Modeling heat exchange in recovery direct-flow boiler of auxiliary power plant based on organic Rankine cycle

Currently, there are many ways to improve the energy efficiency of different technological processes. The article presents the results of heat transfer simulating in a recovery direct-flow boiler of a ship auxiliary power plant using the organic Rankine cycle. There has been illustrated the basic circuit of the organic Rankine cycle unit. The parameters of the studied working bodies (pentane, ethanol, methanol) have been given. The process of the coolant boiling (for methanol) is considered, the process (5 s) of the coolant boiling from the liquid state to the steady state is modeled. There are presented the graphs of the dependence of the heat transfer coefficient on the length of the evaporator tube, on the specific heat of vaporization, on the surface tension, on the physical properties of the heat carrier material. There have been summarized the results of studying the dependence of the heat transfer coefficient during organic coolant boiling on such physical properties of the coolant as heat of vaporization and surface tension. Obtaining a numerical dependence that allows to calculate the heat transfer coefficient during the boiling of organic heat carriers, taking into account the physical properties of these heat carriers has been analyzed. The study was carried out by creating a numerical model of the evaporator in the ANSYS Fluent software. It has been found out that with the increasing ratio of the surface tension force to the specific heat of vaporization, the heat transfer coefficient increases. The empirical equation was also obtained for calculating the heat transfer coefficient during the organic heat carrier boiling.

Prediction of Liquid Molar Volume and Heat of Vaporization of Fatty Acids Using an Equation of State

Background:: The liquid molar volume (V) and the heat of vaporization (ΔHVAP) of four fatty acids (n-Heptanoic acid, Hexadecanoic acid, n-Hexanoic acid and n- Dodecanoic acid) have been estimated. Objective:: This paper aims to calculate the liquid molar volume and the heat of vaporization of four fatty acids under the critical point using two traditional equations of state: Peng-Robinson (PR) [21] and Soave-Redlich-Kwong. Methods: The area rules method applicable to obtaining the saturation pressure of the compounds has been used. The properties of the acids investigated in this work have been compared with those provided by literature. For molar volumes, the equations of state have given improved predictions when compared to traditional equations such as Rackett equation and so on. According to the vapor enthalpy calculations, no reference value was required. Results: In general, the Clausius-Clapeyron equation provides a better estimation of the vaporization enthalpy of fatty acids when Soave-Redlich-Kwong (SRK) equation was used. The heat of vaporization for fatty acids can be calculated with good reliability in comparison with the Watson equation if suitable equation of state is used. Conclusion: Accurate results for heat of vaporization can be reached in comparison with the Watson equation if the reliable equation of state is used.

Equilibrium Moisture Characteristics of Egg White Powder at Higher Temperatures

The equilibrium moisture content (EMC) of food material is defined as the moisture content of the material after it has been exposed to a particular environment for an infinitely long period of time. Equilibrium moisture characteristics of Egg White Powder (EWP) was studied at higher temperatures of 50, 60, 70, 80 and 90°C in the equilibrium relative humidity (ERH) range of 10-78% (at seven levels). The standard gravimetric method was used to determine the EMC-ERH relationships of EWP by employing the various saturated inorganic salt solutions. The EMC of EWP at any particular ERH decreased with an increase in environmental temperature. The EMC of EWP ranged from 2.17 to 3.35 at lower ERH value of about 10% whereas the EMC values ranged from 12.07 to 14.80 at higher ERH value of about 78% when the environmental temperature increased from 50°C to 90°C. EMC values of EWP are different than that of the values obtained at lower temperatures, hence useful to understand the thermal processing of EWP at higher temperatures. EMC-ERH data obtained in this study was fit into seven EMC-ERH models namely Henderson, modified Henderson, modified Chung-Pfost, modified Oswin, modified Halsey, modified GAB (Guggenheim, Ander-son and de-Boer) and Chen-Clayton models and were evaluated using mean relative percent error (Pe), standard error of estimate (SEE) and residual plots. The modified Henderson equation described the EMC-ERH relationship of EWP the best, Henderson, and Chen-Clayton equations gave good fit. The heat of vaporization (hfg) of EWP at different moisture contents and temperatures was calculated from EMC-ERH data with the help of the Clausius-Clapeyron equation. The hfg values indicate that the heat of vaporization of EWP increases as the moisture content and temperature decreases and the values are higher than that of the pure water.

Clarification on “Critical Comments on ‘Assessment of the Thermodynamic Properties of DL-p-Mentha-1,8-diene, 4-isopropyl-1-methylcyclohexene (DL-Limonene) by Inverse Gas Chromatography (IGC)’”

A clarification is given regarding recent polemic over our original published study. The author of this polemic has claimed a few issues about the computations and data listed in our work such as choosing the wrong temperature unit and the incorrect calculation of molar heat of vaporization. Here it is elaborated the complete data and computations that are not included in the original paper, and list out also the parameters, which may be the source of difference in reported molar heat of vaporization through inverse gas chromatography methods and other conventional methods. It is showed that there are no wrong calculations or reports of molar heat of vaporization in our published paper.