Normal Boiling Point Temperature Research Articles

Thermodynamic Study of N-Methylformamide and N,N-Dimethyl-Formamide.

An extensive thermodynamic study of N-methylformamide (CAS RN: 123-39-7) and N,N-dimethylformamide (CAS RN: 68-12-2), is presented in this work. The liquid heat capacities of N-methylformamide were measured by Tian-Calvet calorimetry in the temperature interval (250-300) K. The vapor pressures for N-methylformamide and N,N-dimethylformamide were measured using static method in the temperature range 238 K to 308 K. The ideal-gas thermodynamic properties were calculated using a combination of the density functional theory (DFT) and statistical thermodynamics. A consistent thermodynamic description was developed using the method of simultaneous correlation, where the experimental and selected literature data for vapor pressures, vaporization enthalpies, and liquid phase heat capacities and the calculated ideal-gas heat capacities were treated together to ensure overall thermodynamic consistency of the results. The resulting vapor pressure equation is valid from the triple point to the normal boiling point temperature.

An International Standard Formulation for trans-1-Chloro-3,3,3-trifluoroprop-1-ene [R1233zd(E)] Covering Temperatures from the Triple-Point Temperature to 450 K and Pressures up to 100 MPa

A new Helmholtz energy equation of state is presented for trans-1-chloro-3,3,3-trifluoroprop-1-ene [R1233zd(E)], which is expressed with temperature and density as independent variables. Experimental data in the range of temperatures from 215 to 444 K and pressures up to 35 MPa form the basis of the new equation. In this range, expected uncertainties (k = 2) of the new equation of state are 0.07% for vapor pressures at temperatures above the normal boiling point temperature (≈291K), 0.2% for vapor pressures at lower temperatures, 0.05% for liquid densities, 0.15% for vapor densities, 0.1% for saturated liquid densities, 0.05% for liquid-phase sound speeds, and 0.08% for vapor-phase sound speeds. The new equation is valid at temperatures from the triple-point temperature (165.75 K) to 450 K and pressures up to 100 MPa with reasonable uncertainties outside the available range of data because it fully extrapolates with correct physical behavior to higher temperatures and pressures as well as to lower temperatures. The equation of state presented here has been recommended as an international standard by the working group presently revising ISO 17584 (Refrigerant Properties).

New empirical correlations for the prediction of critical properties and acentric factor of S-containing compounds

In the present study, simple empirical correlations have been developed to estimate the critical properties (i.e. TC, PC, and VC) and acentric factor (ω) of S-containing compounds. The variables of correlations are a set of simple parameters, including normal boiling point temperature (Tb), molecular weight (MW), and the number of atoms and bonds. A comprehensive dataset containing more than 130 S-containing compounds, including thiophenes, sulfides, mercaptans, siloxanes, and others, has been used for the model development. The parameter selection of the models has been carried out using the Enhanced Replacement Method. Two specific linear and non-linear models have been separately developed for each critical property and ω. The genetic programming method was applied for the development of the non-linear model. Statistical evaluation of the developed models confirmed the satisfactory capability of the models to predict the critical properties and ω of new compounds. Indeed, the values of the coefficient of determination (R2) of the non-linear models for TC, PC, VC, and ω were 0.9690, 0.9076, 0.9890, and 0.9467, respectively. In addition, the values of the average absolute relative deviation (AARD%) of the non-linear models for TC, PC, VC, and ω were 2.1677, 7.8375, 3.8919, and 9.9344, respectively.

Thermodynamic comparison of modified Rankine cycle configurations for LNG cold energy recovery under different working conditions

In this study, we present the evaluation of two modified single-stage Rankine cycles (RC) and two two-stage RCs to provide a guidance for configuration selection under different working conditions. Moreover, a regenerative-reheat RC, which is the combination of the modified single-stage RCs, is proposed to utilize the cold energy of liquefied natural gas (LNG) and the thermal energy of low grade heat. The key parameters of these five configurations using eight working fluids are optimized with exergy efficiency as the optimization objective. The results show that the modified single-stage RCs are usually better than the two-stage RCs since they have simpler configurations with similar or higher efficiencies. The regenerative-reheat RC performs even better under most working conditions and it achieves the maximum efficiency of 24.57% by using ethane as the working fluid under the heat source temperature of 180 °C and the pipeline pressure of 3 MPa. The addition of direct expansion cycle can improve the exergy efficiencies of most fluids and configurations under lower pipeline pressures. However, the improvements decrease greatly for fluids with low normal boiling point temperatures (NBPTs) and especially under higher pipeline pressures. As to the fluid selection, high critical temperature and low NBPT are both important for reheat RC and parallel two-stage RC. NBPT weights more than critical temperature for regenerative RC and regenerative-reheat RC. Besides, wet working fluids are more suitable for reheat RC while dry and isentropic fluids are more suitable for regenerative RC and regenerative-reheat RC. The optimal regenerative ratio and reheat pressure ratio vary with different working fluids and working conditions. Lower reheat pressure ratio usually leads to higher regenerative ratio.

New structure-based models for the prediction of normal boiling point temperature of ternary azeotropes

Recently, development of the QSPR models for mixtures has received much attention. The QSPR modelling of mixtures requires the use of the appropriate mixture descriptors. In this study, 12 mathematical equations were considered to compute mixture descriptors from the individual components for the prediction of normal boiling points of 78 ternary azeotropic mixtures. Multiple linear regression (MLR) was employed to build all QSPR models. Memorized_ ACO algorithm was employed for subset variable selection. An ensemble model was also constructed using averaging strategy to improve the predictability of the final QSAR model. The models have been validated by a test set comprised of 24 ternary azeotropes and by different statistical tests. The resulted ensemble QSPR model had R2 training, R2 test and q2 of 0.97, 0.95, and 0.96, respectively. The mean absolute error (MAE), as a good indicator of model performance, were found to be 3.06 and 3.52 for training and testing sets, respectively.

Fatty Acid Content in Biomasses: State-of-the-Art and Novel Physical Property Estimation Methods

In line with the growing environmental awareness developed along the last decades, modern societies are urged to evolve into sustainable economics where the reuse of organic wastes represents the key feedstock for a green transaction. The oil phase obtained from different biomasses has the potential to be a source of food supplements, medicines, cosmetics, or feedstock for biofuel production. In the present work, the composition of 104 different biomasses including seeds, peels, flowers, plants, and leaves has been reviewed for the lipid content. Based on the most frequent fatty acids screened, experimental data for normal boiling point temperature, normal melting point, critical properties, and acentric factor were collected and compared with the most common estimation methods, which are functions of the molecular structure and interaction between different functional groups. New predictive equations have been proposed to reduce the estimation deviation and to provide simple correlations to be used in simulation software when dealing with biomass processes. For all the properties, the estimations proposed have an absolute average deviation equal to or lower than 4.6%.

QSPR estimation models of normal boiling point and relative liquid density of pure hydrocarbons using MLR and MLP-ANN methods

This work aimed to predict the normal boiling point temperature (Tb) and relative liquid density (d20) of petroleum fractions and pure hydrocarbons, through a multi-layer perceptron artificial neural network (MLP-ANN) based on the molecular descriptors. A set of 223 and 222 diverse data points for Tb and d20 were respectively used to build two quantitative structure property relationships-artificial neural network (QSPR-ANN) models. For each model, the total database was divided respectively into two subsets: 80% for the training set and 20% for the test set. A total of 1666 descriptors were calculated, and the statistical reduction methodology, based on the Multiple Linear Regression (MLR) method, has been adopted. The Quasi-Newton back propagation (BFGS) algorithm was applied in order to train the ANN. A comparison was made between the outcomes of obtained QSPR-ANN models and other well-known correlations for each property. The two best QSPR-ANN models result showed a good accuracy confirmed by the high determination coefficient (R2) values and the low mean absolute percentage error (MAPE) values ranging from 0.9999 to 0.9931 and from 0.5797 to 0.2600%, respectively for both best models (Tb and d20 models). Furthermore, the comparison between our models and the other quantitative structure property relationships (QSPR) models shows that the QSPR-ANN models provided better results. This computational approach can be applied in the petroleum engineering for an accurate determination of Tb and d20 of pure hydrocarbons.

Critical Assessment of Using an Ionic Liquid as Entrainer via Extractive Distillation

Ionic liquids (ILs) have received much attention in the last two decades. One of the important applications is to use this relatively new class of compounds for the separation of azeotropic mixtures via extractive distillation. In this paper, overall extractive distillation processes of two azeotropic separation systems using a favorable ionic liquid as entrainer are rigorously developed. The optimized design flowsheets are compared with the conventional processes using an industrial entrainer. The two ionic liquid extractive distillation systems include separating acetone and methanol using 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) as entrainer and another system of separating isopropyl alcohol and water using 1-ethyl-3-methylimidazolium acetate ([EMIM][OAC]) as entrainer. The potential drawbacks of using an ionic liquid in the extractive distillation systems are given in the paper. It is found that the degradation temperature and high normal boiling point temperature of the ionic liquids i...

Saturated Pressure Measurements of trans-1-Chloro-3,3,3-trifluoroprop-1-ene (R1233zd(E))

Hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs) are two of the most promising families of low-GWP fluids being investigated as alternatives for HFCs in HVAC&R applications. Within the HCFO family, trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) is a compound with a relatively high normal boiling point temperature (∼291.1 K) and was developed primarily as a blowing agent for polymer foams, a low-pressure refrigerant for chiller applications, and a working fluid for low-temperature ORC applications. This article presents 81 vapor pressure data points measured over the temperature range from (234.15 to 375.15) K in two different laboratories. The data are fitted to Wagner-type and Antoine-type equations and compared to existing correlations and other published data.

Comprehensive study on the role of eco-friendly working fluid properties on ORC performances

In the present study, the effects of various low-GWP fluid properties on organic Rankine cycle (ORC) performances are examined for low grade heat sources and an attempt is made to prepare a general guideline to compare working fluids for ORC based on their basic properties. Theoretical study on ORC is conducted to study the effects of various fluid properties on net power generation, thermal efficiency, turbo-machinery and heat exchanger compactness. The considered eco-friendly working fluids for ORC were shortlisted based on operational, environmental and safety criteria. Performance comparison between selected working fluids shows that ammonia is the best fluid in terms of net power generation and compactness of turbo-machineries, whereas n-Pentane is the best fluid in terms of thermal efficiency and heat exchangers compactness. Study shows that the molar mass, normal boiling point temperature, critical temperature and phase diagram characteristics have significant effect on cycle performance indexes. However, the effect of properties does not show any common criteria for best in terms of all performance indexes. Present study summarizes the required fluid properties to get individually best for all performance indexes, which will be useful for fluid comparison and selection for certain design target.

A GEP based model for prediction of densities of ionic liquids

Abstract One of the most important properties of ionic liquids (ILs) is their densities. Accurate knowledge of this property is required in engineering and scientific purposes including equipment design, liquid metering calculations, and other applications. As a result, it is important to develop accurate and effective models for prediction of this property. The present work aims to develop a model based on Gene Expression Programming (GEP) technique for prediction of experimental density values of 146 different ionic liquids at different temperatures. A databank containing 602 data gathered from the literature was utilized to develop the model. The input parameters of the model are temperature, molecular weight of IL, normal boiling point temperature of IL, critical pressure of IL, critical volume of IL, and acentric factor of IL. The outcomes of this work indicate that the developed model is capable of estimating target density data with an acceptable accuracy. The effectiveness and accuracy of the model were checked by utilizing different statistical and graphical techniques. Moreover, results of the proposed model are compared with predictions of literature correlations and it is shown that the GEP model is effectively superior to other correlations and exhibits higher accuracy and reliability.

Property-based selection criteria of low GWP working fluids for organic Rankine cycle

In the present study, an attempt is made to prepare a general guideline to compare and select the suitable working fluids for organic Rankine cycle based on their basic properties without going through rigorous numerical or experimental study. Theoretical study on organic Rankine cycle for two low grade sensible heat sources is conducted to study the effects of various fluid properties (molar mass, chemical composition, acentric factor, fluid class, fluid type, freezing point temperature, normal boiling point temperature, critical temperature, critical pressure, molecular complexity, Jacob number, figure of merit and various proposed parameters for phase diagram characteristics) on net power generation, thermal and exergetic efficiencies, turbo-machinery and heat exchanger compactness. For this, the suitable working fluids for organic Rankine cycle have been shortlisted based on operational, environmental and safety criteria. Study shows that some fluid properties have significant effect on cycle performance indexes. However, the effect of properties does not show any common criteria for the best in terms of all performance indexes. Present study summarizes the required fluid properties to get individually best for all performance indexes, which will be useful for working fluid comparison and selection for certain design target.

Numerical study on performance of perforated plate applied to cryogenic fluid flowmeter

The perforated plate is one of the effective devices for measuring flow rate accurately. In this study, a perforated plate is investigated for its characteristics, mainly including discharge coefficient C and pressure loss coefficient ζ, when applied to cryogenic fluids with the help of ANSYS Fluent. Three cryogenic fluids are studied, including liquid nitrogen (LN2), liquid oxygen (LO2), and liquid hydrogen (LH2). For comparison, two states of water are also investigated. The realizable κ-e model with standard wall function is used to describe the turbulence and simulate the near-wall flow. The Schnerr-Sauer cavitation model is used to investigate the effect of cavitation on the performance of the perforated plate. Simulation results indicate that the upper limit of Reynolds number of the perforated plate is significantly dependent on the properties of the measured fluid when the temperatures of the fluids are set as the normal boiling point temperatures and the outlet pressures are 0.2 MPa.

Microwave-Assisted Superheating and/or Microwave-Specific Superboiling (Nucleation-Limited Boiling) of Liquids Occurs under Certain Conditions but is Mitigated by Stirring.

Temporary superheating and sustained nucleation-limited “superboiling” of unstirred liquids above the normal atmospheric boiling point have been documented during microwave heating. These phenomena are reliably observed under prescribed conditions, although the duration (of superheating) and magnitude (of superheating and superboiling) vary according to system parameters such as volume of the liquid and the size and shape of the vessel. Both phenomena are mitigated by rapid stirring with an appropriate stir bar and/or with the addition of boiling chips, which provide nucleation sites to support the phase-change from liquid to gas. With proper experimental design and especially proper stirring, the measured temperature of typical organic reaction mixtures heated at reflux will be close to the normal boiling point temperature of the solvent, whether heated using microwave radiation or conventional convective heat transfer. These observations are important to take into consideration when comparing reaction rates under conventional and microwave heating.

Vapor pressures and thermophysical properties of selected hexenols and recommended vapor pressure for hexan-1-ol

A thermodynamic study of selected unsaturated alcohols, cis-hex-3-en-1-ol, trans-hex-2-en-1-ol, and hex-1-en-3-ol, together with hexan-1-ol, is presented in this work. The vapor pressure measurements were performed using the static method over the environmentally important temperature range from 238 to 308K. Liquid heat capacities were measured by Tian–Calvet calorimetry in the temperature interval from 258 to 355K and were extended by controlled extrapolation by differential scanning calorimetry (DSC) toward the normal boiling point temperatures. The phase behavior was investigated by DSC from 183K. The thermodynamic properties in the ideal-gas state were calculated by combining statistical thermodynamics and density functional theory (DFT) calculations. Scaling factors were evaluated based on measured Raman and IR spectra. Calculated ideal-gas heat capacities and experimental data on vapor pressures, condensed phase heat capacities, and vaporization enthalpies were treated simultaneously to obtain a consistent thermodynamic description.

Prediction of Kinematic Viscosity of Petroleum Fractions Using Artificial Neural Networks

In this work, artificial neural network (ANN) was utilized to develop a new model for the prediction of the kinematic viscosity of petroleum fractions. This model was generated as a function of temperature (T), normal boiling point temperature (Tb), and specific gravity (S). In order to develop the new model, different architectures of feed-forward type were examined. Finally, the optimum structure with three hidden layers was selected. The optimum structure had five, four, and two neurons in the first, second, and third layers respectively. To prevent over-fitting problem, 70% of the experimental data were used to train and validate the new model and the remaining data which did not participate in learning process was utilized to test the ability of the new model for the prediction of the kinematic viscosity of petroleum fractions. The results showed that the predicted/calculated and experimental data are in good agreement. The average absolute relative deviation (AARD) of the new model was 1.3%. Finally, the results were compared with an Eyring-based model (Soltani et al.’s work); it was shown that, based on the reported results by the authors, the accuracy of both model were in the same order.

A Novel Equation of State: Determination and Validation for Dyes and Drugs Solubility Calculations in Supercritical Carbon Dioxide

Based on Pitzer correlations for the compressibility factor and virial equation of state, a new equation of state has been developed in this study, which is a function of total number of atoms present in the solute molecule, normal boiling point temperature and reduced temperature. Thirty dyes and sixty drugs solubility data, 2417 data points, have been collected from literature and compared with the Peng-Robinson EOS plus the two adjustable parameters van der Waals mixing rules, and the new proposed EOS. As the results show, the proposed EOS presents more accurate predictions for solubility data in Supercritical Carbon Dioxide.

Development of a quantitative structure–liquid thermal conductivity relationship for pure chemical compounds

In this study, a quantitative structure-liquid thermal conductivity relationship was developed for pure mostly organic chemical compounds. An extensive data set including more than 19,000 evaluated liquid thermal conductivity data for 1635 pure mostly organic chemical compounds at various temperatures and at atmospheric pressure below the normal boiling point and at saturated pressure above the normal boiling point temperature was provided from DIPPR 801 database to develop, validate and assess the predictive capabilities of the obtained correlation. Parameters of the model comprise 20 molecular descriptors including temperature. The obtained model shows a good agreement with DIPPR 801 data. The model shows the same values of the average absolute relative deviation and root mean square error of 7.4% and 0.01 for the training set (80% of the data), the validation set (10% of the data), and the test set (10% of the data). In terms of wide range of applicability, the model shows reasonable accuracy.

Prediction of Normal Boiling Points of Hydrocarbons Using Simple Molecular Properties

Four hundred and seventy-six hydrocarbons (CnHm )w ere utilized to fit their normal boiling point temperatures (NBPT) as a function of molecular weight and carbon atomic fraction. The proposed model is of the following form: NBPT=a ∗ (Cfrac) ∧ b ∗ (MW) ∧ c ,w here a, b ,a ndc are the non-linear regressed parameters for the given model; Cfrac is the carbon atomic fraction in a molecule, which is equal to n/(n+m) for a hydrocarbon compound; and MW is the molecular weight, which is calculated as 12 ∗ n+ 1 ∗ m. The model was found to predict NBPT with an adequate accuracy, manifested via the associ- ated percent relative error (PRE) of the curve-fitted NBPT. Out of the examined 476 hydrocarbons, methane, ethylene, and acetylene were found to have PRE values higher than 10%. If the confidence interval is further reduced to PRE value less than 5%, then 43 compounds will be excluded, and then NBPT for the other 433 compounds could be well predicted by the proposed model. Although the proposed model does not differentiate among isomers having the same molecular weight and chemical formula, nevertheless, the difference in NBPT among isomers is not really significant to be picked up by a simple, straight- forward model. A more rigorous model will work hard to offset such small differences in NBPT among isomers, nevertheless, at the expense of model simplicity.

Octanol/Air Partition Coefficients of Volatile Methylsiloxanes and Their Temperature Dependence

The octanol/air partition coefficient (KOA) is a key parameter used to predict the long-range transport potential (LRTP) of volatile and semivolatile organic compounds and their bioaccumulation in terrestrial biota. Despite the enormous importance of this parameter, reliable KOA values are not available for volatile methylsiloxanes (VMS). In this study, a method of syringe headspace analysis was developed to determine KOA values for six common VMS at trace levels. It was found that log KOA values of any given VMS were linearly related to the reciprocal of the environmental temperature (T) from −3 °C to 40 °C, whereas at any given T, the log KOA values of different VMS were linearly related to their molecular mass and normal boiling point temperatures (Tb). Based on those findings, empirical models were developed to predict log KOA values of methylsiloxanes using Tb (or molecular mass) and T as the only independent variables. The log KOA values for common VMS at 25 °C were in the range from 2.98 (for hexamethyldisiloxane) to 5.77 (for dodecamethylcyclohexasiloxane). Judging from the log KOA values, these VMS have little potential for long-range transport and deposition to remote surface media and for bioaccumulation in terrestrial biota.