International Journal of Thermodynamics

At our laboratory extensive research has been conducted on the conversion of conventional Diesel cogeneration engines to operation on natural gas and biogas. In the framework of this research, a numerical simulation of a prechamber autoignition gas engine has been performed based on an experimental test case. With a simplified finite-rate/eddy-dissipation model for the combustion of natural gas, it was possible to properly reproduce the experiment considering the combustion duration, ignition timing and overall energy balance. A modification of the original cylindrical-conical prechamber geometry to a simpler cylindrical one was tested with the simulation model. The influence of burnt gases inside the prechamber was assessed simulating the mixture formation inside the prechamber. The simulations showed little effect of taking into account the non-homogeneities in the gas phase on the combustion duration. The new cylindrical geometry envisaged did not show any improvement in the combustion homogeneity inside the prechamber and its volume (limited by the real engine geometry) is in fact not sufficient to properly ignite the main chamber according to the simulations. The model can be used to further guide design modifications of the prechamber engine to improve performance.

The performance of sugar cane bagasse boilers is commonly analyzed through the first law of thermodynamics, using the energy balance method and the fuel lower heating value as calculation base. This work presents a first law analysis using two different methods: the input/output and the energy balance. The employment of the fuel higher and lower heating values as calculation base are presented and discussed. Moreover, a second law analysis is showed, based on two methods: input/output and exergy balance. The methods based on exergy concept permits to observe the main irreversibilities that happen during the steam production in a bagasse boiler.

The variety of radiographic diagnostic used to diagnose pain localised close to metal implants is still limited. Especially magnetic resonance results can not be analysed because of artefacts. In this article we present for the first time a direct correlation between an increase in skin temperature and existent anterior knee pain after total knee arthroplasty (TKA) measured with thermography.

In a standardised way 26 knees were analysed. Thermographic photos were taken from frontal, medial and lateral directions with a computer-assisted infrared thermograph. In medial location (median 0.95 °C, p=0.0043), as well as in lateral location (median 0.5 °C, p=0.032) temperatures in locations with pain were significantly higher compared to the reference field. Median temperature difference between pain localization and localizations without pain was 0.7 °C and ranged from 0.1 °C to 1.7 °C on the side of the pain. In the ROC analysis the sensitivity of this method was 1.0 and specificity was 0.917. The evidence of a significant increase in skin temperature on the painful sites opened up the possibility to localize and assess pain more precisely in patients with total knee prosthesis. We consider this novel, rapid, inexpensive and non-invasive technology to posses the potential to become a useful and objective tool for diagnosis of pain and inflammation and to generate digital data that can be stored and analysed in clinical practice.

A parametric study of the effects of binary interaction parameter and real-gas equations of state on the high pressure vapor-liquid equilibrium of nitrogen-n-dodecane system was carried out. Different values of the binary interaction parameter reported in literature, including one which depends on temperature, were employed in different equations of state to predict the vapor-liquid equilibrium as a function of ambient pressure and temperature. The findings were compared against the available experimental values reported in literature. Constant values of binary interaction parameter, estimated based on temperature dependent values, are demonstrated to predict the experimentally observed vapor-liquid equilibrium values accurately. The Peng-Robinson equation of state and an average binary interaction parameter were demonstrated to predict the vapor-liquid equilibrium over a wide range of temperature and pressures for nitrogen-n-dodecane binary system.

Viscosity and surface tension of upper critical solutions (UCS) of water + phenol with ΔG > 0 are reported. The phenol upper critical solutions within before (B) and after (A) UCS temperatures range are depicted as BUCS and AUCS respectively and were used for study. Viscous flow times (t, sec) and pendant drop numbers (n) were measured together with Survismeter for h/N m s^-2 and g/mN m^-1 respectively. The t and n were repeated for UCS with 0.5 millimol/L proteins (casein, pepsin, EA-Egg, albumin), vitamins [thiamine (B₁), riboflavin (B₂), pyridoxine (B₆)], amino acids (glycine, b-alanine, L-leucine), surfactants dodecyltrimethylammoniumbromide (DTAB), trimethylsulphoxoniumiodide (TMSOI), methyltrioctylammoniumchloride (MTOAC), orcinol and melamineformaldehyde-polyvinylpyrrolidone (MFP). Additives formed UCS at lower temperature with about 60% thermal energy saving. The t and n were used to calculate tn sec^-1 for density calculation with Mansingh equation. The BUCS, UCS and AUCS as pre UCS and post UCS were obtained at 60⁰C, 70⁰C and 61⁰C respectively. The tn with water were obtained for 25 to 70⁰C and plotted with corresponding densities (± 0.05 kg m^-3) for calibration curve used for density calculations. The densities were noted as TMSOI > orcinol > MFP > DTAB > MTOAC, with lower values at 66.5 and higher at 66⁰C.