Prediction of compressed air transport properties at elevated pressures and high temperatures using simple method Alireza Bahadori ⇑ Curtin University, School of Chemical and Petroleum Engineering, GPO Box U1987, Perth, WA 6845, Australia article info Article history: Received 30 July 2010 Received in revised form 14 October 2010 Accepted 24 October 2010 Available online 13 November 2010 Keywords: Transport properties Thermal conductivity Viscosity Compressed air Arrhenius function abstract Compressed air energy storage is a way to store energy generated at one time for use at another time. At utility scale, energy generated during periods of low energy demand can be released to meet higher demand periods. Also compressed air is a commonly used utility across most manufacturing and process- ing industries as its production and handling are safe and easy. Compressed air systems are critical and play a pivotal role in the proper operation of many processing facilities since most of the instruments and controls depend on pressurized instrumentation air for operation. In this work, a simple predictive tool, which is easier than current available models involving a large number of parameters, requiring more complicated and longer computations, is presented here for the prediction of transport properties (namely thermal conductivity and viscosity) of compressed air at elevated pressures as a function of tem- perature and pressure using a simple Arrhenius-type function. The proposed correlation predicts the transport properties of air for temperature range between 260 and 1000 K, and pressures up to 1000 bar (100 MPa). Estimations are found to be in excellent agreement with the reliable data in the lit- erature with average absolute deviation being around 1.28% and 0.68% for thermal conductivity and vis- cosity respectively. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Energy storage systems are becoming more important for load leveling, especially for widespread use of intermittent renewable energy. Compressed air energy storage (CAES) is a promising meth- od for energy storage [1]. Interest in energy storage is now on the rise, especially for matching intermittent renewable energy with customer demand, as well as for storing excess nuclear or thermal power during the daily cycle. Compressed air energy storage (CAES) is a promising method for energy storage, with high effi- ciency and environmental friendliness [1–6]. Furthermore, process design of production and distribution of compressed air systems is very important to cover the process requirement and design guide for plant and instrument air systems as applicable to various processing industries [7]. Applications requiring accurate position control are in increasing use in indus- tries. Pneumatic servo systems can provide a clean, accurate, ro- bust positioning system [8]. Compressed air is a commonly used utility across most manufacturing and processing industries [9]. The energy savings gained through optimization of a compressed air system (CAS) can be substantial in dollar terms, yet several orders of magnitude lower than the potential costs incurs through system failures [10]. Compressed air is regarded as the fourth util- ity, after electricity, natural gas, and water, in facilitating produc- tion activities in industrial environment [11]. In manufacturing plants, compressed air is widely used for operations such as actu- ating, cleaning, cooling, drying parts, and removing metal chips. In addition, as a form of energy, compressed air represents no fire or explosion hazards; as the most natural of substances, it is clean and safe and regarded as totally green [12]. 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 [13]. These scientific fields of applica- tion and the corresponding investigations mainly refer either to low temperatures [14–17], or to relatively higher temperatures. [18], such as air properties in the temperature range between 100 and 200 °C. However, the knowledge of properties at wide range 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. The present study discusses the formulation of a novel and simple-to-use predictive tool which can be of significant impor- tance for the engineers. The predictive tool is of practical value 0306-2619/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.apenergy.2010.10.029 ⇑ Tel.: +61 8 9266 1782; fax: +61 8 9266 2681. E-mail addresses: alireza.bahadori@postgrad.curtin.edu.au, bahadori.alireza@ gmail.com Applied Energy 88 (2011) 1434–1440 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy