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Vegetable oils have been seen as promising surrogates to petroleum diesel in compression ignition internal combustion engines, showing similar performance and combustion characteristics of the fossil fuel. Nevertheless, the use of straight (crude) vegetable oil (SVO) is unfavorable due to its high viscosity, which affects the Sauter Mean Diameter of fuel spray and, consequently, fuel-air mixing process, resulting in incomplete combustion. The SVO heating, as well as transesterification and blending with diesel or additives, are some of the techniques to reduce its viscosity and enable its use. Of these the most simple and direct is the heating and was used in this paper to evaluate the performance and emissions of a diesel engine fueled with preheated soybean oil (PSO) by electrical resistances. The experiments were carried out in a single cylinder four-stroke compression ignition engine with mechanical fuel injection.

The microstructure characterization of tubular wicks is discussed using an image analysis method, mercury intrusion porosimetry and Arquimedes method. The central objective of this work is to determine the wide convenience of the image analysis technique for wick characterization. It is demonstrate that the image analysis technique is an appropriate tool to determine correlation function, total porosity and pore size distribution in two-dimensional (2-D) binary images of microstructures. The correlation function is used to simulate the 3-D reconstruction of porous structure. The images were obtained from a set of wick samples made of sintered nickel, through scanning electronic microscopy (SEM). A computer program (Imago) was developed and used in the work. The mercury intrusion porosimetry is also used to provide information about the breakthrough diameter of porous material. Results show porosity of about 60% and effective pore size less than 4 μm.

A small scale CPL (Capillary Pumped Loop) is proposed to be tested under microgravity condition. The CPL consists basically of one solar absorber plate, one radiator plate and one reservoir to control the loop operation system. The heat load required for testing the CPL is supplied by the solar absorber plate. One capillary pump made of sintered nickel is planned to be attached to the absorber plate. Preliminary results regarding the expected performance for the CPL are presented, taking into account the maximum and the minimum solar radiation along an equatorial and elliptic orbit. A solar power up to 33 W is expected to be transferred from the absorber plate to the radiator plate, using ammonia as the working fluid.

Circumferentially grooved heat pipes have been studied as capillary pumps to be used in two-phase heat transfer loops. Experimental results up to 1.7 W/cm2 were found for Freon 11 as the working fluid. To improve the knowledge of the performance of these capillary pumps, some design parameters are now studied. The heat transport capability and the capillary pumping pressure are analyzed for different values of the groove width, groove opening angle and inner radius of the capillary pump. Theoretical results indicates somewhat better performance for capillary pumps with rectangular grooves than with trapezoidal grooves. Fine groove widths and small values of inner radius are also desirable.

Circumferentially grooved heat pipe evaporators have been proposed as an alternative solution to obtain high capillary pressure and large liquid cross sections to reduce the viscous pressure losses in the liquid flow. Such evaporators have been employed in a capillary pumped two-phase loop and first results have been reported for loop operation in the mechanical pump assisted mode. Additional tests have been carried out in order to determine the performance of the loop also in the capillary pumped mode. Using freon 11 as the working fluid, heat fluxes up to 12 kW/m2 have been measured. For ammonia, the corresponding value is estimated to be about 78 kW/m2. A theoretical analysis is also presented in order to understand differing performances of the individual capillary pumps.