Convective heat transfer from circular cylinders located within perforated cylindrical shrouds

The influence of perforated cylindrical shrouds on the convective heat transfer to circular cylinders in transverse flow has been studied experimentally. Geometries studied were similar to those used in industrial platinum resistance thermometers. The influence of Reynolds number, ventilation factor (ratio of the open area to the total surface area of shroud), radius ratio (ratio of shroud's inside radius to bare cylinder's radius), and shroud orientation with respect to flow were studied. The experiments showed that perforated shrouds with ventilation factors in the range 0.1 to 0.4 and radius ratios in the range 1.1 to 2.1 could enhance the convective heat transfer to bare cylinders up to 50%. The maximum enhancement occurred for a radius ratio of 1.4 and ventilation factors between 0.2 and 0.3. It was found that shroud orientation influenced the heat transfer, with maximum heat transfer generally occurring when the shroud's holes were centered on either side of the stagnation line. However, the hole orientation effect is of second order compared to the influence of ventilation factor and radius ratio

Heat Transfer Measurement and Modeling in Rigid High-Temperature Reusable Surface Insulation Tiles

Heat transfer in rigid reusable surface insulations was investigated. Steady-state thermal conductivity measurements in a vacuum were used to determine the combined contribution of radiation and solid conduction components of heat transfer. Thermal conductivity measurements at higher pressures were then used to estimate the effective insulation characteristic length for gas conduction modeling. The thermal conductivity of the insulation can then be estimated at any temperature and pressure in any gaseous media. The methodology was validated by comparing estimated thermal conductivities with published data on a rigid high-temperature silica reusable surface insulation tile. The methodology was also applied to the alumina enhanced thermal barrier tiles. Thermal contact resistance for thermal conductivity measurements on rigid tiles was also investigated. A technique was developed to effectively eliminate thermal contact resistance on the rigid tile s cold-side surface for the thermal conductivity measurements

Measurement of Heat Transfer in Unbonded Silica Fibrous Insulation and Comparison with Theory

Effective thermal conductivity of a high porosity unbonded silica fibrous insulation specimen was measured over a pressure range of 0.001 to 750 torr (0.1 to 101.3 x 10(exp 3) Pa), and with large temperature gradients maintained across the sample thickness: hot side temperature range of 360 to 1360 K, with the cold side at room temperature. The measurements were compared with the theoretical solution of combined radiation/conduction heat transfer. The previously developed radiation heat transfer model used in this study is based on a modified diffusion approximation, and uses deterministic parameters that define the composition and morphology of the medium: distributions of fiber size and orientation, fiber volume fractions, and the spectral complex refractive index of the fibers. The close agreement between experimental and theoretical data further verifies the theoretical model over a wide range of temperatures and pressures

Heat Transfer in High Temperature Multilayer Insulation

High temperature multilayer insulations have been investigated as an effective component of thermal-protection systems for atmospheric re-entry of reusable launch vehicles. Heat transfer in multilayer insulations consisting of thin, gold-coated, ceramic reflective foils and Saffil(TradeMark) fibrous insulation spacers was studied both numerically and experimentally. A finite volume numerical thermal model using combined conduction (gaseous and solid) and radiation in porous media was developed. A two-flux model with anisotropic scattering was used for radiation heat transfer in the fibrous insulation spacers between the reflective foils. The thermal model was validated by comparison with effective thermal conductivity measurements in an apparatus based on ASTM standard C201. Measurements were performed at environmental pressures in the range from 1x10(exp -4) to 760 torr over the temperature range from 300 to 1300 K. Four multilayer samples with nominal densities of 48 kg/cu m were tested. The first sample was 13.3 mm thick and had four evenly spaced reflective foils. The other three samples were 26.6 mm thick and utilized either one, two, or four reflective foils, located near the hot boundary with nominal foil spacing of 1.7 mm. The validated thermal model was then used to study relevant design parameters, such as reflective foil spacing and location in the stack-up and coating of one or both sides of foils

Combined Heat Transfer in High-Porosity High-Temperature Fibrous Insulations: Theory and Experimental Validation

Combined radiation and conduction heat transfer through various high-temperature, high-porosity, unbonded (loose) fibrous insulations was modeled based on first principles. The diffusion approximation was used for modeling the radiation component of heat transfer in the optically thick insulations. The relevant parameters needed for the heat transfer model were derived from experimental data. Semi-empirical formulations were used to model the solid conduction contribution of heat transfer in fibrous insulations with the relevant parameters inferred from thermal conductivity measurements at cryogenic temperatures in a vacuum. The specific extinction coefficient for radiation heat transfer was obtained from high-temperature steady-state thermal measurements with large temperature gradients maintained across the sample thickness in a vacuum. Standard gas conduction modeling was used in the heat transfer formulation. This heat transfer modeling methodology was applied to silica, two types of alumina, and a zirconia-based fibrous insulation, and to a variation of opacified fibrous insulation (OFI). OFI is a class of insulations manufactured by embedding efficient ceramic opacifiers in various unbonded fibrous insulations to significantly attenuate the radiation component of heat transfer. The heat transfer modeling methodology was validated by comparison with more rigorous analytical solutions and with standard thermal conductivity measurements. The validated heat transfer model is applicable to various densities of these high-porosity insulations as long as the fiber properties are the same (index of refraction, size distribution, orientation, and length). Furthermore, the heat transfer data for these insulations can be obtained at any static pressure in any working gas environment without the need to perform tests in various gases at various pressures

COMPARISON OF SECOND-DEGREE BURNS HEALING TIME IN TWO METHODS OF DRESSING WITH FUNDERMOL HERBAL OINTMENT AND% 1 SILVER SULFADIAZINE OINTMENT‏

BACKGROUND: Burn wounds are one of the health problems in modern societies that are associated with irreparable harms and many side problems for patients and their families. Infection due to burn wounds is the main cause of death in such patients. One of the methods to prevent infection of burn wounds is topical antibiotic ointments. This study aimed to investigate and identify effective ointments to treat burn wounds. For this purpose, the effects of two types of ointment, fundermol and 1% silver sulfadiazine cream on second degree burn wounds were compared. METHODS: This was a clinical trial study conducted in 2008. Using convenient and continuous sampling method, 50 patients referred to Imam Mousa Kazem Burn Injury Clinic in Isfahan, Iran with 2nd degree burn wounds in 1% to 10% surface area were enrolled. The patients were randomly divided into two groups of treatment with fundermol and sulfadiazine and the dressing was changed once a day. The healing time for burn wounds in each patient was recorded in a checklist and data were analyzed by independent t-test via SPSS software. RESULTS: The healing time of burn wounds in the group treated with fundermol was shorter than that in the group treated with sulfadiazine (p < 0.001). CONCLUSIONS: The present study showed that fundermol ointment accelerates burn wound healing. Therefore, fundermol can be introduced as a good replacement for current treatments of burn wounds

Surface temperature measurements using a thin film thermal array

A thin film device was designed and fabricated to measure surface temperatures. An array of eight integrated thermal sensors are mounted on a 0.002 inch (0.05 mm) Kapton film and multiplexed to obtain an area thermal measurement. The device was tested on a flat plate airfoil and demonstrated a temperature variation of 0.55 C maximum and 0.05 C minimum compared to embedded thermocouples. Future improvements are also discussed

Emissivity Results on High Temperature Coatings for Refractory Composite Materials

The directional emissivity of various refractory composite materials considered for application for reentry and hypersonic vehicles was investigated. The directional emissivity was measured at elevated temperatures of up to 3400 F using a directional spectral radiometric technique during arc-jet test runs. A laboratory-based relative total radiance method was also used to measure total normal emissivity of some of the refractory composite materials. The data from the two techniques are compared. The paper will also compare the historical database of Reinforced Carbon-Carbon emissivity measurements with emissivity values generated recently on the material using the two techniques described in the paper

Thermal conductivity of refractory glass fibres

In the present study, the current international standards and corresponding apparatus for measuring the thermal conductivity of refractory glass fibre products have been reviewed. Refractory glass fibres are normally produced in the form of low-density needled mats. A major issue with thermal conductivity measurements of these materials is lack of reproducibility in the test results due to transformation of the test material during the test. Also needled mats are inherently inhomogeneous, and this poses additional problems. To be able to compare the various methods of thermal conductivity measurement, a refractory reference material was designed which is capable of withstanding maximum test temperatures (1673 K) with minimum transformation. The thermal conductivity of this reference material was then measured using various methods according to the different standards surveyed. In order to compare different materials, samples have been acquired from major refractory glass fibre manufacturers and the results have been compared against the newly introduced reference material. Materials manufactured by melt spinning, melt blowing and sol–gel have been studied, and results compared with literature values

PATIENT EDUCATION ABUOT SELF CARE KNOWLEDGE IN CHF PATIENTS

Introduction. Cardiovascular disease are the major cause of mortality in developed countries. CHF is also a chronic cardiovascular disorder. Teaching the self care plays a major role in its prevention and chronic complications. Regarding the importance of self care investigating the, effect of self care education on the knowledge of the patients on CHF is so important.&#13; Methods. In this study 42 patients with CHF were selected in the first exam held 15 days before and after a two hour training class. A training booklet was given to them. Data was collected by a questionnarie which includ 5 section as follows. The 1st section included the demographic charactristics. The 2nd section, 7 questions about anatpmy and physiology of the heart, the 3rd section included eight questions about drugs history, the 4th section included nine questions about regimen of the patients and the 5th section included 6 questions about physical activity.&#13; Results. The self care knowledge of patients increased 95 percent after education. There was no correlation between the effects of self care education and the age of all units studied. Statistical tests showed no correlation between the effects of self care education and educational level.&#13; Discussion. The knowlegde of the patients is low regarding the self care. The self care education to patients is the main duty of nurses. So, it is recommended to be considered as the first nursing intervention regarding these patients