient, but increases pressure drops and naturally running costs. The effects of wavelength on thermal performance of the heat exchanger was investigated in this study. This paper also presents a study on calculating wavelength, which can be useful in optimization process in order to find optimum value of the wavelength.

In this Paper numerical study with swept ramp injection in supersonic combustion of hydrogen has been presented. Coupled implicit scheme with finite rate chemistry model and K-? Turbulence model have been used for modeling of supersonic combustion. The main issue in supersonic combustion is proper mixing within short burst of time. Because of the step on the top wall of the combustor, there exists an expansion fan generated just on the top wall at the entrance of the combustor, which is interacts with the oblique shock wave formed upstream of the combustor due to the shear layer deflecting into the core flow. The static pressures along the walls are normalized by the static pressure of the core flow. The present result is very promising and demonstrates that flamelet approach seems to be feasible to high-speed flows. The stagnation temperature in the combustion reaches up to 2830 k. Fluctuation in pressure and Mach number was due to shock train.