a. sheikhzadeh

Groundwater is a vital resource that supplies water needs for various purposes. In recent years, with the increase in population growth, the demand for water along with climate change have led to excessive extraction of underground water and the quantitative and qualitative reduction of this valuable resource at the global level. With the increasing understanding of the interdependence of water and development, paying attention to the sustainable management of underground water in shared boundary aquifers to deal with threats such as lack of water, food, energy, loss of ecosystems and biodiversity and most importantly a decrease in human security, is a must-do act. Therefore, in order to achieve an increase in the level of cooperation for the fair and sustainable use of the country's shared boundary aquifers and also to prevent any disputes and conflicts in the future, the successful experiences of international cooperation between shared boundary aquifers such as the Geneva Aquifer Agreement (between France and Switzerland) has been used and suggestions have been made in this regard. The proposed solution includes an initial agreement contract for more cooperation in the field of identifying technical, socio-cultural, political, economic and legal parameters with the participation and activity of all governmental and non-governmental organizations, technical and specialist experts, academic and civil communities as a common set, provision of financial resources to achieve a comprehensive study of the common aquifer status, sharing reliable information in a common base, stablishing an organization agreed by the beneficiary countries and defining the necessary laws and obligations, forming an advisory committee in order to reduce disputes and to monitor the implementation of commitments, and finally, presenting a comprehensive framework in the form of a shared agreement between the beneficiary countries with a common aquifer.

Today, increasing the efficiency and optimization of energy systems in terms of economic and environmental conditions is of particular importance. So far, several methods have been proposed to increase the heat transfer in thermal systems, including the use of nanofluids and types of fluid flow turbulators. In this research, the application of both nanofluid and twisted tape to improve the heat transfer coefficient were numerically investigated. Different turbulence models were used to simulate fluid turbulence. The results showed that increasing the nanoparticle volume fraction, reducing the twisting ratio, and increasing the Reynolds number resulted in an increase in heat transfer. By reducing the twisting ratio from 15 to 5, the heat transfer rate increases from 8-16%. With rising Reynolds number from 10,000 to 20,000, maximum temperature differences decreases by 4.5%. Moving downstream of the flow, the difference between the maximum temperature of the sections decreases. Increasing the heat transfer and intensifying the effects of the twisted tape to downward are the reasons for this decline.

The single-phase flow and thermal performance of a double pipe heat exchanger are examined by experimental methods. The working fluid is water at atmospheric pressure. Temperature measurements at the inlet and outlet of the two streams and also at an intermediate point half way between the inlet and outlet is made, using copper-constantan thermocouple wires. Mass flow rates for each stream are also measured using calibrated rotameters. Heat is supplied to the inner tube stream by an immersion heater. The overall heat transfer coefficients are inferred from the measured data. The heat transfer coefficient of the inner tube flow (circular cross section) is calculated using the standard correlations. The heat transfer coefficient of the outer tube flow (annular cross section) is then deduced. Higher heat transfer coefficients are reported in the laminar flow regime in comparison to the predictions of standard correlations for straight and smooth tubes. The reasons for this discrepancy are identified and discussed. Experimental errors in measuring temperatures and mass flow rates are studied and their effects on the heat transfer coefficients are estimated. Experimental results for the range of operating conditions used in this work show that the outer tube side heat transfer coefficients are smaller than the inner side heat transfer coefficients by a factor of almost 1.5 and 3.4 in counter flow and parallel flow arrangements, respectively. The agreement with predictions is very good for the counter flow arrangement, but not very good for the parallel flow arrangement.