利用简单的预测工具估算高压下的空气比热容比外文翻译资料

命名法

A

调谐系数

R

通用气体常数（R）8.314 J/(kmol K)

B

调谐系数

T

温度 （K）

C

调谐系数

特性极限温度 （K）

D

调谐系数

V

范德蒙德矩阵

定压比热(J/(kgK))

V

体积 （m³）

定容比热(J/(kgK))

x

多项式的自变量

E

引起参数变化的过程活化能(J/kmol)

alpha;

热膨胀系数

适当定义与温度有关的参数，为某一特性单独确定的单元

等温压缩性

指前系数，具有相同单位的利息性质

等熵可压缩性

P

压力（杆）

rho;

密度 (kg/m³)

kappa;

比热比，无量纲

psi;

多项式

系数

值

A₁

2.13879130290102times;10^-1

B₁

2.82131393663459times;10^-4

C₁

1.2488865910034times;10^-5

D₁

6.27433500214741times;10^-8

A₂

1.01842474952184times;10²

B₂

5.31113787399755times;10^-1

C₂

2.22974989456912times;10^-2

D₂

1.16407115910221times;10^-4

A₃

2.78259248326215times;10⁴

B<sub

剩余内容已隐藏，支付完成后下载完整资料</sub

Estimation of air specific heat ratio at elevated pressures using simple predictive tool

Keywords:

Formulation

Specific heat ratio

Compressed air

Vandermonde matrix

Arrhenius function

Over the years, considerable research effort has been expended towards evaluation of the thermophysical and transport properties of air for a wide range of temperatures. However, a relatively limited attention was oriented towards investigation of air specific heat ratios at elevated pressures. In this work, a simple predictive tool, which is easier than current available models, less complicated with fewer computations and suitable for process engineers, is presented here for the prediction of specific heat ratio of air at elevated pressures as a function of temperature and pressure using a novel and theoretically based meaningful Arrhenius-type asymptotic exponential function combined with Vandermonde matrix. The proposed method is superior owing to its accuracy and clear numerical background based on Vandermonde matrix, wherein the relevant coefficients can be retuned quickly if more data are available. The proposed correlation predicts the specific heat ratios of air for temperatures up to 1000 K, and pressures up to 1000 bar (100,000 kPa). Estimations are found to be in excellent agreement with the reliable data in the literature with average absolute deviations being less than 0.2%. The tool developed in this study can be of immense practical value for the engineers and scientists to have a quick check on the compressed air specific heat ratios at various conditions without opting for any experimental measurements. In particular, chemical and process engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions.

1.Introduction

The development of methods for evaluation of air properties was the subject of a number of earlier investigations, which were employed to conduct property evaluation calculations at specific temperature regions of interest in a certain range of scientific and technological applications, like metrology and calibration as well as for air conditioning ^[1]. These scientific fields of application and the corresponding investigations mainly refer either to low temperatures like those carried out by Giacomo ^[2,3], or to relatively higher temperatures as those by Melling et al.^[4], who investigated air properties in the temperature range between 100 and

200 °C. However, the knowledge of properties at wide range of temperature levels is vital for certain other technological fields, like drying, to allow accurate prediction of heat and mass transfer phenomena during the physical processes involved ^[1].

The heat capacity ratio or adiabatic index or ratio of specific heats, is the ratio of heat capacity at constant pressure () to heat capacity at constant volume (). It is sometimes also known as the isentropic expansion factor ^[5]:

（1）

It can be rather difficult to find tabulated information for , since is more commonly tabulated. The following relation, can be used to determine ^[5]:

（2）

Values based on approximations (particularly — = R ) are in many cases not sufficiently accurate for practical engineering calculations such as flow rates through pipes and valves. An experimental value should be used rather than one based on this approximation, where possible. A rigorous value for the heat capacity ratiocan also be calculated by determining from the residual properties expressed as ^[6]:

（3）

Values for are readily available and recorded, but values for need to be determined via relations such as these. Gaskell ^[7] referred to the derivation of the thermodynamic relations between the heat capacities. The above definition is the approach used to develop rigorous expressions from equations of state (such as