Mechanical Engineering
Mahmoud Afshar; Hamid Rad
Abstract
In this paper, an advanced analysis of a novel hybrid compression-absorption refrigeration system (HCARS) for natural gas dew point control unit in a gas refinery is presented. This unit separates the heavy hydrocarbon molecules in the natural gas, which is traditionally carried out by natural gas cooling ...
Read More
In this paper, an advanced analysis of a novel hybrid compression-absorption refrigeration system (HCARS) for natural gas dew point control unit in a gas refinery is presented. This unit separates the heavy hydrocarbon molecules in the natural gas, which is traditionally carried out by natural gas cooling in a compression refrigeration cycle (CRS). The power input required for the refrigeration cycle compressors is usually provided by gas turbines. The low efficiency of gas turbines and the excessive power required for running the CRS compressors have made it crucial to investigate different means to decrease the energy consumption of this cooling system. The waste heat of gas turbines flue gas can be recovered and utilized as the heating source for running an absorption refrigeration system (ARS) to provide part of the needed cooling load; hence, a hybrid compression absorption refrigeration system (HCARS) is launched. In this work, the application of HCARS is extended to the Fajr-e-Jam gas refinery currently operating with a CRS, and an advanced exergetic analysis of the proposed ARS is performed to further improve the proposed system. The effect of different variables on the performance of the proposed HCARS is also inspected. The proposed system and these analyses are novel for the gas refinery dew point control unit. Real CRS operational data are utilized in all the investigations, and proper means are presented for the validation of the simulation results. The proposed system resulted in 63% additional cooling capacity of the HCARS (12550 KW) in comparison to the current CRS (7670 kW) for the equal natural gas consumption, which overall saves about 50000 SCMD of natural gas. Based on the exergy analysis of all the equipment, the exergy efficiency of the proposed ARS is 0.155. In addition, the parametric study of the effects of the gas turbine flue gas exit temperature and flow rate, ambient temperature, partial load operation of CRS, absorption solution flow rate, and concentration on the HCARS performance is carried out. These studies should provide the information needed for operating the proposed system in different situations.
Management
Abbas Alimoradi; Sepideh Borzoupour
Abstract
In the present business atmosphere, an organization should be able to respond to environmental needs occasioned by rapid and dynamic evolution as quickly as possible. It is obvious that such ability is impossible without a proper strategic approach, strategic thinking, and a suitable management accounting ...
Read More
In the present business atmosphere, an organization should be able to respond to environmental needs occasioned by rapid and dynamic evolution as quickly as possible. It is obvious that such ability is impossible without a proper strategic approach, strategic thinking, and a suitable management accounting system. This study attempts to investigate the relationships between strategy, management accounting systems, and the performance of Iranian petrochemical companies under the framework of contingency theory. It is assumed that matches between organizational strategies and the content variables of organizational structure in controlling environments such as management accounting systems could produce an optimal level of performance. The statistical population of the study is Iranian petrochemical private companies, and the required information has been gathered by questionnaire the internal reliability of which is confirmed by a Cronbach's alpha coefficient of 83.4%. Structural equation modelling with LISREL software has been used for data analysis and hypotheses testing. The results not only confirm the direct association between strategy, management accounting systems, and company performance, but also support the effect of management accounting system as a mediating variable on the relationship between strategy and performance. According to the results, it might be concluded that contingency theory postulates are applicable to the Iranian petrochemical industry, and this conclusion may shed some light on the way in which these companies are managed and controlled.
