A Comparative Investigation on Homogeneous Condensation of R600a and R134a using MD Simulations

Md. Sarwar Alam,Ji Hwan Jeong 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.4

MD simulation estimation of saturation pressure and vapor-liquid equilibrium for binary blends of HFO-1234yf and HFO-1123

Alam Md. Sarwar,정지환 대한설비공학회 2022 International Journal of Air-Conditioning and Refr Vol.30 No.1

Saturation pressure and vapor-liquid equilibrium data of low GWP hydrofluoroolefin compound HFO-1234yf (2,3,3,3-tetrafluoropropene) and its binary blends with HFO-1123 (1,1,2-trifluoroethene) were estimated using molecular dynamics (MD) simulation with the aid of COMPASS force field from 214.15 K to 330.15 K. The maximum absolute deviations of present saturated vapor pressure data from published experimental results were 0.03% for HFO-1123 system and 0.017% for HFO-1234yf system. These models were used to estimate the saturated vapor pressure for six different mixtures of HFO-1234yf and HFO-1123. The saturated liquid and vapor densities, the vapor-liquid coexistence curve (VLCC), and the critical points of the blended refrigerants with various molecular mass fractions were predicted using MD simulations and Gibbs ensemble Monte Carlo (GEMC) simulations. The critical points of HFO-1234yf and HFO-1123 matched well with published data.

분자동역학 해석을 이용한 다양한 응축온도에서 R448A와 R449A의 상변화 및 열물성 평가

Md. Sarwar Alam,김태열,정지환 대한설비공학회 2022 설비공학 논문집 Vol.34 No.5

Molecular dynamics simulations are performed to evaluate phase transition phenomena, liquid density, shear viscosity, and the isobaric heat capacity of low GWP refrigerants R448A and R449A. Increasing the condensing temperature from 273.15 K to 298.15 K leads to increase in the phase change duration of R448A and R449A. Moreover, the liquid density decreases to 11.24% for R448A, and 12.34% for R449A with the an increase in temperature from 273.15 K to 308.15 K. The particles’ snapshots reveal that vapor molecules undergo a rapid phase transition, to the subcooled liquid at a certain condensing time period. Subcritical clusters of R448A and R449A refrigerants’ molecules are formed in the initial part of the simulations, which then aggregate to produce the critical condensate nucleus over time. The liquid density, shear viscosity, and isobaric heat capacity of the two refrigerants predicted by the present MD simulations agree well with data of REFPROP. 새로운 냉매의 상변화 과정과 열물성은 냉동시스템 성능을 분석하는 데 필수적이다. 본 연구에서는 분자동역학 시뮬레이션을 사용하여 온도 273.15 K, 298.15 K, 303.15 K, 308.15 K에서 냉매의 상변화 과정과 열물성을 해석하였다. 혼합냉매인 R448A와 R449A 과열증기가 응축되는 과정을 해석하여 균질상변화 과정 및 열물성을 평가하였다. 증기 분자의 무작위 충돌은 클러스터를 생성하고, 클러스터들이 뭉쳐서 액적을 형성하였다. 냉매 시스템의 평균밀도는 초기에 서서히 증가하다가 특정 시간에 급속히 증가하였고, 이후 안정하게 유지되었다. MD 해석을 통해 혼합냉매의 기상 및 액상 밀도, 점도, 열용량(비열)을 예측할 수 있었고, 이 값들은 REFPROP의 혼합물 예측방법으로 계산된 값들과 잘 일치하였다. 이러한 결과는 향후 새로운 혼합냉매 개발시, MD 해석으로 열물성을 미리 예측해 볼 수 있음을 증명하고 있다.

Analysis of phase transition, structural and dynamical properties of R290 using molecular dynamics simulation

Md. Sarwar Alam,Ji Hwan Jeong 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.10

Propane (R290), a hydrocarbon refrigerant, is an excellent choice of cooling fluids for use in refrigeration and air conditioning systems considering the environmental point of view and system performance. The phase transition phenomenon and structural and dynamic properties of R290 were analyzed through a molecular dynamics (MD) simulation. The densities, isobaric heat capacities and viscosities were computed and the variations of density, volume, potential energy and the nucleation process were examined to investigate the effects of condensation temperature on the phase transition rate. The mean square displacement and velocity autocorrelation function for different temperatures were simulated for dynamical analysis. Radial distribution functions were investigated to get insight into the structural analysis at the atomic level. Shear viscosity and isobaric heat capacity obtained by the present simulation showed a good agreement with the REFPROP data. The structural analysis revealed that the phase transition of R290 did not affect its intramolecular structure.

Molecular dynamics simulations on homogeneous condensation of R600a refrigerant

Alam, Md. Sarwar,Jeong, Ji Hwan Elsevier 2018 Journal of molecular liquids Vol.261 No.-

<P>Molecular Dynamics (MD) simulations have been employed to study the homogeneous condensation phenomenon of R600a (isobutane) refrigerant in the vapor compression refrigeration system. The molecular system consists of superheated vapor isobutane in a cuboid simulation cell with periodic boundary conditions in all directions. A more physically reliable thermostat and a barostat are applied to control the temperature and pressure of the cell containing the molecules. Based on AHRI standard 460 rating conditions, the simulations started from the initial configuration of vapor phase isobutane system, and once the equilibration is established at 361 K with 1 atm, the system is suddenly cooled to the ambient temperature of 308 K and is set under the condensing pressure of 7.1658 bar corresponding to the saturation temperature at 325 K of the compound at supersaturation ratio 1.548. The density, internal potential energy, and volume changing with time of superheated vapor molecules in the homogeneous condensation process of the system are investigated. The results show that vapor molecules have underwent a rapid phase transition to the subcooled liquid at a certain critical time period. Subcritical clusters of isobutane molecules are formed in the preliminary part of the simulations, which then aggregate to generate the critical condensate nucleus over time. An examination of the radial distribution functions (RDFs) shows that the bonding and non-bonding interactions are formed in the vapor and liquid phases of isobutane. It is truly consistent with the internal potential energy and phase change properties. The computed densities of both phases agree well with the NIST standard reference thermodynamic and transport property data of the compound. A comparative study is executed through several simulations for various values of supersaturation and undersaturation ratios with different numbers of molecules to investigate the critical time of phase transition in the homogeneous condensation process. (C) 2018 Elsevier B.V. All rights reserved.</P>

Comparative molecular dynamics simulations of homogeneous condensation of refrigerants

Alam, Md. Sarwar,Jeong, Ji Hwan Elsevier 2019 INTERNATIONAL JOURNAL OF THERMAL SCIENCES Vol.141 No.-

<P><B>Abstract</B></P> <P>Performance improvement and environmental impact are very important issues in the selection of suitable refrigerant for domestic refrigeration systems. The homogeneous condensation of two hydrocarbon (HC) refrigerants, namely, R600 (butane) and R600a (isobutane) and two hydrofluorocarbon (HFC) refrigerants i.e. R134a (1,1,1,2-tetrafluoroethane) and R143a (1,1,1-trifluoroethane) was investigated by molecular dynamics simulations. The thermophysical properties of the four refrigerants, such as the density, internal potential energy, and cell volume of the molecular systems during the condensation process are compared. The influences of the various refrigerants on the potential energy and the cluster formation are described. The results show that vapor molecules undergo a rapid phase transition to a subcooled liquid within a specific time period. In the simulations, clusters of the substances are formed initially, which then aggregate to produce the condensate liquid droplets over time. The densities of all the refrigerants at the liquid phase after condensation agree with REFPROP data. A comparative analysis of the refrigerants was performed based on the saturation ratio to investigate the time of complete condensation in the homogeneous condensation process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> R600a (isobutane) is widely used as a refrigerant of domestic refrigerators. </LI> <LI> Molecular dynamics simulations for condensation of HC and HFC refrigerants. </LI> <LI> Computed properties are in good agreement with NIST property table. </LI> <LI> Critical time of phase transition in the condensation process was compared. </LI> </UL> </P>

Thermodynamic properties and critical parameters of HFO-1123 and its binary blends with HFC-32 and HFC-134a using molecular simulations

Alam, Md. Sarwar,Jeong, Ji Hwan IPC Science and Technology Press 2019 International journal of refrigeration Vol.104 No.-

<P><B>Abstract</B></P> <P>The hydrofluoroolefin (HFO) refrigerant 1,1,2-trifluoroethene (HFO-1123, CF2=CHF) and its blends are considered next-generation refrigerants due to their zero ozone depletion potential (ODP) and low global warming potential (GWP). In this study, the saturation pressures of HFO-1123 and its binary blends difluoromethane (HFC-32) + 1,1,2-trifluoroethene (HFO-1123) and 1,1,1,2-tetrafluoroethane (HFC-134a) + 1,1,2-trifluoroethene (HFO-1123) under various compositions are computed in the temperature range of 230–330 K using a first ab initio COMPASS force field in molecular dynamics simulations. The estimates of other thermodynamic properties, such as the saturated densities of the pure compounds and their binary blends are provided to supplement experimental data. Moreover, the critical points of HFO-1123 and its binary blends with various compositions, along with their disparities, are also estimated.</P>

Molecular dynamics simulations of homogeneous condensation and thermophysical properties of HFO1123 and its binary blends with HFC134a at 273.15 K to 298.15 K

Md. Sarwar Alam,정지환 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.5

The hydrofluoroolefin (HFO) refrigerant R1123 (1,1,2-trifluoroethene) and its blends with R134a are excellent alternative choices for refrigeration systems, considering environmental issues and system performance. Molecular dynamics (MD) simulations were performed to investigate the homogeneous condensation process and to predict the density and isobaric heat capacity of pure R1123 and its binary blends with R134a. The condensation rate of pure R1123 and the (R1123+R134a) blends was higher at lower condensation temperatures. The vapor molecules went through a rapid phase transition to a subcooled liquid state during a particular time period, and the potential energy of the molecular systems was drastically reduced at this time. During condensation, clusters of molecules were initially formed, and they subsequently aggregated to develop a condensate droplet. The liquid density and isobaric heat capacity of pure R1123 and its four blends were predicted for the temperature range of 273.15 K to 298.15 K.

Morphology, Morphometry, Growth Performance and Carcass Characteristics of Pekin, Nageswari and Their F₁ Crossbred Ducks under Intensive Management

Md. Tanvir Ahmad,Drishti Nandita,Tanvir Mohammad Maruf,Mohammad Hasanuzzaman Pabitra,Sabrina Islam Mony,Md. Shawkat Ali,Md. Sarwar Ahmed,Mohammad Shamsul Alam Bhuiyan 한국가금학회 2021 韓國家禽學會誌 Vol.48 No.2

This study investigated the morphological features, growth, and meat yield performance of Pekin (P), Nageswari (N), and their reciprocal F1 crossbreds (P♂×N♀ and N♂×P♀). A total of 301-day-old ducklings were reared in four different pens up to 20 weeks of age under intensive management conditions. Feeding and management practices were similar for all individuals throughout the experimental period. The morphology and plumage pattern of F1 crossbreds were similar to those of indigenous Nageswari ducks because of the dominant inheritance of the extended Black allele (E locus). Genotype had significant differences (P<0.05) among the four genotypes in morphometric measurements, except wing and shank length. Growth performance was highly significant among the four genotypes (P<0.001) from one-day to 12 weeks of age. The average live weights of P, N, P♂×N♀ and N♂×P♀ crossbred genotypes at 12 weeks of age were 2038.35±29.74, 1542.44±33.61, 1851.85±28.59 and 1691.08±27.80 g, respectively. Meat yield parameters varied significantly (P<0.05) among the different genotypes for all studied traits, except for liver and gizzard weight. Moreover, no significant differences (P>0.05) were observed between P and P♂×N♀ crossbred for important meat yield traits such as hot carcass weight, dressing%, back half weight, drumstick with thigh weight and breast meat weight. Remarkably, the P♂×N♀ crossbreed possesses 50% native inheritance, which contributes to better adaptation in a hot-humid environment. Our results revealed that the P♂×N♀ genotype could be suitable for higher meat production with better adaptability in the agro-climatic conditions of Bangladesh.

Vapor-liquid phase transition behavior and thermophysical properties of R448A and R449A at temperatures from 233.15 K to 308.15 K

Md. Sarwar Alam,정지환 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

The present work uses molecular dynamics simulation to investigate the phase transition phenomena, saturated vapor-liquid density, shear viscosity, isobaric heat capacity, and velocity auto correlation function of low GWP refrigerants R448A and R449A at various temperatures. The phase change behavior of the refrigerants is investigated through the density profile and potential energy distribution; the dynamical behavior is examined according to the condensate period, molecular aggregation in the trajectory, and velocity auto correlation function of the condensed particles. The results show that increasing the condensing temperature from 233.15 K to 308.15 K leads to slow phase transitions for both R448A and R449A. The liquid density of R448A decreases to 19.21 % and its vapor density increases to 13.07 %, while the liquid density of R449A decreases to 19.59 % and its vapor density increases to 12.64 % due to the increase of temperature from 233.15 K to 308.15 K. Particle snapshots reveal that vapor molecules underwent a quick phase transition to subcooled liquid during a certain condensing time period. Subcritical clusters of both R448A and R449A refrigerant molecules are shaped in the initial part of the simulations, and then aggregate to produce critical condensate nuclei over time.